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|
// SPDX-License-Identifier: GPL-2.0+
/*
* SSH packet transport layer.
*
* Copyright (C) 2019-2020 Maximilian Luz <luzmaximilian@gmail.com>
*/
#include <asm/unaligned.h>
#include <linux/atomic.h>
#include <linux/error-injection.h>
#include <linux/jiffies.h>
#include <linux/kfifo.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/ktime.h>
#include <linux/limits.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/serdev.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/surface_aggregator/serial_hub.h>
#include "ssh_msgb.h"
#include "ssh_packet_layer.h"
#include "ssh_parser.h"
#include "trace.h"
/*
* To simplify reasoning about the code below, we define a few concepts. The
* system below is similar to a state-machine for packets, however, there are
* too many states to explicitly write them down. To (somewhat) manage the
* states and packets we rely on flags, reference counting, and some simple
* concepts. State transitions are triggered by actions.
*
* >> Actions <<
*
* - submit
* - transmission start (process next item in queue)
* - transmission finished (guaranteed to never be parallel to transmission
* start)
* - ACK received
* - NAK received (this is equivalent to issuing re-submit for all pending
* packets)
* - timeout (this is equivalent to re-issuing a submit or canceling)
* - cancel (non-pending and pending)
*
* >> Data Structures, Packet Ownership, General Overview <<
*
* The code below employs two main data structures: The packet queue,
* containing all packets scheduled for transmission, and the set of pending
* packets, containing all packets awaiting an ACK.
*
* Shared ownership of a packet is controlled via reference counting. Inside
* the transport system are a total of five packet owners:
*
* - the packet queue,
* - the pending set,
* - the transmitter thread,
* - the receiver thread (via ACKing), and
* - the timeout work item.
*
* Normal operation is as follows: The initial reference of the packet is
* obtained by submitting the packet and queuing it. The receiver thread takes
* packets from the queue. By doing this, it does not increment the refcount
* but takes over the reference (removing it from the queue). If the packet is
* sequenced (i.e. needs to be ACKed by the client), the transmitter thread
* sets-up the timeout and adds the packet to the pending set before starting
* to transmit it. As the timeout is handled by a reaper task, no additional
* reference for it is needed. After the transmit is done, the reference held
* by the transmitter thread is dropped. If the packet is unsequenced (i.e.
* does not need an ACK), the packet is completed by the transmitter thread
* before dropping that reference.
*
* On receival of an ACK, the receiver thread removes and obtains the
* reference to the packet from the pending set. The receiver thread will then
* complete the packet and drop its reference.
*
* On receival of a NAK, the receiver thread re-submits all currently pending
* packets.
*
* Packet timeouts are detected by the timeout reaper. This is a task,
* scheduled depending on the earliest packet timeout expiration date,
* checking all currently pending packets if their timeout has expired. If the
* timeout of a packet has expired, it is re-submitted and the number of tries
* of this packet is incremented. If this number reaches its limit, the packet
* will be completed with a failure.
*
* On transmission failure (such as repeated packet timeouts), the completion
* callback is immediately run by on thread on which the error was detected.
*
* To ensure that a packet eventually leaves the system it is marked as
* "locked" directly before it is going to be completed or when it is
* canceled. Marking a packet as "locked" has the effect that passing and
* creating new references of the packet is disallowed. This means that the
* packet cannot be added to the queue, the pending set, and the timeout, or
* be picked up by the transmitter thread or receiver thread. To remove a
* packet from the system it has to be marked as locked and subsequently all
* references from the data structures (queue, pending) have to be removed.
* References held by threads will eventually be dropped automatically as
* their execution progresses.
*
* Note that the packet completion callback is, in case of success and for a
* sequenced packet, guaranteed to run on the receiver thread, thus providing
* a way to reliably identify responses to the packet. The packet completion
* callback is only run once and it does not indicate that the packet has
* fully left the system (for this, one should rely on the release method,
* triggered when the reference count of the packet reaches zero). In case of
* re-submission (and with somewhat unlikely timing), it may be possible that
* the packet is being re-transmitted while the completion callback runs.
* Completion will occur both on success and internal error, as well as when
* the packet is canceled.
*
* >> Flags <<
*
* Flags are used to indicate the state and progression of a packet. Some flags
* have stricter guarantees than other:
*
* - locked
* Indicates if the packet is locked. If the packet is locked, passing and/or
* creating additional references to the packet is forbidden. The packet thus
* may not be queued, dequeued, or removed or added to the pending set. Note
* that the packet state flags may still change (e.g. it may be marked as
* ACKed, transmitted, ...).
*
* - completed
* Indicates if the packet completion callback has been executed or is about
* to be executed. This flag is used to ensure that the packet completion
* callback is only run once.
*
* - queued
* Indicates if a packet is present in the submission queue or not. This flag
* must only be modified with the queue lock held, and must be coherent to the
* presence of the packet in the queue.
*
* - pending
* Indicates if a packet is present in the set of pending packets or not.
* This flag must only be modified with the pending lock held, and must be
* coherent to the presence of the packet in the pending set.
*
* - transmitting
* Indicates if the packet is currently transmitting. In case of
* re-transmissions, it is only safe to wait on the "transmitted" completion
* after this flag has been set. The completion will be set both in success
* and error case.
*
* - transmitted
* Indicates if the packet has been transmitted. This flag is not cleared by
* the system, thus it indicates the first transmission only.
*
* - acked
* Indicates if the packet has been acknowledged by the client. There are no
* other guarantees given. For example, the packet may still be canceled
* and/or the completion may be triggered an error even though this bit is
* set. Rely on the status provided to the completion callback instead.
*
* - canceled
* Indicates if the packet has been canceled from the outside. There are no
* other guarantees given. Specifically, the packet may be completed by
* another part of the system before the cancellation attempts to complete it.
*
* >> General Notes <<
*
* - To avoid deadlocks, if both queue and pending locks are required, the
* pending lock must be acquired before the queue lock.
*
* - The packet priority must be accessed only while holding the queue lock.
*
* - The packet timestamp must be accessed only while holding the pending
* lock.
*/
/*
* SSH_PTL_MAX_PACKET_TRIES - Maximum transmission attempts for packet.
*
* Maximum number of transmission attempts per sequenced packet in case of
* time-outs. Must be smaller than 16. If the packet times out after this
* amount of tries, the packet will be completed with %-ETIMEDOUT as status
* code.
*/
#define SSH_PTL_MAX_PACKET_TRIES 3
/*
* SSH_PTL_TX_TIMEOUT - Packet transmission timeout.
*
* Timeout in jiffies for packet transmission via the underlying serial
* device. If transmitting the packet takes longer than this timeout, the
* packet will be completed with -ETIMEDOUT. It will not be re-submitted.
*/
#define SSH_PTL_TX_TIMEOUT HZ
/*
* SSH_PTL_PACKET_TIMEOUT - Packet response timeout.
*
* Timeout as ktime_t delta for ACKs. If we have not received an ACK in this
* time-frame after starting transmission, the packet will be re-submitted.
*/
#define SSH_PTL_PACKET_TIMEOUT ms_to_ktime(1000)
/*
* SSH_PTL_PACKET_TIMEOUT_RESOLUTION - Packet timeout granularity.
*
* Time-resolution for timeouts. Should be larger than one jiffy to avoid
* direct re-scheduling of reaper work_struct.
*/
#define SSH_PTL_PACKET_TIMEOUT_RESOLUTION ms_to_ktime(max(2000 / HZ, 50))
/*
* SSH_PTL_MAX_PENDING - Maximum number of pending packets.
*
* Maximum number of sequenced packets concurrently waiting for an ACK.
* Packets marked as blocking will not be transmitted while this limit is
* reached.
*/
#define SSH_PTL_MAX_PENDING 1
/*
* SSH_PTL_RX_BUF_LEN - Evaluation-buffer size in bytes.
*/
#define SSH_PTL_RX_BUF_LEN 4096
/*
* SSH_PTL_RX_FIFO_LEN - Fifo input-buffer size in bytes.
*/
#define SSH_PTL_RX_FIFO_LEN 4096
#ifdef CONFIG_SURFACE_AGGREGATOR_ERROR_INJECTION
/**
* ssh_ptl_should_drop_ack_packet() - Error injection hook to drop ACK packets.
*
* Useful to test detection and handling of automated re-transmits by the EC.
* Specifically of packets that the EC considers not-ACKed but the driver
* already considers ACKed (due to dropped ACK). In this case, the EC
* re-transmits the packet-to-be-ACKed and the driver should detect it as
* duplicate/already handled. Note that the driver should still send an ACK
* for the re-transmitted packet.
*/
static noinline bool ssh_ptl_should_drop_ack_packet(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_drop_ack_packet, TRUE);
/**
* ssh_ptl_should_drop_nak_packet() - Error injection hook to drop NAK packets.
*
* Useful to test/force automated (timeout-based) re-transmit by the EC.
* Specifically, packets that have not reached the driver completely/with valid
* checksums. Only useful in combination with receival of (injected) bad data.
*/
static noinline bool ssh_ptl_should_drop_nak_packet(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_drop_nak_packet, TRUE);
/**
* ssh_ptl_should_drop_dsq_packet() - Error injection hook to drop sequenced
* data packet.
*
* Useful to test re-transmit timeout of the driver. If the data packet has not
* been ACKed after a certain time, the driver should re-transmit the packet up
* to limited number of times defined in SSH_PTL_MAX_PACKET_TRIES.
*/
static noinline bool ssh_ptl_should_drop_dsq_packet(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_drop_dsq_packet, TRUE);
/**
* ssh_ptl_should_fail_write() - Error injection hook to make
* serdev_device_write() fail.
*
* Hook to simulate errors in serdev_device_write when transmitting packets.
*/
static noinline int ssh_ptl_should_fail_write(void)
{
return 0;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_fail_write, ERRNO);
/**
* ssh_ptl_should_corrupt_tx_data() - Error injection hook to simulate invalid
* data being sent to the EC.
*
* Hook to simulate corrupt/invalid data being sent from host (driver) to EC.
* Causes the packet data to be actively corrupted by overwriting it with
* pre-defined values, such that it becomes invalid, causing the EC to respond
* with a NAK packet. Useful to test handling of NAK packets received by the
* driver.
*/
static noinline bool ssh_ptl_should_corrupt_tx_data(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_corrupt_tx_data, TRUE);
/**
* ssh_ptl_should_corrupt_rx_syn() - Error injection hook to simulate invalid
* data being sent by the EC.
*
* Hook to simulate invalid SYN bytes, i.e. an invalid start of messages and
* test handling thereof in the driver.
*/
static noinline bool ssh_ptl_should_corrupt_rx_syn(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_corrupt_rx_syn, TRUE);
/**
* ssh_ptl_should_corrupt_rx_data() - Error injection hook to simulate invalid
* data being sent by the EC.
*
* Hook to simulate invalid data/checksum of the message frame and test handling
* thereof in the driver.
*/
static noinline bool ssh_ptl_should_corrupt_rx_data(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_ptl_should_corrupt_rx_data, TRUE);
static bool __ssh_ptl_should_drop_ack_packet(struct ssh_packet *packet)
{
if (likely(!ssh_ptl_should_drop_ack_packet()))
return false;
trace_ssam_ei_tx_drop_ack_packet(packet);
ptl_info(packet->ptl, "packet error injection: dropping ACK packet %p\n",
packet);
return true;
}
static bool __ssh_ptl_should_drop_nak_packet(struct ssh_packet *packet)
{
if (likely(!ssh_ptl_should_drop_nak_packet()))
return false;
trace_ssam_ei_tx_drop_nak_packet(packet);
ptl_info(packet->ptl, "packet error injection: dropping NAK packet %p\n",
packet);
return true;
}
static bool __ssh_ptl_should_drop_dsq_packet(struct ssh_packet *packet)
{
if (likely(!ssh_ptl_should_drop_dsq_packet()))
return false;
trace_ssam_ei_tx_drop_dsq_packet(packet);
ptl_info(packet->ptl,
"packet error injection: dropping sequenced data packet %p\n",
packet);
return true;
}
static bool ssh_ptl_should_drop_packet(struct ssh_packet *packet)
{
/* Ignore packets that don't carry any data (i.e. flush). */
if (!packet->data.ptr || !packet->data.len)
return false;
switch (packet->data.ptr[SSH_MSGOFFSET_FRAME(type)]) {
case SSH_FRAME_TYPE_ACK:
return __ssh_ptl_should_drop_ack_packet(packet);
case SSH_FRAME_TYPE_NAK:
return __ssh_ptl_should_drop_nak_packet(packet);
case SSH_FRAME_TYPE_DATA_SEQ:
return __ssh_ptl_should_drop_dsq_packet(packet);
default:
return false;
}
}
static int ssh_ptl_write_buf(struct ssh_ptl *ptl, struct ssh_packet *packet,
const unsigned char *buf, size_t count)
{
int status;
status = ssh_ptl_should_fail_write();
if (unlikely(status)) {
trace_ssam_ei_tx_fail_write(packet, status);
ptl_info(packet->ptl,
"packet error injection: simulating transmit error %d, packet %p\n",
status, packet);
return status;
}
return serdev_device_write_buf(ptl->serdev, buf, count);
}
static void ssh_ptl_tx_inject_invalid_data(struct ssh_packet *packet)
{
/* Ignore packets that don't carry any data (i.e. flush). */
if (!packet->data.ptr || !packet->data.len)
return;
/* Only allow sequenced data packets to be modified. */
if (packet->data.ptr[SSH_MSGOFFSET_FRAME(type)] != SSH_FRAME_TYPE_DATA_SEQ)
return;
if (likely(!ssh_ptl_should_corrupt_tx_data()))
return;
trace_ssam_ei_tx_corrupt_data(packet);
ptl_info(packet->ptl,
"packet error injection: simulating invalid transmit data on packet %p\n",
packet);
/*
* NB: The value 0xb3 has been chosen more or less randomly so that it
* doesn't have any (major) overlap with the SYN bytes (aa 55) and is
* non-trivial (i.e. non-zero, non-0xff).
*/
memset(packet->data.ptr, 0xb3, packet->data.len);
}
static void ssh_ptl_rx_inject_invalid_syn(struct ssh_ptl *ptl,
struct ssam_span *data)
{
struct ssam_span frame;
/* Check if there actually is something to corrupt. */
if (!sshp_find_syn(data, &frame))
return;
if (likely(!ssh_ptl_should_corrupt_rx_syn()))
return;
trace_ssam_ei_rx_corrupt_syn(data->len);
data->ptr[1] = 0xb3; /* Set second byte of SYN to "random" value. */
}
static void ssh_ptl_rx_inject_invalid_data(struct ssh_ptl *ptl,
struct ssam_span *frame)
{
size_t payload_len, message_len;
struct ssh_frame *sshf;
/* Ignore incomplete messages, will get handled once it's complete. */
if (frame->len < SSH_MESSAGE_LENGTH(0))
return;
/* Ignore incomplete messages, part 2. */
payload_len = get_unaligned_le16(&frame->ptr[SSH_MSGOFFSET_FRAME(len)]);
message_len = SSH_MESSAGE_LENGTH(payload_len);
if (frame->len < message_len)
return;
if (likely(!ssh_ptl_should_corrupt_rx_data()))
return;
sshf = (struct ssh_frame *)&frame->ptr[SSH_MSGOFFSET_FRAME(type)];
trace_ssam_ei_rx_corrupt_data(sshf);
/*
* Flip bits in first byte of payload checksum. This is basically
* equivalent to a payload/frame data error without us having to worry
* about (the, arguably pretty small, probability of) accidental
* checksum collisions.
*/
frame->ptr[frame->len - 2] = ~frame->ptr[frame->len - 2];
}
#else /* CONFIG_SURFACE_AGGREGATOR_ERROR_INJECTION */
static inline bool ssh_ptl_should_drop_packet(struct ssh_packet *packet)
{
return false;
}
static inline int ssh_ptl_write_buf(struct ssh_ptl *ptl,
struct ssh_packet *packet,
const unsigned char *buf,
size_t count)
{
return serdev_device_write_buf(ptl->serdev, buf, count);
}
static inline void ssh_ptl_tx_inject_invalid_data(struct ssh_packet *packet)
{
}
static inline void ssh_ptl_rx_inject_invalid_syn(struct ssh_ptl *ptl,
struct ssam_span *data)
{
}
static inline void ssh_ptl_rx_inject_invalid_data(struct ssh_ptl *ptl,
struct ssam_span *frame)
{
}
#endif /* CONFIG_SURFACE_AGGREGATOR_ERROR_INJECTION */
static void __ssh_ptl_packet_release(struct kref *kref)
{
struct ssh_packet *p = container_of(kref, struct ssh_packet, refcnt);
trace_ssam_packet_release(p);
ptl_dbg_cond(p->ptl, "ptl: releasing packet %p\n", p);
p->ops->release(p);
}
/**
* ssh_packet_get() - Increment reference count of packet.
* @packet: The packet to increment the reference count of.
*
* Increments the reference count of the given packet. See ssh_packet_put()
* for the counter-part of this function.
*
* Return: Returns the packet provided as input.
*/
struct ssh_packet *ssh_packet_get(struct ssh_packet *packet)
{
if (packet)
kref_get(&packet->refcnt);
return packet;
}
EXPORT_SYMBOL_GPL(ssh_packet_get);
/**
* ssh_packet_put() - Decrement reference count of packet.
* @packet: The packet to decrement the reference count of.
*
* If the reference count reaches zero, the ``release`` callback specified in
* the packet's &struct ssh_packet_ops, i.e. ``packet->ops->release``, will be
* called.
*
* See ssh_packet_get() for the counter-part of this function.
*/
void ssh_packet_put(struct ssh_packet *packet)
{
if (packet)
kref_put(&packet->refcnt, __ssh_ptl_packet_release);
}
EXPORT_SYMBOL_GPL(ssh_packet_put);
static u8 ssh_packet_get_seq(struct ssh_packet *packet)
{
return packet->data.ptr[SSH_MSGOFFSET_FRAME(seq)];
}
/**
* ssh_packet_init() - Initialize SSH packet.
* @packet: The packet to initialize.
* @type: Type-flags of the packet.
* @priority: Priority of the packet. See SSH_PACKET_PRIORITY() for details.
* @ops: Packet operations.
*
* Initializes the given SSH packet. Sets the transmission buffer pointer to
* %NULL and the transmission buffer length to zero. For data-type packets,
* this buffer has to be set separately via ssh_packet_set_data() before
* submission, and must contain a valid SSH message, i.e. frame with optional
* payload of any type.
*/
void ssh_packet_init(struct ssh_packet *packet, unsigned long type,
u8 priority, const struct ssh_packet_ops *ops)
{
kref_init(&packet->refcnt);
packet->ptl = NULL;
INIT_LIST_HEAD(&packet->queue_node);
INIT_LIST_HEAD(&packet->pending_node);
packet->state = type & SSH_PACKET_FLAGS_TY_MASK;
packet->priority = priority;
packet->timestamp = KTIME_MAX;
packet->data.ptr = NULL;
packet->data.len = 0;
packet->ops = ops;
}
static struct kmem_cache *ssh_ctrl_packet_cache;
/**
* ssh_ctrl_packet_cache_init() - Initialize the control packet cache.
*/
int ssh_ctrl_packet_cache_init(void)
{
const unsigned int size = sizeof(struct ssh_packet) + SSH_MSG_LEN_CTRL;
const unsigned int align = __alignof__(struct ssh_packet);
struct kmem_cache *cache;
cache = kmem_cache_create("ssam_ctrl_packet", size, align, 0, NULL);
if (!cache)
return -ENOMEM;
ssh_ctrl_packet_cache = cache;
return 0;
}
/**
* ssh_ctrl_packet_cache_destroy() - Deinitialize the control packet cache.
*/
void ssh_ctrl_packet_cache_destroy(void)
{
kmem_cache_destroy(ssh_ctrl_packet_cache);
ssh_ctrl_packet_cache = NULL;
}
/**
* ssh_ctrl_packet_alloc() - Allocate packet from control packet cache.
* @packet: Where the pointer to the newly allocated packet should be stored.
* @buffer: The buffer corresponding to this packet.
* @flags: Flags used for allocation.
*
* Allocates a packet and corresponding transport buffer from the control
* packet cache. Sets the packet's buffer reference to the allocated buffer.
* The packet must be freed via ssh_ctrl_packet_free(), which will also free
* the corresponding buffer. The corresponding buffer must not be freed
* separately. Intended to be used with %ssh_ptl_ctrl_packet_ops as packet
* operations.
*
* Return: Returns zero on success, %-ENOMEM if the allocation failed.
*/
static int ssh_ctrl_packet_alloc(struct ssh_packet **packet,
struct ssam_span *buffer, gfp_t flags)
{
*packet = kmem_cache_alloc(ssh_ctrl_packet_cache, flags);
if (!*packet)
return -ENOMEM;
buffer->ptr = (u8 *)(*packet + 1);
buffer->len = SSH_MSG_LEN_CTRL;
trace_ssam_ctrl_packet_alloc(*packet, buffer->len);
return 0;
}
/**
* ssh_ctrl_packet_free() - Free packet allocated from control packet cache.
* @p: The packet to free.
*/
static void ssh_ctrl_packet_free(struct ssh_packet *p)
{
trace_ssam_ctrl_packet_free(p);
kmem_cache_free(ssh_ctrl_packet_cache, p);
}
static const struct ssh_packet_ops ssh_ptl_ctrl_packet_ops = {
.complete = NULL,
.release = ssh_ctrl_packet_free,
};
static void ssh_ptl_timeout_reaper_mod(struct ssh_ptl *ptl, ktime_t now,
ktime_t expires)
{
unsigned long delta = msecs_to_jiffies(ktime_ms_delta(expires, now));
ktime_t aexp = ktime_add(expires, SSH_PTL_PACKET_TIMEOUT_RESOLUTION);
spin_lock(&ptl->rtx_timeout.lock);
/* Re-adjust / schedule reaper only if it is above resolution delta. */
if (ktime_before(aexp, ptl->rtx_timeout.expires)) {
ptl->rtx_timeout.expires = expires;
mod_delayed_work(system_wq, &ptl->rtx_timeout.reaper, delta);
}
spin_unlock(&ptl->rtx_timeout.lock);
}
/* Must be called with queue lock held. */
static void ssh_packet_next_try(struct ssh_packet *p)
{
u8 base = ssh_packet_priority_get_base(p->priority);
u8 try = ssh_packet_priority_get_try(p->priority);
lockdep_assert_held(&p->ptl->queue.lock);
/*
* Ensure that we write the priority in one go via WRITE_ONCE() so we
* can access it via READ_ONCE() for tracing. Note that other access
* is guarded by the queue lock, so no need to use READ_ONCE() there.
*/
WRITE_ONCE(p->priority, __SSH_PACKET_PRIORITY(base, try + 1));
}
/* Must be called with queue lock held. */
static struct list_head *__ssh_ptl_queue_find_entrypoint(struct ssh_packet *p)
{
struct list_head *head;
struct ssh_packet *q;
lockdep_assert_held(&p->ptl->queue.lock);
/*
* We generally assume that there are less control (ACK/NAK) packets
* and re-submitted data packets as there are normal data packets (at
* least in situations in which many packets are queued; if there
* aren't many packets queued the decision on how to iterate should be
* basically irrelevant; the number of control/data packets is more or
* less limited via the maximum number of pending packets). Thus, when
* inserting a control or re-submitted data packet, (determined by
* their priority), we search from front to back. Normal data packets
* are, usually queued directly at the tail of the queue, so for those
* search from back to front.
*/
if (p->priority > SSH_PACKET_PRIORITY(DATA, 0)) {
list_for_each(head, &p->ptl->queue.head) {
q = list_entry(head, struct ssh_packet, queue_node);
if (q->priority < p->priority)
break;
}
} else {
list_for_each_prev(head, &p->ptl->queue.head) {
q = list_entry(head, struct ssh_packet, queue_node);
if (q->priority >= p->priority) {
head = head->next;
break;
}
}
}
return head;
}
/* Must be called with queue lock held. */
static int __ssh_ptl_queue_push(struct ssh_packet *packet)
{
struct ssh_ptl *ptl = packet->ptl;
struct list_head *head;
lockdep_assert_held(&ptl->queue.lock);
if (test_bit(SSH_PTL_SF_SHUTDOWN_BIT, &ptl->state))
return -ESHUTDOWN;
/* Avoid further transitions when canceling/completing. */
if (test_bit(SSH_PACKET_SF_LOCKED_BIT, &packet->state))
return -EINVAL;
/* If this packet has already been queued, do not add it. */
if (test_and_set_bit(SSH_PACKET_SF_QUEUED_BIT, &packet->state))
return -EALREADY;
head = __ssh_ptl_queue_find_entrypoint(packet);
list_add_tail(&ssh_packet_get(packet)->queue_node, head);
return 0;
}
static int ssh_ptl_queue_push(struct ssh_packet *packet)
{
int status;
spin_lock(&packet->ptl->queue.lock);
status = __ssh_ptl_queue_push(packet);
spin_unlock(&packet->ptl->queue.lock);
return status;
}
static void ssh_ptl_queue_remove(struct ssh_packet *packet)
{
struct ssh_ptl *ptl = packet->ptl;
spin_lock(&ptl->queue.lock);
if (!test_and_clear_bit(SSH_PACKET_SF_QUEUED_BIT, &packet->state)) {
spin_unlock(&ptl->queue.lock);
return;
}
list_del(&packet->queue_node);
spin_unlock(&ptl->queue.lock);
ssh_packet_put(packet);
}
static void ssh_ptl_pending_push(struct ssh_packet *p)
{
struct ssh_ptl *ptl = p->ptl;
const ktime_t timestamp = ktime_get_coarse_boottime();
const ktime_t timeout = ptl->rtx_timeout.timeout;
/*
* Note: We can get the time for the timestamp before acquiring the
* lock as this is the only place we're setting it and this function
* is called only from the transmitter thread. Thus it is not possible
* to overwrite the timestamp with an outdated value below.
*/
spin_lock(&ptl->pending.lock);
/* If we are canceling/completing this packet, do not add it. */
if (test_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state)) {
spin_unlock(&ptl->pending.lock);
return;
}
/*
* On re-submission, the packet has already been added the pending
* set. We still need to update the timestamp as the packet timeout is
* reset for each (re-)submission.
*/
p->timestamp = timestamp;
/* In case it is already pending (e.g. re-submission), do not add it. */
if (!test_and_set_bit(SSH_PACKET_SF_PENDING_BIT, &p->state)) {
atomic_inc(&ptl->pending.count);
list_add_tail(&ssh_packet_get(p)->pending_node, &ptl->pending.head);
}
spin_unlock(&ptl->pending.lock);
/* Arm/update timeout reaper. */
ssh_ptl_timeout_reaper_mod(ptl, timestamp, timestamp + timeout);
}
static void ssh_ptl_pending_remove(struct ssh_packet *packet)
{
struct ssh_ptl *ptl = packet->ptl;
spin_lock(&ptl->pending.lock);
if (!test_and_clear_bit(SSH_PACKET_SF_PENDING_BIT, &packet->state)) {
spin_unlock(&ptl->pending.lock);
return;
}
list_del(&packet->pending_node);
atomic_dec(&ptl->pending.count);
spin_unlock(&ptl->pending.lock);
ssh_packet_put(packet);
}
/* Warning: Does not check/set "completed" bit. */
static void __ssh_ptl_complete(struct ssh_packet *p, int status)
{
struct ssh_ptl *ptl = READ_ONCE(p->ptl);
trace_ssam_packet_complete(p, status);
ptl_dbg_cond(ptl, "ptl: completing packet %p (status: %d)\n", p, status);
if (p->ops->complete)
p->ops->complete(p, status);
}
static void ssh_ptl_remove_and_complete(struct ssh_packet *p, int status)
{
/*
* A call to this function should in general be preceded by
* set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->flags) to avoid re-adding the
* packet to the structures it's going to be removed from.
*
* The set_bit call does not need explicit memory barriers as the
* implicit barrier of the test_and_set_bit() call below ensure that the
* flag is visible before we actually attempt to remove the packet.
*/
if (test_and_set_bit(SSH_PACKET_SF_COMPLETED_BIT, &p->state))
return;
ssh_ptl_queue_remove(p);
ssh_ptl_pending_remove(p);
__ssh_ptl_complete(p, status);
}
static bool ssh_ptl_tx_can_process(struct ssh_packet *packet)
{
struct ssh_ptl *ptl = packet->ptl;
if (test_bit(SSH_PACKET_TY_FLUSH_BIT, &packet->state))
return !atomic_read(&ptl->pending.count);
/* We can always process non-blocking packets. */
if (!test_bit(SSH_PACKET_TY_BLOCKING_BIT, &packet->state))
return true;
/* If we are already waiting for this packet, send it again. */
if (test_bit(SSH_PACKET_SF_PENDING_BIT, &packet->state))
return true;
/* Otherwise: Check if we have the capacity to send. */
return atomic_read(&ptl->pending.count) < SSH_PTL_MAX_PENDING;
}
static struct ssh_packet *ssh_ptl_tx_pop(struct ssh_ptl *ptl)
{
struct ssh_packet *packet = ERR_PTR(-ENOENT);
struct ssh_packet *p, *n;
spin_lock(&ptl->queue.lock);
list_for_each_entry_safe(p, n, &ptl->queue.head, queue_node) {
/*
* If we are canceling or completing this packet, ignore it.
* It's going to be removed from this queue shortly.
*/
if (test_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state))
continue;
/*
* Packets should be ordered non-blocking/to-be-resent first.
* If we cannot process this packet, assume that we can't
* process any following packet either and abort.
*/
if (!ssh_ptl_tx_can_process(p)) {
packet = ERR_PTR(-EBUSY);
break;
}
/*
* We are allowed to change the state now. Remove it from the
* queue and mark it as being transmitted.
*/
list_del(&p->queue_node);
set_bit(SSH_PACKET_SF_TRANSMITTING_BIT, &p->state);
/* Ensure that state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_QUEUED_BIT, &p->state);
/*
* Update number of tries. This directly influences the
* priority in case the packet is re-submitted (e.g. via
* timeout/NAK). Note that all reads and writes to the
* priority after the first submission are guarded by the
* queue lock.
*/
ssh_packet_next_try(p);
packet = p;
break;
}
spin_unlock(&ptl->queue.lock);
return packet;
}
static struct ssh_packet *ssh_ptl_tx_next(struct ssh_ptl *ptl)
{
struct ssh_packet *p;
p = ssh_ptl_tx_pop(ptl);
if (IS_ERR(p))
return p;
if (test_bit(SSH_PACKET_TY_SEQUENCED_BIT, &p->state)) {
ptl_dbg(ptl, "ptl: transmitting sequenced packet %p\n", p);
ssh_ptl_pending_push(p);
} else {
ptl_dbg(ptl, "ptl: transmitting non-sequenced packet %p\n", p);
}
return p;
}
static void ssh_ptl_tx_compl_success(struct ssh_packet *packet)
{
struct ssh_ptl *ptl = packet->ptl;
ptl_dbg(ptl, "ptl: successfully transmitted packet %p\n", packet);
/* Transition state to "transmitted". */
set_bit(SSH_PACKET_SF_TRANSMITTED_BIT, &packet->state);
/* Ensure that state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_TRANSMITTING_BIT, &packet->state);
/* If the packet is unsequenced, we're done: Lock and complete. */
if (!test_bit(SSH_PACKET_TY_SEQUENCED_BIT, &packet->state)) {
set_bit(SSH_PACKET_SF_LOCKED_BIT, &packet->state);
ssh_ptl_remove_and_complete(packet, 0);
}
/*
* Notify that a packet transmission has finished. In general we're only
* waiting for one packet (if any), so wake_up_all should be fine.
*/
wake_up_all(&ptl->tx.packet_wq);
}
static void ssh_ptl_tx_compl_error(struct ssh_packet *packet, int status)
{
/* Transmission failure: Lock the packet and try to complete it. */
set_bit(SSH_PACKET_SF_LOCKED_BIT, &packet->state);
/* Ensure that state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_TRANSMITTING_BIT, &packet->state);
ptl_err(packet->ptl, "ptl: transmission error: %d\n", status);
ptl_dbg(packet->ptl, "ptl: failed to transmit packet: %p\n", packet);
ssh_ptl_remove_and_complete(packet, status);
/*
* Notify that a packet transmission has finished. In general we're only
* waiting for one packet (if any), so wake_up_all should be fine.
*/
wake_up_all(&packet->ptl->tx.packet_wq);
}
static long ssh_ptl_tx_wait_packet(struct ssh_ptl *ptl)
{
int status;
status = wait_for_completion_interruptible(&ptl->tx.thread_cplt_pkt);
reinit_completion(&ptl->tx.thread_cplt_pkt);
/*
* Ensure completion is cleared before continuing to avoid lost update
* problems.
*/
smp_mb__after_atomic();
return status;
}
static long ssh_ptl_tx_wait_transfer(struct ssh_ptl *ptl, long timeout)
{
long status;
status = wait_for_completion_interruptible_timeout(&ptl->tx.thread_cplt_tx,
timeout);
reinit_completion(&ptl->tx.thread_cplt_tx);
/*
* Ensure completion is cleared before continuing to avoid lost update
* problems.
*/
smp_mb__after_atomic();
return status;
}
static int ssh_ptl_tx_packet(struct ssh_ptl *ptl, struct ssh_packet *packet)
{
long timeout = SSH_PTL_TX_TIMEOUT;
size_t offset = 0;
/* Note: Flush-packets don't have any data. */
if (unlikely(!packet->data.ptr))
return 0;
/* Error injection: drop packet to simulate transmission problem. */
if (ssh_ptl_should_drop_packet(packet))
return 0;
/* Error injection: simulate invalid packet data. */
ssh_ptl_tx_inject_invalid_data(packet);
ptl_dbg(ptl, "tx: sending data (length: %zu)\n", packet->data.len);
print_hex_dump_debug("tx: ", DUMP_PREFIX_OFFSET, 16, 1,
packet->data.ptr, packet->data.len, false);
do {
ssize_t status, len;
u8 *buf;
buf = packet->data.ptr + offset;
len = packet->data.len - offset;
status = ssh_ptl_write_buf(ptl, packet, buf, len);
if (status < 0)
return status;
if (status == len)
return 0;
offset += status;
timeout = ssh_ptl_tx_wait_transfer(ptl, timeout);
if (kthread_should_stop() || !atomic_read(&ptl->tx.running))
return -ESHUTDOWN;
if (timeout < 0)
return -EINTR;
if (timeout == 0)
return -ETIMEDOUT;
} while (true);
}
static int ssh_ptl_tx_threadfn(void *data)
{
struct ssh_ptl *ptl = data;
while (!kthread_should_stop() && atomic_read(&ptl->tx.running)) {
struct ssh_packet *packet;
int status;
/* Try to get the next packet. */
packet = ssh_ptl_tx_next(ptl);
/* If no packet can be processed, we are done. */
if (IS_ERR(packet)) {
ssh_ptl_tx_wait_packet(ptl);
continue;
}
/* Transfer and complete packet. */
status = ssh_ptl_tx_packet(ptl, packet);
if (status)
ssh_ptl_tx_compl_error(packet, status);
else
ssh_ptl_tx_compl_success(packet);
ssh_packet_put(packet);
}
return 0;
}
/**
* ssh_ptl_tx_wakeup_packet() - Wake up packet transmitter thread for new
* packet.
* @ptl: The packet transport layer.
*
* Wakes up the packet transmitter thread, notifying it that a new packet has
* arrived and is ready for transfer. If the packet transport layer has been
* shut down, calls to this function will be ignored.
*/
static void ssh_ptl_tx_wakeup_packet(struct ssh_ptl *ptl)
{
if (test_bit(SSH_PTL_SF_SHUTDOWN_BIT, &ptl->state))
return;
complete(&ptl->tx.thread_cplt_pkt);
}
/**
* ssh_ptl_tx_start() - Start packet transmitter thread.
* @ptl: The packet transport layer.
*
* Return: Returns zero on success, a negative error code on failure.
*/
int ssh_ptl_tx_start(struct ssh_ptl *ptl)
{
atomic_set_release(&ptl->tx.running, 1);
ptl->tx.thread = kthread_run(ssh_ptl_tx_threadfn, ptl, "ssam_serial_hub-tx");
if (IS_ERR(ptl->tx.thread))
return PTR_ERR(ptl->tx.thread);
return 0;
}
/**
* ssh_ptl_tx_stop() - Stop packet transmitter thread.
* @ptl: The packet transport layer.
*
* Return: Returns zero on success, a negative error code on failure.
*/
int ssh_ptl_tx_stop(struct ssh_ptl *ptl)
{
int status = 0;
if (!IS_ERR_OR_NULL(ptl->tx.thread)) {
/* Tell thread to stop. */
atomic_set_release(&ptl->tx.running, 0);
/*
* Wake up thread in case it is paused. Do not use wakeup
* helpers as this may be called when the shutdown bit has
* already been set.
*/
complete(&ptl->tx.thread_cplt_pkt);
complete(&ptl->tx.thread_cplt_tx);
/* Finally, wait for thread to stop. */
status = kthread_stop(ptl->tx.thread);
ptl->tx.thread = NULL;
}
return status;
}
static struct ssh_packet *ssh_ptl_ack_pop(struct ssh_ptl *ptl, u8 seq_id)
{
struct ssh_packet *packet = ERR_PTR(-ENOENT);
struct ssh_packet *p, *n;
spin_lock(&ptl->pending.lock);
list_for_each_entry_safe(p, n, &ptl->pending.head, pending_node) {
/*
* We generally expect packets to be in order, so first packet
* to be added to pending is first to be sent, is first to be
* ACKed.
*/
if (unlikely(ssh_packet_get_seq(p) != seq_id))
continue;
/*
* In case we receive an ACK while handling a transmission
* error completion. The packet will be removed shortly.
*/
if (unlikely(test_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state))) {
packet = ERR_PTR(-EPERM);
break;
}
/*
* Mark the packet as ACKed and remove it from pending by
* removing its node and decrementing the pending counter.
*/
set_bit(SSH_PACKET_SF_ACKED_BIT, &p->state);
/* Ensure that state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_PENDING_BIT, &p->state);
atomic_dec(&ptl->pending.count);
list_del(&p->pending_node);
packet = p;
break;
}
spin_unlock(&ptl->pending.lock);
return packet;
}
static void ssh_ptl_wait_until_transmitted(struct ssh_packet *packet)
{
wait_event(packet->ptl->tx.packet_wq,
test_bit(SSH_PACKET_SF_TRANSMITTED_BIT, &packet->state) ||
test_bit(SSH_PACKET_SF_LOCKED_BIT, &packet->state));
}
static void ssh_ptl_acknowledge(struct ssh_ptl *ptl, u8 seq)
{
struct ssh_packet *p;
p = ssh_ptl_ack_pop(ptl, seq);
if (IS_ERR(p)) {
if (PTR_ERR(p) == -ENOENT) {
/*
* The packet has not been found in the set of pending
* packets.
*/
ptl_warn(ptl, "ptl: received ACK for non-pending packet\n");
} else {
/*
* The packet is pending, but we are not allowed to take
* it because it has been locked.
*/
WARN_ON(PTR_ERR(p) != -EPERM);
}
return;
}
ptl_dbg(ptl, "ptl: received ACK for packet %p\n", p);
/*
* It is possible that the packet has been transmitted, but the state
* has not been updated from "transmitting" to "transmitted" yet.
* In that case, we need to wait for this transition to occur in order
* to determine between success or failure.
*
* On transmission failure, the packet will be locked after this call.
* On success, the transmitted bit will be set.
*/
ssh_ptl_wait_until_transmitted(p);
/*
* The packet will already be locked in case of a transmission error or
* cancellation. Let the transmitter or cancellation issuer complete the
* packet.
*/
if (unlikely(test_and_set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state))) {
if (unlikely(!test_bit(SSH_PACKET_SF_TRANSMITTED_BIT, &p->state)))
ptl_err(ptl, "ptl: received ACK before packet had been fully transmitted\n");
ssh_packet_put(p);
return;
}
ssh_ptl_remove_and_complete(p, 0);
ssh_packet_put(p);
if (atomic_read(&ptl->pending.count) < SSH_PTL_MAX_PENDING)
ssh_ptl_tx_wakeup_packet(ptl);
}
/**
* ssh_ptl_submit() - Submit a packet to the transport layer.
* @ptl: The packet transport layer to submit the packet to.
* @p: The packet to submit.
*
* Submits a new packet to the transport layer, queuing it to be sent. This
* function should not be used for re-submission.
*
* Return: Returns zero on success, %-EINVAL if a packet field is invalid or
* the packet has been canceled prior to submission, %-EALREADY if the packet
* has already been submitted, or %-ESHUTDOWN if the packet transport layer
* has been shut down.
*/
int ssh_ptl_submit(struct ssh_ptl *ptl, struct ssh_packet *p)
{
struct ssh_ptl *ptl_old;
int status;
trace_ssam_packet_submit(p);
/* Validate packet fields. */
if (test_bit(SSH_PACKET_TY_FLUSH_BIT, &p->state)) {
if (p->data.ptr || test_bit(SSH_PACKET_TY_SEQUENCED_BIT, &p->state))
return -EINVAL;
} else if (!p->data.ptr) {
return -EINVAL;
}
/*
* The ptl reference only gets set on or before the first submission.
* After the first submission, it has to be read-only.
*
* Note that ptl may already be set from upper-layer request
* submission, thus we cannot expect it to be NULL.
*/
ptl_old = READ_ONCE(p->ptl);
if (!ptl_old)
WRITE_ONCE(p->ptl, ptl);
else if (WARN_ON(ptl_old != ptl))
return -EALREADY; /* Submitted on different PTL. */
status = ssh_ptl_queue_push(p);
if (status)
return status;
if (!test_bit(SSH_PACKET_TY_BLOCKING_BIT, &p->state) ||
(atomic_read(&ptl->pending.count) < SSH_PTL_MAX_PENDING))
ssh_ptl_tx_wakeup_packet(ptl);
return 0;
}
/*
* __ssh_ptl_resubmit() - Re-submit a packet to the transport layer.
* @packet: The packet to re-submit.
*
* Re-submits the given packet: Checks if it can be re-submitted and queues it
* if it can, resetting the packet timestamp in the process. Must be called
* with the pending lock held.
*
* Return: Returns %-ECANCELED if the packet has exceeded its number of tries,
* %-EINVAL if the packet has been locked, %-EALREADY if the packet is already
* on the queue, and %-ESHUTDOWN if the transmission layer has been shut down.
*/
static int __ssh_ptl_resubmit(struct ssh_packet *packet)
{
int status;
u8 try;
lockdep_assert_held(&packet->ptl->pending.lock);
trace_ssam_packet_resubmit(packet);
spin_lock(&packet->ptl->queue.lock);
/* Check if the packet is out of tries. */
try = ssh_packet_priority_get_try(packet->priority);
if (try >= SSH_PTL_MAX_PACKET_TRIES) {
spin_unlock(&packet->ptl->queue.lock);
return -ECANCELED;
}
status = __ssh_ptl_queue_push(packet);
if (status) {
/*
* An error here indicates that the packet has either already
* been queued, been locked, or the transport layer is being
* shut down. In all cases: Ignore the error.
*/
spin_unlock(&packet->ptl->queue.lock);
return status;
}
packet->timestamp = KTIME_MAX;
spin_unlock(&packet->ptl->queue.lock);
return 0;
}
static void ssh_ptl_resubmit_pending(struct ssh_ptl *ptl)
{
struct ssh_packet *p;
bool resub = false;
/*
* Note: We deliberately do not remove/attempt to cancel and complete
* packets that are out of tires in this function. The packet will be
* eventually canceled and completed by the timeout. Removing the packet
* here could lead to overly eager cancellation if the packet has not
* been re-transmitted yet but the tries-counter already updated (i.e
* ssh_ptl_tx_next() removed the packet from the queue and updated the
* counter, but re-transmission for the last try has not actually
* started yet).
*/
spin_lock(&ptl->pending.lock);
/* Re-queue all pending packets. */
list_for_each_entry(p, &ptl->pending.head, pending_node) {
/*
* Re-submission fails if the packet is out of tries, has been
* locked, is already queued, or the layer is being shut down.
* No need to re-schedule tx-thread in those cases.
*/
if (!__ssh_ptl_resubmit(p))
resub = true;
}
spin_unlock(&ptl->pending.lock);
if (resub)
ssh_ptl_tx_wakeup_packet(ptl);
}
/**
* ssh_ptl_cancel() - Cancel a packet.
* @p: The packet to cancel.
*
* Cancels a packet. There are no guarantees on when completion and release
* callbacks will be called. This may occur during execution of this function
* or may occur at any point later.
*
* Note that it is not guaranteed that the packet will actually be canceled if
* the packet is concurrently completed by another process. The only guarantee
* of this function is that the packet will be completed (with success,
* failure, or cancellation) and released from the transport layer in a
* reasonable time-frame.
*
* May be called before the packet has been submitted, in which case any later
* packet submission fails.
*/
void ssh_ptl_cancel(struct ssh_packet *p)
{
if (test_and_set_bit(SSH_PACKET_SF_CANCELED_BIT, &p->state))
return;
trace_ssam_packet_cancel(p);
/*
* Lock packet and commit with memory barrier. If this packet has
* already been locked, it's going to be removed and completed by
* another party, which should have precedence.
*/
if (test_and_set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state))
return;
/*
* By marking the packet as locked and employing the implicit memory
* barrier of test_and_set_bit, we have guaranteed that, at this point,
* the packet cannot be added to the queue any more.
*
* In case the packet has never been submitted, packet->ptl is NULL. If
* the packet is currently being submitted, packet->ptl may be NULL or
* non-NULL. Due marking the packet as locked above and committing with
* the memory barrier, we have guaranteed that, if packet->ptl is NULL,
* the packet will never be added to the queue. If packet->ptl is
* non-NULL, we don't have any guarantees.
*/
if (READ_ONCE(p->ptl)) {
ssh_ptl_remove_and_complete(p, -ECANCELED);
if (atomic_read(&p->ptl->pending.count) < SSH_PTL_MAX_PENDING)
ssh_ptl_tx_wakeup_packet(p->ptl);
} else if (!test_and_set_bit(SSH_PACKET_SF_COMPLETED_BIT, &p->state)) {
__ssh_ptl_complete(p, -ECANCELED);
}
}
/* Must be called with pending lock held */
static ktime_t ssh_packet_get_expiration(struct ssh_packet *p, ktime_t timeout)
{
lockdep_assert_held(&p->ptl->pending.lock);
if (p->timestamp != KTIME_MAX)
return ktime_add(p->timestamp, timeout);
else
return KTIME_MAX;
}
static void ssh_ptl_timeout_reap(struct work_struct *work)
{
struct ssh_ptl *ptl = to_ssh_ptl(work, rtx_timeout.reaper.work);
struct ssh_packet *p, *n;
LIST_HEAD(claimed);
ktime_t now = ktime_get_coarse_boottime();
ktime_t timeout = ptl->rtx_timeout.timeout;
ktime_t next = KTIME_MAX;
bool resub = false;
int status;
trace_ssam_ptl_timeout_reap(atomic_read(&ptl->pending.count));
/*
* Mark reaper as "not pending". This is done before checking any
* packets to avoid lost-update type problems.
*/
spin_lock(&ptl->rtx_timeout.lock);
ptl->rtx_timeout.expires = KTIME_MAX;
spin_unlock(&ptl->rtx_timeout.lock);
spin_lock(&ptl->pending.lock);
list_for_each_entry_safe(p, n, &ptl->pending.head, pending_node) {
ktime_t expires = ssh_packet_get_expiration(p, timeout);
/*
* Check if the timeout hasn't expired yet. Find out next
* expiration date to be handled after this run.
*/
if (ktime_after(expires, now)) {
next = ktime_before(expires, next) ? expires : next;
continue;
}
trace_ssam_packet_timeout(p);
status = __ssh_ptl_resubmit(p);
/*
* Re-submission fails if the packet is out of tries, has been
* locked, is already queued, or the layer is being shut down.
* No need to re-schedule tx-thread in those cases.
*/
if (!status)
resub = true;
/* Go to next packet if this packet is not out of tries. */
if (status != -ECANCELED)
continue;
/* No more tries left: Cancel the packet. */
/*
* If someone else has locked the packet already, don't use it
* and let the other party complete it.
*/
if (test_and_set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state))
continue;
/*
* We have now marked the packet as locked. Thus it cannot be
* added to the pending list again after we've removed it here.
* We can therefore re-use the pending_node of this packet
* temporarily.
*/
clear_bit(SSH_PACKET_SF_PENDING_BIT, &p->state);
atomic_dec(&ptl->pending.count);
list_del(&p->pending_node);
list_add_tail(&p->pending_node, &claimed);
}
spin_unlock(&ptl->pending.lock);
/* Cancel and complete the packet. */
list_for_each_entry_safe(p, n, &claimed, pending_node) {
if (!test_and_set_bit(SSH_PACKET_SF_COMPLETED_BIT, &p->state)) {
ssh_ptl_queue_remove(p);
__ssh_ptl_complete(p, -ETIMEDOUT);
}
/*
* Drop the reference we've obtained by removing it from
* the pending set.
*/
list_del(&p->pending_node);
ssh_packet_put(p);
}
/* Ensure that reaper doesn't run again immediately. */
next = max(next, ktime_add(now, SSH_PTL_PACKET_TIMEOUT_RESOLUTION));
if (next != KTIME_MAX)
ssh_ptl_timeout_reaper_mod(ptl, now, next);
if (resub)
ssh_ptl_tx_wakeup_packet(ptl);
}
static bool ssh_ptl_rx_retransmit_check(struct ssh_ptl *ptl, u8 seq)
{
int i;
/*
* Check if SEQ has been seen recently (i.e. packet was
* re-transmitted and we should ignore it).
*/
for (i = 0; i < ARRAY_SIZE(ptl->rx.blocked.seqs); i++) {
if (likely(ptl->rx.blocked.seqs[i] != seq))
continue;
ptl_dbg(ptl, "ptl: ignoring repeated data packet\n");
return true;
}
/* Update list of blocked sequence IDs. */
ptl->rx.blocked.seqs[ptl->rx.blocked.offset] = seq;
ptl->rx.blocked.offset = (ptl->rx.blocked.offset + 1)
% ARRAY_SIZE(ptl->rx.blocked.seqs);
return false;
}
static void ssh_ptl_rx_dataframe(struct ssh_ptl *ptl,
const struct ssh_frame *frame,
const struct ssam_span *payload)
{
if (ssh_ptl_rx_retransmit_check(ptl, frame->seq))
return;
ptl->ops.data_received(ptl, payload);
}
static void ssh_ptl_send_ack(struct ssh_ptl *ptl, u8 seq)
{
struct ssh_packet *packet;
struct ssam_span buf;
struct msgbuf msgb;
int status;
status = ssh_ctrl_packet_alloc(&packet, &buf, GFP_KERNEL);
if (status) {
ptl_err(ptl, "ptl: failed to allocate ACK packet\n");
return;
}
ssh_packet_init(packet, 0, SSH_PACKET_PRIORITY(ACK, 0),
&ssh_ptl_ctrl_packet_ops);
msgb_init(&msgb, buf.ptr, buf.len);
msgb_push_ack(&msgb, seq);
ssh_packet_set_data(packet, msgb.begin, msgb_bytes_used(&msgb));
ssh_ptl_submit(ptl, packet);
ssh_packet_put(packet);
}
static void ssh_ptl_send_nak(struct ssh_ptl *ptl)
{
struct ssh_packet *packet;
struct ssam_span buf;
struct msgbuf msgb;
int status;
status = ssh_ctrl_packet_alloc(&packet, &buf, GFP_KERNEL);
if (status) {
ptl_err(ptl, "ptl: failed to allocate NAK packet\n");
return;
}
ssh_packet_init(packet, 0, SSH_PACKET_PRIORITY(NAK, 0),
&ssh_ptl_ctrl_packet_ops);
msgb_init(&msgb, buf.ptr, buf.len);
msgb_push_nak(&msgb);
ssh_packet_set_data(packet, msgb.begin, msgb_bytes_used(&msgb));
ssh_ptl_submit(ptl, packet);
ssh_packet_put(packet);
}
static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source)
{
struct ssh_frame *frame;
struct ssam_span payload;
struct ssam_span aligned;
bool syn_found;
int status;
/* Error injection: Modify data to simulate corrupt SYN bytes. */
ssh_ptl_rx_inject_invalid_syn(ptl, source);
/* Find SYN. */
syn_found = sshp_find_syn(source, &aligned);
if (unlikely(aligned.ptr != source->ptr)) {
/*
* We expect aligned.ptr == source->ptr. If this is not the
* case, then aligned.ptr > source->ptr and we've encountered
* some unexpected data where we'd expect the start of a new
* message (i.e. the SYN sequence).
*
* This can happen when a CRC check for the previous message
* failed and we start actively searching for the next one
* (via the call to sshp_find_syn() above), or the first bytes
* of a message got dropped or corrupted.
*
* In any case, we issue a warning, send a NAK to the EC to
* request re-transmission of any data we haven't acknowledged
* yet, and finally, skip everything up to the next SYN
* sequence.
*/
ptl_warn(ptl, "rx: parser: invalid start of frame, skipping\n");
/*
* Notes:
* - This might send multiple NAKs in case the communication
* starts with an invalid SYN and is broken down into multiple
* pieces. This should generally be handled fine, we just
* might receive duplicate data in this case, which is
* detected when handling data frames.
* - This path will also be executed on invalid CRCs: When an
* invalid CRC is encountered, the code below will skip data
* until directly after the SYN. This causes the search for
* the next SYN, which is generally not placed directly after
* the last one.
*
* Open question: Should we send this in case of invalid
* payload CRCs if the frame-type is non-sequential (current
* implementation) or should we drop that frame without
* telling the EC?
*/
ssh_ptl_send_nak(ptl);
}
if (unlikely(!syn_found))
return aligned.ptr - source->ptr;
/* Error injection: Modify data to simulate corruption. */
ssh_ptl_rx_inject_invalid_data(ptl, &aligned);
/* Parse and validate frame. */
status = sshp_parse_frame(&ptl->serdev->dev, &aligned, &frame, &payload,
SSH_PTL_RX_BUF_LEN);
if (status) /* Invalid frame: skip to next SYN. */
return aligned.ptr - source->ptr + sizeof(u16);
if (!frame) /* Not enough data. */
return aligned.ptr - source->ptr;
trace_ssam_rx_frame_received(frame);
switch (frame->type) {
case SSH_FRAME_TYPE_ACK:
ssh_ptl_acknowledge(ptl, frame->seq);
break;
case SSH_FRAME_TYPE_NAK:
ssh_ptl_resubmit_pending(ptl);
break;
case SSH_FRAME_TYPE_DATA_SEQ:
ssh_ptl_send_ack(ptl, frame->seq);
fallthrough;
case SSH_FRAME_TYPE_DATA_NSQ:
ssh_ptl_rx_dataframe(ptl, frame, &payload);
break;
default:
ptl_warn(ptl, "ptl: received frame with unknown type %#04x\n",
frame->type);
break;
}
return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(payload.len);
}
static int ssh_ptl_rx_threadfn(void *data)
{
struct ssh_ptl *ptl = data;
while (true) {
struct ssam_span span;
size_t offs = 0;
size_t n;
wait_event_interruptible(ptl->rx.wq,
!kfifo_is_empty(&ptl->rx.fifo) ||
kthread_should_stop());
if (kthread_should_stop())
break;
/* Copy from fifo to evaluation buffer. */
n = sshp_buf_read_from_fifo(&ptl->rx.buf, &ptl->rx.fifo);
ptl_dbg(ptl, "rx: received data (size: %zu)\n", n);
print_hex_dump_debug("rx: ", DUMP_PREFIX_OFFSET, 16, 1,
ptl->rx.buf.ptr + ptl->rx.buf.len - n,
n, false);
/* Parse until we need more bytes or buffer is empty. */
while (offs < ptl->rx.buf.len) {
sshp_buf_span_from(&ptl->rx.buf, offs, &span);
n = ssh_ptl_rx_eval(ptl, &span);
if (n == 0)
break; /* Need more bytes. */
offs += n;
}
/* Throw away the evaluated parts. */
sshp_buf_drop(&ptl->rx.buf, offs);
}
return 0;
}
static void ssh_ptl_rx_wakeup(struct ssh_ptl *ptl)
{
wake_up(&ptl->rx.wq);
}
/**
* ssh_ptl_rx_start() - Start packet transport layer receiver thread.
* @ptl: The packet transport layer.
*
* Return: Returns zero on success, a negative error code on failure.
*/
int ssh_ptl_rx_start(struct ssh_ptl *ptl)
{
if (ptl->rx.thread)
return 0;
ptl->rx.thread = kthread_run(ssh_ptl_rx_threadfn, ptl,
"ssam_serial_hub-rx");
if (IS_ERR(ptl->rx.thread))
return PTR_ERR(ptl->rx.thread);
return 0;
}
/**
* ssh_ptl_rx_stop() - Stop packet transport layer receiver thread.
* @ptl: The packet transport layer.
*
* Return: Returns zero on success, a negative error code on failure.
*/
int ssh_ptl_rx_stop(struct ssh_ptl *ptl)
{
int status = 0;
if (ptl->rx.thread) {
status = kthread_stop(ptl->rx.thread);
ptl->rx.thread = NULL;
}
return status;
}
/**
* ssh_ptl_rx_rcvbuf() - Push data from lower-layer transport to the packet
* layer.
* @ptl: The packet transport layer.
* @buf: Pointer to the data to push to the layer.
* @n: Size of the data to push to the layer, in bytes.
*
* Pushes data from a lower-layer transport to the receiver fifo buffer of the
* packet layer and notifies the receiver thread. Calls to this function are
* ignored once the packet layer has been shut down.
*
* Return: Returns the number of bytes transferred (positive or zero) on
* success. Returns %-ESHUTDOWN if the packet layer has been shut down.
*/
int ssh_ptl_rx_rcvbuf(struct ssh_ptl *ptl, const u8 *buf, size_t n)
{
int used;
if (test_bit(SSH_PTL_SF_SHUTDOWN_BIT, &ptl->state))
return -ESHUTDOWN;
used = kfifo_in(&ptl->rx.fifo, buf, n);
if (used)
ssh_ptl_rx_wakeup(ptl);
return used;
}
/**
* ssh_ptl_shutdown() - Shut down the packet transport layer.
* @ptl: The packet transport layer.
*
* Shuts down the packet transport layer, removing and canceling all queued
* and pending packets. Packets canceled by this operation will be completed
* with %-ESHUTDOWN as status. Receiver and transmitter threads will be
* stopped.
*
* As a result of this function, the transport layer will be marked as shut
* down. Submission of packets after the transport layer has been shut down
* will fail with %-ESHUTDOWN.
*/
void ssh_ptl_shutdown(struct ssh_ptl *ptl)
{
LIST_HEAD(complete_q);
LIST_HEAD(complete_p);
struct ssh_packet *p, *n;
int status;
/* Ensure that no new packets (including ACK/NAK) can be submitted. */
set_bit(SSH_PTL_SF_SHUTDOWN_BIT, &ptl->state);
/*
* Ensure that the layer gets marked as shut-down before actually
* stopping it. In combination with the check in ssh_ptl_queue_push(),
* this guarantees that no new packets can be added and all already
* queued packets are properly canceled. In combination with the check
* in ssh_ptl_rx_rcvbuf(), this guarantees that received data is
* properly cut off.
*/
smp_mb__after_atomic();
status = ssh_ptl_rx_stop(ptl);
if (status)
ptl_err(ptl, "ptl: failed to stop receiver thread\n");
status = ssh_ptl_tx_stop(ptl);
if (status)
ptl_err(ptl, "ptl: failed to stop transmitter thread\n");
cancel_delayed_work_sync(&ptl->rtx_timeout.reaper);
/*
* At this point, all threads have been stopped. This means that the
* only references to packets from inside the system are in the queue
* and pending set.
*
* Note: We still need locks here because someone could still be
* canceling packets.
*
* Note 2: We can re-use queue_node (or pending_node) if we mark the
* packet as locked an then remove it from the queue (or pending set
* respectively). Marking the packet as locked avoids re-queuing
* (which should already be prevented by having stopped the treads...)
* and not setting QUEUED_BIT (or PENDING_BIT) prevents removal from a
* new list via other threads (e.g. cancellation).
*
* Note 3: There may be overlap between complete_p and complete_q.
* This is handled via test_and_set_bit() on the "completed" flag
* (also handles cancellation).
*/
/* Mark queued packets as locked and move them to complete_q. */
spin_lock(&ptl->queue.lock);
list_for_each_entry_safe(p, n, &ptl->queue.head, queue_node) {
set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state);
/* Ensure that state does not get zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_QUEUED_BIT, &p->state);
list_del(&p->queue_node);
list_add_tail(&p->queue_node, &complete_q);
}
spin_unlock(&ptl->queue.lock);
/* Mark pending packets as locked and move them to complete_p. */
spin_lock(&ptl->pending.lock);
list_for_each_entry_safe(p, n, &ptl->pending.head, pending_node) {
set_bit(SSH_PACKET_SF_LOCKED_BIT, &p->state);
/* Ensure that state does not get zero. */
smp_mb__before_atomic();
clear_bit(SSH_PACKET_SF_PENDING_BIT, &p->state);
list_del(&p->pending_node);
list_add_tail(&p->pending_node, &complete_q);
}
atomic_set(&ptl->pending.count, 0);
spin_unlock(&ptl->pending.lock);
/* Complete and drop packets on complete_q. */
list_for_each_entry(p, &complete_q, queue_node) {
if (!test_and_set_bit(SSH_PACKET_SF_COMPLETED_BIT, &p->state))
__ssh_ptl_complete(p, -ESHUTDOWN);
ssh_packet_put(p);
}
/* Complete and drop packets on complete_p. */
list_for_each_entry(p, &complete_p, pending_node) {
if (!test_and_set_bit(SSH_PACKET_SF_COMPLETED_BIT, &p->state))
__ssh_ptl_complete(p, -ESHUTDOWN);
ssh_packet_put(p);
}
/*
* At this point we have guaranteed that the system doesn't reference
* any packets any more.
*/
}
/**
* ssh_ptl_init() - Initialize packet transport layer.
* @ptl: The packet transport layer to initialize.
* @serdev: The underlying serial device, i.e. the lower-level transport.
* @ops: Packet layer operations.
*
* Initializes the given packet transport layer. Transmitter and receiver
* threads must be started separately via ssh_ptl_tx_start() and
* ssh_ptl_rx_start(), after the packet-layer has been initialized and the
* lower-level transport layer has been set up.
*
* Return: Returns zero on success and a nonzero error code on failure.
*/
int ssh_ptl_init(struct ssh_ptl *ptl, struct serdev_device *serdev,
struct ssh_ptl_ops *ops)
{
int i, status;
ptl->serdev = serdev;
ptl->state = 0;
spin_lock_init(&ptl->queue.lock);
INIT_LIST_HEAD(&ptl->queue.head);
spin_lock_init(&ptl->pending.lock);
INIT_LIST_HEAD(&ptl->pending.head);
atomic_set_release(&ptl->pending.count, 0);
ptl->tx.thread = NULL;
atomic_set(&ptl->tx.running, 0);
init_completion(&ptl->tx.thread_cplt_pkt);
init_completion(&ptl->tx.thread_cplt_tx);
init_waitqueue_head(&ptl->tx.packet_wq);
ptl->rx.thread = NULL;
init_waitqueue_head(&ptl->rx.wq);
spin_lock_init(&ptl->rtx_timeout.lock);
ptl->rtx_timeout.timeout = SSH_PTL_PACKET_TIMEOUT;
ptl->rtx_timeout.expires = KTIME_MAX;
INIT_DELAYED_WORK(&ptl->rtx_timeout.reaper, ssh_ptl_timeout_reap);
ptl->ops = *ops;
/* Initialize list of recent/blocked SEQs with invalid sequence IDs. */
for (i = 0; i < ARRAY_SIZE(ptl->rx.blocked.seqs); i++)
ptl->rx.blocked.seqs[i] = U16_MAX;
ptl->rx.blocked.offset = 0;
status = kfifo_alloc(&ptl->rx.fifo, SSH_PTL_RX_FIFO_LEN, GFP_KERNEL);
if (status)
return status;
status = sshp_buf_alloc(&ptl->rx.buf, SSH_PTL_RX_BUF_LEN, GFP_KERNEL);
if (status)
kfifo_free(&ptl->rx.fifo);
return status;
}
/**
* ssh_ptl_destroy() - Deinitialize packet transport layer.
* @ptl: The packet transport layer to deinitialize.
*
* Deinitializes the given packet transport layer and frees resources
* associated with it. If receiver and/or transmitter threads have been
* started, the layer must first be shut down via ssh_ptl_shutdown() before
* this function can be called.
*/
void ssh_ptl_destroy(struct ssh_ptl *ptl)
{
kfifo_free(&ptl->rx.fifo);
sshp_buf_free(&ptl->rx.buf);
}
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