/*
 * Copyright (C) 2013, 2014 ARM Limited, All Rights Reserved.
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/bitmap.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/log2.h>
#include <linux/mm.h>
#include <linux/msi.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_pci.h>
#include <linux/of_platform.h>
#include <linux/percpu.h>
#include <linux/slab.h>

#include <linux/irqchip/arm-gic-v3.h>

#include <asm/cacheflush.h>
#include <asm/cputype.h>
#include <asm/exception.h>

#include "irqchip.h"

#define ITS_FLAGS_CMDQ_NEEDS_FLUSHING		(1 << 0)

#define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING	(1 << 0)

/*
 * Collection structure - just an ID, and a redistributor address to
 * ping. We use one per CPU as a bag of interrupts assigned to this
 * CPU.
 */
struct its_collection {
	u64			target_address;
	u16			col_id;
};

/*
 * The ITS structure - contains most of the infrastructure, with the
 * msi_controller, the command queue, the collections, and the list of
 * devices writing to it.
 */
struct its_node {
	raw_spinlock_t		lock;
	struct list_head	entry;
	struct msi_controller	msi_chip;
	struct irq_domain	*domain;
	void __iomem		*base;
	unsigned long		phys_base;
	struct its_cmd_block	*cmd_base;
	struct its_cmd_block	*cmd_write;
	void			*tables[GITS_BASER_NR_REGS];
	struct its_collection	*collections;
	struct list_head	its_device_list;
	u64			flags;
	u32			ite_size;
};

#define ITS_ITT_ALIGN		SZ_256

/*
 * The ITS view of a device - belongs to an ITS, a collection, owns an
 * interrupt translation table, and a list of interrupts.
 */
struct its_device {
	struct list_head	entry;
	struct its_node		*its;
	struct its_collection	*collection;
	void			*itt;
	unsigned long		*lpi_map;
	irq_hw_number_t		lpi_base;
	int			nr_lpis;
	u32			nr_ites;
	u32			device_id;
};

/*
 * ITS command descriptors - parameters to be encoded in a command
 * block.
 */
struct its_cmd_desc {
	union {
		struct {
			struct its_device *dev;
			u32 event_id;
		} its_inv_cmd;

		struct {
			struct its_device *dev;
			u32 event_id;
		} its_int_cmd;

		struct {
			struct its_device *dev;
			int valid;
		} its_mapd_cmd;

		struct {
			struct its_collection *col;
			int valid;
		} its_mapc_cmd;

		struct {
			struct its_device *dev;
			u32 phys_id;
			u32 event_id;
		} its_mapvi_cmd;

		struct {
			struct its_device *dev;
			struct its_collection *col;
			u32 id;
		} its_movi_cmd;

		struct {
			struct its_device *dev;
			u32 event_id;
		} its_discard_cmd;

		struct {
			struct its_collection *col;
		} its_invall_cmd;
	};
};

/*
 * The ITS command block, which is what the ITS actually parses.
 */
struct its_cmd_block {
	u64	raw_cmd[4];
};

#define ITS_CMD_QUEUE_SZ		SZ_64K
#define ITS_CMD_QUEUE_NR_ENTRIES	(ITS_CMD_QUEUE_SZ / sizeof(struct its_cmd_block))

typedef struct its_collection *(*its_cmd_builder_t)(struct its_cmd_block *,
						    struct its_cmd_desc *);

static void its_encode_cmd(struct its_cmd_block *cmd, u8 cmd_nr)
{
	cmd->raw_cmd[0] &= ~0xffUL;
	cmd->raw_cmd[0] |= cmd_nr;
}

static void its_encode_devid(struct its_cmd_block *cmd, u32 devid)
{
	cmd->raw_cmd[0] &= ~(0xffffUL << 32);
	cmd->raw_cmd[0] |= ((u64)devid) << 32;
}

static void its_encode_event_id(struct its_cmd_block *cmd, u32 id)
{
	cmd->raw_cmd[1] &= ~0xffffffffUL;
	cmd->raw_cmd[1] |= id;
}

static void its_encode_phys_id(struct its_cmd_block *cmd, u32 phys_id)
{
	cmd->raw_cmd[1] &= 0xffffffffUL;
	cmd->raw_cmd[1] |= ((u64)phys_id) << 32;
}

static void its_encode_size(struct its_cmd_block *cmd, u8 size)
{
	cmd->raw_cmd[1] &= ~0x1fUL;
	cmd->raw_cmd[1] |= size & 0x1f;
}

static void its_encode_itt(struct its_cmd_block *cmd, u64 itt_addr)
{
	cmd->raw_cmd[2] &= ~0xffffffffffffUL;
	cmd->raw_cmd[2] |= itt_addr & 0xffffffffff00UL;
}

static void its_encode_valid(struct its_cmd_block *cmd, int valid)
{
	cmd->raw_cmd[2] &= ~(1UL << 63);
	cmd->raw_cmd[2] |= ((u64)!!valid) << 63;
}

static void its_encode_target(struct its_cmd_block *cmd, u64 target_addr)
{
	cmd->raw_cmd[2] &= ~(0xffffffffUL << 16);
	cmd->raw_cmd[2] |= (target_addr & (0xffffffffUL << 16));
}

static void its_encode_collection(struct its_cmd_block *cmd, u16 col)
{
	cmd->raw_cmd[2] &= ~0xffffUL;
	cmd->raw_cmd[2] |= col;
}

static inline void its_fixup_cmd(struct its_cmd_block *cmd)
{
	/* Let's fixup BE commands */
	cmd->raw_cmd[0] = cpu_to_le64(cmd->raw_cmd[0]);
	cmd->raw_cmd[1] = cpu_to_le64(cmd->raw_cmd[1]);
	cmd->raw_cmd[2] = cpu_to_le64(cmd->raw_cmd[2]);
	cmd->raw_cmd[3] = cpu_to_le64(cmd->raw_cmd[3]);
}

static struct its_collection *its_build_mapd_cmd(struct its_cmd_block *cmd,
						 struct its_cmd_desc *desc)
{
	unsigned long itt_addr;
	u8 size = order_base_2(desc->its_mapd_cmd.dev->nr_ites);

	itt_addr = virt_to_phys(desc->its_mapd_cmd.dev->itt);
	itt_addr = ALIGN(itt_addr, ITS_ITT_ALIGN);

	its_encode_cmd(cmd, GITS_CMD_MAPD);
	its_encode_devid(cmd, desc->its_mapd_cmd.dev->device_id);
	its_encode_size(cmd, size - 1);
	its_encode_itt(cmd, itt_addr);
	its_encode_valid(cmd, desc->its_mapd_cmd.valid);

	its_fixup_cmd(cmd);

	return desc->its_mapd_cmd.dev->collection;
}

static struct its_collection *its_build_mapc_cmd(struct its_cmd_block *cmd,
						 struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_MAPC);
	its_encode_collection(cmd, desc->its_mapc_cmd.col->col_id);
	its_encode_target(cmd, desc->its_mapc_cmd.col->target_address);
	its_encode_valid(cmd, desc->its_mapc_cmd.valid);

	its_fixup_cmd(cmd);

	return desc->its_mapc_cmd.col;
}

static struct its_collection *its_build_mapvi_cmd(struct its_cmd_block *cmd,
						  struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_MAPVI);
	its_encode_devid(cmd, desc->its_mapvi_cmd.dev->device_id);
	its_encode_event_id(cmd, desc->its_mapvi_cmd.event_id);
	its_encode_phys_id(cmd, desc->its_mapvi_cmd.phys_id);
	its_encode_collection(cmd, desc->its_mapvi_cmd.dev->collection->col_id);

	its_fixup_cmd(cmd);

	return desc->its_mapvi_cmd.dev->collection;
}

static struct its_collection *its_build_movi_cmd(struct its_cmd_block *cmd,
						 struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_MOVI);
	its_encode_devid(cmd, desc->its_movi_cmd.dev->device_id);
	its_encode_event_id(cmd, desc->its_movi_cmd.id);
	its_encode_collection(cmd, desc->its_movi_cmd.col->col_id);

	its_fixup_cmd(cmd);

	return desc->its_movi_cmd.dev->collection;
}

static struct its_collection *its_build_discard_cmd(struct its_cmd_block *cmd,
						    struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_DISCARD);
	its_encode_devid(cmd, desc->its_discard_cmd.dev->device_id);
	its_encode_event_id(cmd, desc->its_discard_cmd.event_id);

	its_fixup_cmd(cmd);

	return desc->its_discard_cmd.dev->collection;
}

static struct its_collection *its_build_inv_cmd(struct its_cmd_block *cmd,
						struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_INV);
	its_encode_devid(cmd, desc->its_inv_cmd.dev->device_id);
	its_encode_event_id(cmd, desc->its_inv_cmd.event_id);

	its_fixup_cmd(cmd);

	return desc->its_inv_cmd.dev->collection;
}

static struct its_collection *its_build_invall_cmd(struct its_cmd_block *cmd,
						   struct its_cmd_desc *desc)
{
	its_encode_cmd(cmd, GITS_CMD_INVALL);
	its_encode_collection(cmd, desc->its_mapc_cmd.col->col_id);

	its_fixup_cmd(cmd);

	return NULL;
}

static u64 its_cmd_ptr_to_offset(struct its_node *its,
				 struct its_cmd_block *ptr)
{
	return (ptr - its->cmd_base) * sizeof(*ptr);
}

static int its_queue_full(struct its_node *its)
{
	int widx;
	int ridx;

	widx = its->cmd_write - its->cmd_base;
	ridx = readl_relaxed(its->base + GITS_CREADR) / sizeof(struct its_cmd_block);

	/* This is incredibly unlikely to happen, unless the ITS locks up. */
	if (((widx + 1) % ITS_CMD_QUEUE_NR_ENTRIES) == ridx)
		return 1;

	return 0;
}

static struct its_cmd_block *its_allocate_entry(struct its_node *its)
{
	struct its_cmd_block *cmd;
	u32 count = 1000000;	/* 1s! */

	while (its_queue_full(its)) {
		count--;
		if (!count) {
			pr_err_ratelimited("ITS queue not draining\n");
			return NULL;
		}
		cpu_relax();
		udelay(1);
	}

	cmd = its->cmd_write++;

	/* Handle queue wrapping */
	if (its->cmd_write == (its->cmd_base + ITS_CMD_QUEUE_NR_ENTRIES))
		its->cmd_write = its->cmd_base;

	return cmd;
}

static struct its_cmd_block *its_post_commands(struct its_node *its)
{
	u64 wr = its_cmd_ptr_to_offset(its, its->cmd_write);

	writel_relaxed(wr, its->base + GITS_CWRITER);

	return its->cmd_write;
}

static void its_flush_cmd(struct its_node *its, struct its_cmd_block *cmd)
{
	/*
	 * Make sure the commands written to memory are observable by
	 * the ITS.
	 */
	if (its->flags & ITS_FLAGS_CMDQ_NEEDS_FLUSHING)
		__flush_dcache_area(cmd, sizeof(*cmd));
	else
		dsb(ishst);
}

static void its_wait_for_range_completion(struct its_node *its,
					  struct its_cmd_block *from,
					  struct its_cmd_block *to)
{
	u64 rd_idx, from_idx, to_idx;
	u32 count = 1000000;	/* 1s! */

	from_idx = its_cmd_ptr_to_offset(its, from);
	to_idx = its_cmd_ptr_to_offset(its, to);

	while (1) {
		rd_idx = readl_relaxed(its->base + GITS_CREADR);
		if (rd_idx >= to_idx || rd_idx < from_idx)
			break;

		count--;
		if (!count) {
			pr_err_ratelimited("ITS queue timeout\n");
			return;
		}
		cpu_relax();
		udelay(1);
	}
}

static void its_send_single_command(struct its_node *its,
				    its_cmd_builder_t builder,
				    struct its_cmd_desc *desc)
{
	struct its_cmd_block *cmd, *sync_cmd, *next_cmd;
	struct its_collection *sync_col;

	raw_spin_lock(&its->lock);

	cmd = its_allocate_entry(its);
	if (!cmd) {		/* We're soooooo screewed... */
		pr_err_ratelimited("ITS can't allocate, dropping command\n");
		raw_spin_unlock(&its->lock);
		return;
	}
	sync_col = builder(cmd, desc);
	its_flush_cmd(its, cmd);

	if (sync_col) {
		sync_cmd = its_allocate_entry(its);
		if (!sync_cmd) {
			pr_err_ratelimited("ITS can't SYNC, skipping\n");
			goto post;
		}
		its_encode_cmd(sync_cmd, GITS_CMD_SYNC);
		its_encode_target(sync_cmd, sync_col->target_address);
		its_fixup_cmd(sync_cmd);
		its_flush_cmd(its, sync_cmd);
	}

post:
	next_cmd = its_post_commands(its);
	raw_spin_unlock(&its->lock);

	its_wait_for_range_completion(its, cmd, next_cmd);
}

static void its_send_inv(struct its_device *dev, u32 event_id)
{
	struct its_cmd_desc desc;

	desc.its_inv_cmd.dev = dev;
	desc.its_inv_cmd.event_id = event_id;

	its_send_single_command(dev->its, its_build_inv_cmd, &desc);
}

static void its_send_mapd(struct its_device *dev, int valid)
{
	struct its_cmd_desc desc;

	desc.its_mapd_cmd.dev = dev;
	desc.its_mapd_cmd.valid = !!valid;

	its_send_single_command(dev->its, its_build_mapd_cmd, &desc);
}

static void its_send_mapc(struct its_node *its, struct its_collection *col,
			  int valid)
{
	struct its_cmd_desc desc;

	desc.its_mapc_cmd.col = col;
	desc.its_mapc_cmd.valid = !!valid;

	its_send_single_command(its, its_build_mapc_cmd, &desc);
}

static void its_send_mapvi(struct its_device *dev, u32 irq_id, u32 id)
{
	struct its_cmd_desc desc;

	desc.its_mapvi_cmd.dev = dev;
	desc.its_mapvi_cmd.phys_id = irq_id;
	desc.its_mapvi_cmd.event_id = id;

	its_send_single_command(dev->its, its_build_mapvi_cmd, &desc);
}

static void its_send_movi(struct its_device *dev,
			  struct its_collection *col, u32 id)
{
	struct its_cmd_desc desc;

	desc.its_movi_cmd.dev = dev;
	desc.its_movi_cmd.col = col;
	desc.its_movi_cmd.id = id;

	its_send_single_command(dev->its, its_build_movi_cmd, &desc);
}

static void its_send_discard(struct its_device *dev, u32 id)
{
	struct its_cmd_desc desc;

	desc.its_discard_cmd.dev = dev;
	desc.its_discard_cmd.event_id = id;

	its_send_single_command(dev->its, its_build_discard_cmd, &desc);
}

static void its_send_invall(struct its_node *its, struct its_collection *col)
{
	struct its_cmd_desc desc;

	desc.its_invall_cmd.col = col;

	its_send_single_command(its, its_build_invall_cmd, &desc);
}

/*
 * irqchip functions - assumes MSI, mostly.
 */

static inline u32 its_get_event_id(struct irq_data *d)
{
	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
	return d->hwirq - its_dev->lpi_base;
}

static void lpi_set_config(struct irq_data *d, bool enable)
{
	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
	irq_hw_number_t hwirq = d->hwirq;
	u32 id = its_get_event_id(d);
	u8 *cfg = page_address(gic_rdists->prop_page) + hwirq - 8192;

	if (enable)
		*cfg |= LPI_PROP_ENABLED;
	else
		*cfg &= ~LPI_PROP_ENABLED;

	/*
	 * Make the above write visible to the redistributors.
	 * And yes, we're flushing exactly: One. Single. Byte.
	 * Humpf...
	 */
	if (gic_rdists->flags & RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING)
		__flush_dcache_area(cfg, sizeof(*cfg));
	else
		dsb(ishst);
	its_send_inv(its_dev, id);
}

static void its_mask_irq(struct irq_data *d)
{
	lpi_set_config(d, false);
}

static void its_unmask_irq(struct irq_data *d)
{
	lpi_set_config(d, true);
}

static void its_eoi_irq(struct irq_data *d)
{
	gic_write_eoir(d->hwirq);
}

static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
			    bool force)
{
	unsigned int cpu = cpumask_any_and(mask_val, cpu_online_mask);
	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
	struct its_collection *target_col;
	u32 id = its_get_event_id(d);

	if (cpu >= nr_cpu_ids)
		return -EINVAL;

	target_col = &its_dev->its->collections[cpu];
	its_send_movi(its_dev, target_col, id);
	its_dev->collection = target_col;

	return IRQ_SET_MASK_OK_DONE;
}

static struct irq_chip its_irq_chip = {
	.name			= "ITS",
	.irq_mask		= its_mask_irq,
	.irq_unmask		= its_unmask_irq,
	.irq_eoi		= its_eoi_irq,
	.irq_set_affinity	= its_set_affinity,
};

/*
 * How we allocate LPIs:
 *
 * The GIC has id_bits bits for interrupt identifiers. From there, we
 * must subtract 8192 which are reserved for SGIs/PPIs/SPIs. Then, as
 * we allocate LPIs by chunks of 32, we can shift the whole thing by 5
 * bits to the right.
 *
 * This gives us (((1UL << id_bits) - 8192) >> 5) possible allocations.
 */
#define IRQS_PER_CHUNK_SHIFT	5
#define IRQS_PER_CHUNK		(1 << IRQS_PER_CHUNK_SHIFT)

static unsigned long *lpi_bitmap;
static u32 lpi_chunks;
static DEFINE_SPINLOCK(lpi_lock);

static int its_lpi_to_chunk(int lpi)
{
	return (lpi - 8192) >> IRQS_PER_CHUNK_SHIFT;
}

static int its_chunk_to_lpi(int chunk)
{
	return (chunk << IRQS_PER_CHUNK_SHIFT) + 8192;
}

static int its_lpi_init(u32 id_bits)
{
	lpi_chunks = its_lpi_to_chunk(1UL << id_bits);

	lpi_bitmap = kzalloc(BITS_TO_LONGS(lpi_chunks) * sizeof(long),
			     GFP_KERNEL);
	if (!lpi_bitmap) {
		lpi_chunks = 0;
		return -ENOMEM;
	}

	pr_info("ITS: Allocated %d chunks for LPIs\n", (int)lpi_chunks);
	return 0;
}

static unsigned long *its_lpi_alloc_chunks(int nr_irqs, int *base, int *nr_ids)
{
	unsigned long *bitmap = NULL;
	int chunk_id;
	int nr_chunks;
	int i;

	nr_chunks = DIV_ROUND_UP(nr_irqs, IRQS_PER_CHUNK);

	spin_lock(&lpi_lock);

	do {
		chunk_id = bitmap_find_next_zero_area(lpi_bitmap, lpi_chunks,
						      0, nr_chunks, 0);
		if (chunk_id < lpi_chunks)
			break;

		nr_chunks--;
	} while (nr_chunks > 0);

	if (!nr_chunks)
		goto out;

	bitmap = kzalloc(BITS_TO_LONGS(nr_chunks * IRQS_PER_CHUNK) * sizeof (long),
			 GFP_ATOMIC);
	if (!bitmap)
		goto out;

	for (i = 0; i < nr_chunks; i++)
		set_bit(chunk_id + i, lpi_bitmap);

	*base = its_chunk_to_lpi(chunk_id);
	*nr_ids = nr_chunks * IRQS_PER_CHUNK;

out:
	spin_unlock(&lpi_lock);

	return bitmap;
}

static void its_lpi_free(unsigned long *bitmap, int base, int nr_ids)
{
	int lpi;

	spin_lock(&lpi_lock);

	for (lpi = base; lpi < (base + nr_ids); lpi += IRQS_PER_CHUNK) {
		int chunk = its_lpi_to_chunk(lpi);
		BUG_ON(chunk > lpi_chunks);
		if (test_bit(chunk, lpi_bitmap)) {
			clear_bit(chunk, lpi_bitmap);
		} else {
			pr_err("Bad LPI chunk %d\n", chunk);
		}
	}

	spin_unlock(&lpi_lock);

	kfree(bitmap);
}