diff options
| author | Cristian Marussi <cristian.marussi@arm.com> | 2022-10-28 17:08:28 +0300 |
|---|---|---|
| committer | Sudeep Holla <sudeep.holla@arm.com> | 2022-11-01 14:33:24 +0300 |
| commit | 59172b212ec0dbb97ceb5671d912e6e61fa802d5 (patch) | |
| tree | 4b4d06b583c20fe992f388835a5b6e21acb4efaf /drivers/firmware/arm_scmi/shmem.c | |
| parent | fd96fbc8fad35d6b1872c90df8a2f5d721f14d91 (diff) | |
| download | linux-59172b212ec0dbb97ceb5671d912e6e61fa802d5.tar.xz | |
firmware: arm_scmi: Make tx_prepare time out eventually
SCMI transports based on shared memory, at start of transmissions, have
to wait for the shared Tx channel area to be eventually freed by the
SCMI platform before accessing the channel. In fact the channel is owned
by the SCMI platform until marked as free by the platform itself and,
as such, cannot be used by the agent until relinquished.
As a consequence a badly misbehaving SCMI platform firmware could lock
the channel indefinitely and make the kernel side SCMI stack loop
forever waiting for such channel to be freed, possibly hanging the
whole boot sequence.
Add a timeout to the existent Tx waiting spin-loop so that, when the
system ends up in this situation, the SCMI stack can at least bail-out,
nosily warn the user, and abort the transmission.
Reported-by: YaxiongTian <iambestgod@outlook.com>
Suggested-by: YaxiongTian <iambestgod@outlook.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221028140833.280091-3-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Diffstat (limited to 'drivers/firmware/arm_scmi/shmem.c')
| -rw-r--r-- | drivers/firmware/arm_scmi/shmem.c | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c index 0e3eaea5d852..1dfe534b8518 100644 --- a/drivers/firmware/arm_scmi/shmem.c +++ b/drivers/firmware/arm_scmi/shmem.c @@ -5,10 +5,13 @@ * Copyright (C) 2019 ARM Ltd. */ +#include <linux/ktime.h> #include <linux/io.h> #include <linux/processor.h> #include <linux/types.h> +#include <asm-generic/bug.h> + #include "common.h" /* @@ -30,16 +33,36 @@ struct scmi_shared_mem { }; void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem, - struct scmi_xfer *xfer) + struct scmi_xfer *xfer, struct scmi_chan_info *cinfo) { + ktime_t stop; + /* * Ideally channel must be free by now unless OS timeout last * request and platform continued to process the same, wait * until it releases the shared memory, otherwise we may endup - * overwriting its response with new message payload or vice-versa + * overwriting its response with new message payload or vice-versa. + * Giving up anyway after twice the expected channel timeout so as + * not to bail-out on intermittent issues where the platform is + * occasionally a bit slower to answer. + * + * Note that after a timeout is detected we bail-out and carry on but + * the transport functionality is probably permanently compromised: + * this is just to ease debugging and avoid complete hangs on boot + * due to a misbehaving SCMI firmware. */ - spin_until_cond(ioread32(&shmem->channel_status) & - SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE); + stop = ktime_add_ms(ktime_get(), 2 * cinfo->rx_timeout_ms); + spin_until_cond((ioread32(&shmem->channel_status) & + SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE) || + ktime_after(ktime_get(), stop)); + if (!(ioread32(&shmem->channel_status) & + SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE)) { + WARN_ON_ONCE(1); + dev_err(cinfo->dev, + "Timeout waiting for a free TX channel !\n"); + return; + } + /* Mark channel busy + clear error */ iowrite32(0x0, &shmem->channel_status); iowrite32(xfer->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED, |