[03/25] media: venus: Rework error fail recover logic

The Venus code has a sort of watchdog that attempts to recover
from IP errors, implemented as a delayed work job, which
calls venus_sys_error_handler().

Right now, it has several issues:

1. It assumes that PM runtime resume never fails

2. It internally runs two while() loops that also assume that
   PM runtime will never fail to go idle:

	while (pm_runtime_active(core->dev_dec) || pm_runtime_active(core->dev_enc))
		msleep(10);

...

	while (core->pmdomains[0] && pm_runtime_active(core->pmdomains[0]))
		usleep_range(1000, 1500);

3. It uses an OR to merge all return codes and then report to the user

4. If the hardware never recovers, it keeps running on every 10ms,
   flooding the syslog with 2 messages (so, up to 200 messages
   per second).

Rework the code, in order to prevent that, by:

1. check the return code from PM runtime resume;
2. don't let the while() loops run forever;
3. store the failed event;
4. use warn ratelimited when it fails to recover.

Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 drivers/media/platform/qcom/venus/core.c | 59 +++++++++++++++++++-----
 1 file changed, 47 insertions(+), 12 deletions(-)

On Wed, 5 May 2021 11:41:53 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> wrote:

> The Venus code has a sort of watchdog that attempts to recover
> from IP errors, implemented as a delayed work job, which
> calls venus_sys_error_handler().
> 
> Right now, it has several issues:
> 
> 1. It assumes that PM runtime resume never fails
> 
> 2. It internally runs two while() loops that also assume that
>    PM runtime will never fail to go idle:
> 
> 	while (pm_runtime_active(core->dev_dec) || pm_runtime_active(core->dev_enc))
> 		msleep(10);
> 
> ...
> 
> 	while (core->pmdomains[0] && pm_runtime_active(core->pmdomains[0]))
> 		usleep_range(1000, 1500);
> 
> 3. It uses an OR to merge all return codes and then report to the user
> 
> 4. If the hardware never recovers, it keeps running on every 10ms,
>    flooding the syslog with 2 messages (so, up to 200 messages
>    per second).
> 
> Rework the code, in order to prevent that, by:
> 
> 1. check the return code from PM runtime resume;
> 2. don't let the while() loops run forever;
> 3. store the failed event;
> 4. use warn ratelimited when it fails to recover.
> 
> Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions")
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Trivial comments inline, otherwise based on no knowledge at all of the
actual hardware, the fix looks sane.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/media/platform/qcom/venus/core.c | 59 +++++++++++++++++++-----
>  1 file changed, 47 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
> index 54bac7ec14c5..4d0482743c0a 100644
> --- a/drivers/media/platform/qcom/venus/core.c
> +++ b/drivers/media/platform/qcom/venus/core.c
> @@ -78,22 +78,32 @@ static const struct hfi_core_ops venus_core_ops = {
>  	.event_notify = venus_event_notify,
>  };
>  
> +#define RPM_WAIT_FOR_IDLE_MAX_ATTEMPTS 10
> +
>  static void venus_sys_error_handler(struct work_struct *work)
>  {
>  	struct venus_core *core =
>  			container_of(work, struct venus_core, work.work);
> -	int ret = 0;
> +	int ret, i, max_attempts = RPM_WAIT_FOR_IDLE_MAX_ATTEMPTS;
> +	bool failed = false;
> +	const char *err_msg = "";
>  
> -	pm_runtime_get_sync(core->dev);
> +	ret = pm_runtime_get_sync(core->dev);
> +	if (ret < 0) {
> +		err_msg = "resume runtime PM\n";

Will end up with two newlines I think as %s\n" later.

> +		max_attempts = 0;
> +		failed = true;
> +	}
>  
>  	hfi_core_deinit(core, true);
>  
> -	dev_warn(core->dev, "system error has occurred, starting recovery!\n");
> -
>  	mutex_lock(&core->lock);
>  
> -	while (pm_runtime_active(core->dev_dec) || pm_runtime_active(core->dev_enc))
> +	for (i = 0; i < max_attempts; i++) {
> +		if (!pm_runtime_active(core->dev_dec) && !pm_runtime_active(core->dev_enc))
> +			break;
>  		msleep(10);
> +	}
>  
>  	venus_shutdown(core);
>  
> @@ -101,31 +111,56 @@ static void venus_sys_error_handler(struct work_struct *work)
>  
>  	pm_runtime_put_sync(core->dev);
>  
> -	while (core->pmdomains[0] && pm_runtime_active(core->pmdomains[0]))
> +	for (i = 0; i < max_attempts; i++) {
> +		if (!core->pmdomains[0] || !pm_runtime_active(core->pmdomains[0]))
> +			break;
>  		usleep_range(1000, 1500);
> +	}
>  
>  	hfi_reinit(core);
>  
> -	pm_runtime_get_sync(core->dev);
> +	ret = pm_runtime_get_sync(core->dev);
> +	if (ret < 0) {
> +		err_msg = "resume runtime PM\n";
> +		max_attempts = 0;

This is after the last use of max_attempts, so no point in setting it to zero.

> +		failed = true;
> +	}
>  
> -	ret |= venus_boot(core);
> -	ret |= hfi_core_resume(core, true);
> +	ret = venus_boot(core);
> +	if (ret && !failed) {
> +		err_msg = "boot Venus\n";
> +		failed = true;
> +	}
> +
> +	ret = hfi_core_resume(core, true);
> +	if (ret && !failed) {
> +		err_msg = "resume HFI\n";
> +		failed = true;
> +	}
>  
>  	enable_irq(core->irq);
>  
>  	mutex_unlock(&core->lock);
>  
> -	ret |= hfi_core_init(core);
> +	ret = hfi_core_init(core);
> +	if (ret && !failed) {
> +		err_msg = "init HFI\n";
> +		failed = true;
> +	}
>  
>  	pm_runtime_put_sync(core->dev);
>  
> -	if (ret) {
> +	if (failed) {
>  		disable_irq_nosync(core->irq);
> -		dev_warn(core->dev, "recovery failed (%d)\n", ret);
> +		dev_warn_ratelimited(core->dev,
> +				     "System error has occurred, recovery failed to %s\n",
> +				     err_msg);
>  		schedule_delayed_work(&core->work, msecs_to_jiffies(10));
>  		return;
>  	}
>  
> +	dev_warn(core->dev, "system error has occurred (recovered)\n");
> +
>  	mutex_lock(&core->lock);
>  	core->sys_error = false;
>  	mutex_unlock(&core->lock);