linux-kernel - Re: [PATCH v2] drm/panfrost: Sync IRQ by job's timeout handler

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Date:   Mon, 24 Jul 2023 09:51:02 +0100
From:   Steven Price <steven.price@....com>
To:     Boris Brezillon <boris.brezillon@...labora.com>,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     Rob Herring <robh@...nel.org>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v2] drm/panfrost: Sync IRQ by job's timeout handler

On 24/07/2023 07:57, Boris Brezillon wrote:
> On Sun, 23 Jul 2023 03:01:42 +0300
> Dmitry Osipenko <dmitry.osipenko@...labora.com> wrote:
> 
>> Panfrost IRQ handler may stuck for a long time, for example this happens
>> when there is a bad HDMI connection and HDMI handler takes a long time to
>> finish processing, holding Panfrost. Make Panfrost's job timeout handler
>> to sync IRQ before checking fence signal status in order to prevent
>> spurious job timeouts due to a slow IRQ processing.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
>> ---
>>
>> Changelog:
>>
>> v2: - Moved synchronize_irq() after first signal-check to avoid unnecessary
>>       blocking on syncing.
>>
>>     - Added warn message about high interrupt latency.
>>
>>  drivers/gpu/drm/panfrost/panfrost_job.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
>> index dbc597ab46fb..a7663d7847a2 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
>> @@ -720,6 +720,13 @@ static enum drm_gpu_sched_stat panfrost_job_timedout(struct drm_sched_job
>>  	if (dma_fence_is_signaled(job->done_fence))
>>  		return DRM_GPU_SCHED_STAT_NOMINAL;
>>  
>> +	synchronize_irq(pfdev->js->irq);
> 
> Can we add a comment here explaining why we're doing that?

Agreed, with a comment added:

Reviewed-by: Steven Price <steven.price@....com>

>> +
>> +	if (dma_fence_is_signaled(job->done_fence)) {
>> +		dev_warn(pfdev->dev, "unexpectedly high interrupt latency\n");
>> +		return DRM_GPU_SCHED_STAT_NOMINAL;
>> +	}
>> +
>>  	dev_err(pfdev->dev, "gpu sched timeout, js=%d, config=0x%x, status=0x%x, head=0x%x, tail=0x%x, sched_job=%p",
>>  		js,
>>  		job_read(pfdev, JS_CONFIG(js)),
>