Re: [PATCH 1/8] drm/panfrost: Make panfrost_job_run() return an ERR_PTR() instead of NULL

[Steven Price <steven.price@arm.com>]

On 29/11/2019 14:31, Boris Brezillon wrote:
> On Fri, 29 Nov 2019 14:19:50 +0000
> Steven Price <steven.price@arm.com> wrote:
> 
>> On 29/11/2019 13:59, Boris Brezillon wrote:
>>> If we don't do that, dma_fence_set_error() complains (called from
>>> drm_sched_main()).
>>>
>>> Fixes: f3ba91228e8e ("drm/panfrost: Add initial panfrost driver")
>>> Cc: <stable@vger.kernel.org>
>>> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>  
>>
>> This might be worth doing, but actually it's not Panfrost that is broken
>> it's the callers, see [1] and [2]. So I don't think we want the
>> Fixes/stable tag.
> 
> Okay.
> 
>>
>> [1] https://patchwork.kernel.org/patch/11218399/
>> [2] https://patchwork.kernel.org/patch/11267073/
>>
>>> ---
>>>  drivers/gpu/drm/panfrost/panfrost_job.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
>>> index 21f34d44aac2..cdd9448fbbdd 100644
>>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
>>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
>>> @@ -328,13 +328,13 @@ static struct dma_fence *panfrost_job_run(struct drm_sched_job *sched_job)
>>>  	struct dma_fence *fence = NULL;
>>>  
>>>  	if (unlikely(job->base.s_fence->finished.error))
>>> -		return NULL;
>>> +		return ERR_PTR(job->base.s_fence->finished.error);
> 
> Hm, so we can keep the return NULL here if [1] is applied (the error
> is preserved), but I'm not sure it's clearer that way.
> 
>>>  
>>>  	pfdev->jobs[slot] = job;
>>>  
>>>  	fence = panfrost_fence_create(pfdev, slot);
>>>  	if (IS_ERR(fence))
>>> -		return NULL;
>>> +		return ERR_PTR(-ENOMEM);  
> 
> This one should be fixed though, otherwise the error is never updated,
> so I'm wondering if it doesn't deserve a Fixes tag in the end...

Good point, although this can't be back-ported before [3] (well unless
that commit is considered stable material too), so this is only really
relevant for v5.4. But worth fixing there.

[3] 167bf96014a0 ("drm/sched: Set error to s_fence if HW job submission
failed.")

Steve

>>
>> Why override the error from panfrost_fence_create? In this case we can just:
>>
>> 	return fence;
> 
> Indeed.
> 
>>
>> Steve
>>
>>>  
>>>  	if (job->done_fence)
>>>  		dma_fence_put(job->done_fence);
>>>   
>>
> 
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