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From:   Daniel Vetter <daniel@ffwll.ch>
Date:   Thu, 5 Apr 2018 15:29:44 +0200
Message-ID: <CAKMK7uGF81MDaCwxw+UKUUUGCLRqVzDdDQpMsJr2BC=4b7_5gA@mail.gmail.com>
Subject: Re: [PATCH] drm/sched: Extend the documentation.
To:     Alex Deucher <alexdeucher@gmail.com>
Cc:     Eric Anholt <eric@anholt.net>,
        Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Apr 5, 2018 at 3:27 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
> On Thu, Apr 5, 2018 at 2:16 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
>> On Thu, Apr 5, 2018 at 12:32 AM, Eric Anholt <eric@anholt.net> wrote:
>>> These comments answer all the questions I had for myself when
>>> implementing a driver using the GPU scheduler.
>>>
>>> Signed-off-by: Eric Anholt <eric@anholt.net>
>>
>> Pulling all these comments into the generated kerneldoc would be
>> awesome, maybe as a new "GPU Scheduler" chapter at the end of
>> drm-mm.rst? Would mean a bit of busywork to convert the existing raw
>> comments into proper kerneldoc. Also has the benefit that 0day will
>> complain when you forget to update the comment when editing the
>> function prototype - kerneldoc which isn't included anywhere in .rst
>> won't be checked automatically.
>
> I was actually planning to do this myself, but Nayan wanted to do this
> a prep work for his proposed GSoC project so I was going to see how
> far he got first.

Awesome. I'm also happy to help out with any kerneldoc questions and
best practices. Technically ofc no clue about the scheduler :-)

Cheers, Daniel
> Alex
>
>> -Daniel
>>
>>> ---
>>>  include/drm/gpu_scheduler.h | 46 +++++++++++++++++++++++++++++++++----
>>>  1 file changed, 42 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>>> index dfd54fb94e10..c053a32341bf 100644
>>> --- a/include/drm/gpu_scheduler.h
>>> +++ b/include/drm/gpu_scheduler.h
>>> @@ -43,10 +43,12 @@ enum drm_sched_priority {
>>>  };
>>>
>>>  /**
>>> - * A scheduler entity is a wrapper around a job queue or a group
>>> - * of other entities. Entities take turns emitting jobs from their
>>> - * job queues to corresponding hardware ring based on scheduling
>>> - * policy.
>>> + * drm_sched_entity - A wrapper around a job queue (typically attached
>>> + * to the DRM file_priv).
>>> + *
>>> + * Entities will emit jobs in order to their corresponding hardware
>>> + * ring, and the scheduler will alternate between entities based on
>>> + * scheduling policy.
>>>  */
>>>  struct drm_sched_entity {
>>>         struct list_head                list;
>>> @@ -78,7 +80,18 @@ struct drm_sched_rq {
>>>
>>>  struct drm_sched_fence {
>>>         struct dma_fence                scheduled;
>>> +
>>> +       /* This fence is what will be signaled by the scheduler when
>>> +        * the job is completed.
>>> +        *
>>> +        * When setting up an out fence for the job, you should use
>>> +        * this, since it's available immediately upon
>>> +        * drm_sched_job_init(), and the fence returned by the driver
>>> +        * from run_job() won't be created until the dependencies have
>>> +        * resolved.
>>> +        */
>>>         struct dma_fence                finished;
>>> +
>>>         struct dma_fence_cb             cb;
>>>         struct dma_fence                *parent;
>>>         struct drm_gpu_scheduler        *sched;
>>> @@ -88,6 +101,13 @@ struct drm_sched_fence {
>>>
>>>  struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>>>
>>> +/**
>>> + * drm_sched_job - A job to be run by an entity.
>>> + *
>>> + * A job is created by the driver using drm_sched_job_init(), and
>>> + * should call drm_sched_entity_push_job() once it wants the scheduler
>>> + * to schedule the job.
>>> + */
>>>  struct drm_sched_job {
>>>         struct spsc_node                queue_node;
>>>         struct drm_gpu_scheduler        *sched;
>>> @@ -112,10 +132,28 @@ static inline bool drm_sched_invalidate_job(struct drm_sched_job *s_job,
>>>   * these functions should be implemented in driver side
>>>  */
>>>  struct drm_sched_backend_ops {
>>> +       /* Called when the scheduler is considering scheduling this
>>> +        * job next, to get another struct dma_fence for this job to
>>> +        * block on.  Once it returns NULL, run_job() may be called.
>>> +        */
>>>         struct dma_fence *(*dependency)(struct drm_sched_job *sched_job,
>>>                                         struct drm_sched_entity *s_entity);
>>> +
>>> +       /* Called to execute the job once all of the dependencies have
>>> +        * been resolved.  This may be called multiple times, if
>>> +        * timedout_job() has happened and drm_sched_job_recovery()
>>> +        * decides to try it again.
>>> +        */
>>>         struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
>>> +
>>> +       /* Called when a job has taken too long to execute, to trigger
>>> +        * GPU recovery.
>>> +        */
>>>         void (*timedout_job)(struct drm_sched_job *sched_job);
>>> +
>>> +       /* Called once the job's finished fence has been signaled and
>>> +        * it's time to clean it up.
>>> +        */
>>>         void (*free_job)(struct drm_sched_job *sched_job);
>>>  };
>>>
>>> --
>>> 2.17.0
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>>
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch