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From:   Nayan Deshmukh <nayan26deshmukh@gmail.com>
Date:   Thu, 5 Apr 2018 19:11:58 +0530
Message-ID: <CAFd4ddyMvoWObq1728aE8r8MrQNEKsEuxGV+DJMhGH+8EtDaZQ@mail.gmail.com>
Subject: Re: [PATCH] drm/sched: Extend the documentation.
To:     Daniel Vetter <daniel@ffwll.ch>
Cc:     Alex Deucher <alexdeucher@gmail.com>,
        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 6:59 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> 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.

It is still on my TODO list. Just got a bit busy with my coursework. I
will try to look at it during the weekend.
>
> Awesome. I'm also happy to help out with any kerneldoc questions and
> best practices. Technically ofc no clue about the scheduler :-)
>
I was thinking of adding a different rst for scheduler altogther. Will
it be better to add it in drm-mm.rst itself?

> 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
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel