linux-kernel - Re: [PATCH 7/7] drm/lima: Use the drm_gem_fence_array

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Message-ID: <87o95o4a78.fsf@anholt.net>
Date:   Tue, 02 Apr 2019 09:56:59 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Qiang Yu <yuq825@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        david.emett@...adcom.com, thomas.spurden@...adcom.com,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH 7/7] drm/lima: Use the drm_gem_fence_array_add helpers for our deps.

Qiang Yu <yuq825@...il.com> writes:

> On Tue, Apr 2, 2019 at 6:26 AM Eric Anholt <eric@...olt.net> wrote:
>>
>> I haven't tested this, but it's a pretty direct port of what I did for
>> v3d.
>>
>> Signed-off-by: Eric Anholt <eric@...olt.net>
>> ---
>>  drivers/gpu/drm/lima/lima_gem.c   | 37 +----------------
>>  drivers/gpu/drm/lima/lima_sched.c | 66 ++++++-------------------------
>>  drivers/gpu/drm/lima/lima_sched.h |  6 +--
>>  3 files changed, 16 insertions(+), 93 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
>> index 2d3cf96f6c58..8f80286c80b4 100644
>> --- a/drivers/gpu/drm/lima/lima_gem.c
>> +++ b/drivers/gpu/drm/lima/lima_gem.c
>> @@ -144,40 +144,7 @@ static int lima_gem_sync_bo(struct lima_sched_task *task, struct lima_bo *bo,
>>         if (explicit)
>>                 return 0;
>>
>> -       /* implicit sync use bo fence in resv obj */
>> -       if (write) {
>> -               unsigned nr_fences;
>> -               struct dma_fence **fences;
>> -               int i;
>> -
>> -               err = reservation_object_get_fences_rcu(
>> -                       bo->gem.resv, NULL, &nr_fences, &fences);
>> -               if (err || !nr_fences)
>> -                       return err;
>> -
>> -               for (i = 0; i < nr_fences; i++) {
>> -                       err = lima_sched_task_add_dep(task, fences[i]);
>> -                       if (err)
>> -                               break;
>> -               }
>> -
>> -               /* for error case free remaining fences */
>> -               for ( ; i < nr_fences; i++)
>> -                       dma_fence_put(fences[i]);
>> -
>> -               kfree(fences);
>> -       } else {
>> -               struct dma_fence *fence;
>> -
>> -               fence = reservation_object_get_excl_rcu(bo->gem.resv);
>> -               if (fence) {
>> -                       err = lima_sched_task_add_dep(task, fence);
>> -                       if (err)
>> -                               dma_fence_put(fence);
>> -               }
>> -       }
>> -
>> -       return err;
>> +       return drm_gem_fence_array_add_implicit(&task->deps, &bo->gem, write);
>>  }
>>
>>  static int lima_gem_lock_bos(struct lima_bo **bos, u32 nr_bos,
>> @@ -250,7 +217,7 @@ static int lima_gem_add_deps(struct drm_file *file, struct lima_submit *submit)
>>                 if (err)
>>                         return err;
>>
>> -               err = lima_sched_task_add_dep(submit->task, fence);
>> +               err = drm_gem_fence_array_add(&submit->task->deps, fence);
>>                 if (err) {
>>                         dma_fence_put(fence);
>>                         return err;
>> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
>> index 97bd9c1deb87..e253d031fb3d 100644
>> --- a/drivers/gpu/drm/lima/lima_sched.c
>> +++ b/drivers/gpu/drm/lima/lima_sched.c
>> @@ -3,6 +3,7 @@
>>
>>  #include <linux/kthread.h>
>>  #include <linux/slab.h>
>> +#include <linux/xarray.h>
>>
>>  #include "lima_drv.h"
>>  #include "lima_sched.h"
>> @@ -126,19 +127,24 @@ int lima_sched_task_init(struct lima_sched_task *task,
>>
>>         task->num_bos = num_bos;
>>         task->vm = lima_vm_get(vm);
>> +
>> +       xa_init_flags(&task->deps, XA_FLAGS_ALLOC);
>> +
>>         return 0;
>>  }
>>
>>  void lima_sched_task_fini(struct lima_sched_task *task)
>>  {
>> +       struct dma_fence *fence;
>> +       unsigned long index;
>>         int i;
>>
>>         drm_sched_job_cleanup(&task->base);
>>
>> -       for (i = 0; i < task->num_dep; i++)
>> -               dma_fence_put(task->dep[i]);
>> -
>> -       kfree(task->dep);
>> +       xa_for_each(&task->deps, index, fence) {
>> +               dma_fence_put(fence);
>> +       }
>> +       xa_destroy(&task->deps);
>>
>>         if (task->bos) {
>>                 for (i = 0; i < task->num_bos; i++)
>> @@ -149,42 +155,6 @@ void lima_sched_task_fini(struct lima_sched_task *task)
>>         lima_vm_put(task->vm);
>>  }
>>
>> -int lima_sched_task_add_dep(struct lima_sched_task *task, struct dma_fence *fence)
>> -{
>> -       int i, new_dep = 4;
>> -
>> -       /* same context's fence is definitly earlier then this task */
>> -       if (fence->context == task->base.s_fence->finished.context) {
>> -               dma_fence_put(fence);
>> -               return 0;
>> -       }
>
> Seems you dropped this check in the drm_gem_fence_array_add, no bug if we
> don't have this, but redundant fence will be added in the deps array. Maybe we
> can add a context parameter to drm_gem_fence_array_add and
> drm_gem_fence_array_add_implicit to filter out fences from same
> drm_sched_entity.

Does this feel important to you?  To me, one extra slot in the array and
a trip through the top of drm_sched_entity_add_dependency_cb() doesn't
like it's feel worth making the API clumsier.

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