[PATCH 2/3] drm/amdgpu: Implement new dummy vram manager

[Felix Kuehling]

Am 2023-06-14 um 06:38 schrieb Christian König:
> Am 10.05.23 um 00:01 schrieb Alex Deucher:
>> From: Rajneesh Bhardwaj <rajneesh.bhardwaj at amd.com>
>>
>> This adds dummy vram manager to support ASICs that do not have a
>> dedicated or carvedout vram domain.
>
> Well that doesn't seem to make much sense. Why we should have that?

TTM always expects a resource manager for VRAM. There are no NULL 
pointer checks in TTM for not having a resource manager for VRAM. The 
existing amdgpu_vram_mgr gets confused if there is no VRAM. It seemed 
cleaner to add a dummy manager than to scatter conditions for a 
memory-less GPU corner case through the regular VRAM manager.

Regards,
   Felix


>
> Christian.
>
>>
>> Reviewed-by: Felix Kuehling <felix.kuehling at amd.com>
>> Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj at amd.com>
>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 67 ++++++++++++++++++--
>>   1 file changed, 60 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> index 43d6a9d6a538..89d35d194f2c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> @@ -370,6 +370,45 @@ int amdgpu_vram_mgr_query_page_status(struct 
>> amdgpu_vram_mgr *mgr,
>>       return ret;
>>   }
>>   +static void amdgpu_dummy_vram_mgr_debug(struct 
>> ttm_resource_manager *man,
>> +                  struct drm_printer *printer)
>> +{
>> +    DRM_DEBUG_DRIVER("Dummy vram mgr debug\n");
>> +}
>> +
>> +static bool amdgpu_dummy_vram_mgr_compatible(struct 
>> ttm_resource_manager *man,
>> +                       struct ttm_resource *res,
>> +                       const struct ttm_place *place,
>> +                       size_t size)
>> +{
>> +    DRM_DEBUG_DRIVER("Dummy vram mgr compatible\n");
>> +    return false;
>> +}
>> +
>> +static bool amdgpu_dummy_vram_mgr_intersects(struct 
>> ttm_resource_manager *man,
>> +                       struct ttm_resource *res,
>> +                       const struct ttm_place *place,
>> +                       size_t size)
>> +{
>> +    DRM_DEBUG_DRIVER("Dummy vram mgr intersects\n");
>> +    return true;
>> +}
>> +
>> +static void amdgpu_dummy_vram_mgr_del(struct ttm_resource_manager *man,
>> +                struct ttm_resource *res)
>> +{
>> +    DRM_DEBUG_DRIVER("Dummy vram mgr deleted\n");
>> +}
>> +
>> +static int amdgpu_dummy_vram_mgr_new(struct ttm_resource_manager *man,
>> +                   struct ttm_buffer_object *tbo,
>> +                   const struct ttm_place *place,
>> +                   struct ttm_resource **res)
>> +{
>> +    DRM_DEBUG_DRIVER("Dummy vram mgr new\n");
>> +    return -ENOSPC;
>> +}
>> +
>>   /**
>>    * amdgpu_vram_mgr_new - allocate new ranges
>>    *
>> @@ -817,6 +856,14 @@ static void amdgpu_vram_mgr_debug(struct 
>> ttm_resource_manager *man,
>>       mutex_unlock(&mgr->lock);
>>   }
>>   +static const struct ttm_resource_manager_func 
>> amdgpu_dummy_vram_mgr_func = {
>> +    .alloc    = amdgpu_dummy_vram_mgr_new,
>> +    .free    = amdgpu_dummy_vram_mgr_del,
>> +    .intersects = amdgpu_dummy_vram_mgr_intersects,
>> +    .compatible = amdgpu_dummy_vram_mgr_compatible,
>> +    .debug    = amdgpu_dummy_vram_mgr_debug
>> +};
>> +
>>   static const struct ttm_resource_manager_func amdgpu_vram_mgr_func = {
>>       .alloc    = amdgpu_vram_mgr_new,
>>       .free    = amdgpu_vram_mgr_del,
>> @@ -841,17 +888,22 @@ int amdgpu_vram_mgr_init(struct amdgpu_device 
>> *adev)
>>       ttm_resource_manager_init(man, &adev->mman.bdev,
>>                     adev->gmc.real_vram_size);
>>   -    man->func = &amdgpu_vram_mgr_func;
>> -
>> -    err = drm_buddy_init(&mgr->mm, man->size, PAGE_SIZE);
>> -    if (err)
>> -        return err;
>> -
>>       mutex_init(&mgr->lock);
>>       INIT_LIST_HEAD(&mgr->reservations_pending);
>>       INIT_LIST_HEAD(&mgr->reserved_pages);
>>       mgr->default_page_size = PAGE_SIZE;
>>   +    if (!adev->gmc.is_app_apu) {
>> +        man->func = &amdgpu_vram_mgr_func;
>> +
>> +        err = drm_buddy_init(&mgr->mm, man->size, PAGE_SIZE);
>> +        if (err)
>> +            return err;
>> +    } else {
>> +        man->func = &amdgpu_dummy_vram_mgr_func;
>> +        DRM_INFO("Setup dummy vram mgr\n");
>> +    }
>> +
>>       ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, 
>> &mgr->manager);
>>       ttm_resource_manager_set_used(man, true);
>>       return 0;
>> @@ -886,7 +938,8 @@ void amdgpu_vram_mgr_fini(struct amdgpu_device 
>> *adev)
>>           drm_buddy_free_list(&mgr->mm, &rsv->allocated);
>>           kfree(rsv);
>>       }
>> -    drm_buddy_fini(&mgr->mm);
>> +    if (!adev->gmc.is_app_apu)
>> +        drm_buddy_fini(&mgr->mm);
>>       mutex_unlock(&mgr->lock);
>>         ttm_resource_manager_cleanup(man);
>