Re: [PATCH 09/10] drm/qxl: map/unmap framebuffers in prepare_fb+cleanup_fb callbacks.

[Thomas Zimmermann <tzimmermann@suse.de>]

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Am 16.02.21 um 14:27 schrieb Thomas Zimmermann:
> Hi
> 
> this is a shadow-buffered plane. Did you consider using the new helpers 
> for shadow-buffered planes? They will map the user BO for you and 
> provide the mapping in the plane state.
> 
>  From there, you should implement your own plane state on top of struct 
> drm_shadow_plane_state, and also move all the other allocations and 
> vmaps into prepare_fb and cleanup_fb. Most of this is not actually 
> allowed in commit tails. All we'd have to do is to export the reset, 
> duplicate and destroy code; similar to what 
> __drm_atomic_helper_plane_reset() does.

AFAICT the cursor_bo is used to implement double buffering for the 
cursor image.

Ideally, you can do what ast does: pre-allocate/vmap 2 BOs at the end of 
the vram. Then pageflip between them in atomic_update(). Resolves all 
the allocation and mapping headaches.

Best regards
Thomas

> 
> Best regards
> Thomas
> 
> 
> Am 16.02.21 um 12:37 schrieb Gerd Hoffmann:
>> We don't have to map in atomic_update callback then,
>> making locking a bit less complicated.
>>
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>>   drivers/gpu/drm/qxl/qxl_display.c | 14 +++++---------
>>   1 file changed, 5 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/qxl/qxl_display.c 
>> b/drivers/gpu/drm/qxl/qxl_display.c
>> index 7500560db8e4..39b8c5116d34 100644
>> --- a/drivers/gpu/drm/qxl/qxl_display.c
>> +++ b/drivers/gpu/drm/qxl/qxl_display.c
>> @@ -584,7 +584,6 @@ static void qxl_cursor_atomic_update(struct 
>> drm_plane *plane,
>>       struct drm_gem_object *obj;
>>       struct qxl_bo *cursor_bo = NULL, *user_bo = NULL, *old_cursor_bo 
>> = NULL;
>>       int ret;
>> -    struct dma_buf_map user_map;
>>       struct dma_buf_map cursor_map;
>>       void *user_ptr;
>>       int size = 64*64*4;
>> @@ -599,11 +598,8 @@ static void qxl_cursor_atomic_update(struct 
>> drm_plane *plane,
>>           obj = fb->obj[0];
>>           user_bo = gem_to_qxl_bo(obj);
>> -        /* pinning is done in the prepare/cleanup framevbuffer */
>> -        ret = qxl_bo_kmap_locked(user_bo, &user_map);
>> -        if (ret)
>> -            goto out_free_release;
>> -        user_ptr = user_map.vaddr; /* TODO: Use mapping abstraction 
>> properly */
>> +        /* mapping is done in the prepare/cleanup framevbuffer */
>> +        user_ptr = user_bo->map.vaddr; /* TODO: Use mapping 
>> abstraction properly */
>>           ret = qxl_alloc_bo_reserved(qdev, release,
>>                           sizeof(struct qxl_cursor) + size,
>> @@ -639,7 +635,6 @@ static void qxl_cursor_atomic_update(struct 
>> drm_plane *plane,
>>           cursor->chunk.data_size = size;
>>           memcpy(cursor->chunk.data, user_ptr, size);
>>           qxl_bo_kunmap_locked(cursor_bo);
>> -        qxl_bo_kunmap_locked(user_bo);
>>           cmd = (struct qxl_cursor_cmd *) qxl_release_map(qdev, release);
>>           cmd->u.set.visible = 1;
>> @@ -778,6 +773,7 @@ static int qxl_plane_prepare_fb(struct drm_plane 
>> *plane,
>>       struct drm_gem_object *obj;
>>       struct qxl_bo *user_bo;
>>       struct qxl_surface surf;
>> +    struct dma_buf_map unused;
>>       if (!new_state->fb)
>>           return 0;
>> @@ -815,7 +811,7 @@ static int qxl_plane_prepare_fb(struct drm_plane 
>> *plane,
>>           }
>>       }
>> -    return qxl_bo_pin(user_bo);
>> +    return qxl_bo_kmap(user_bo, &unused);
>>   }
>>   static void qxl_plane_cleanup_fb(struct drm_plane *plane,
>> @@ -834,7 +830,7 @@ static void qxl_plane_cleanup_fb(struct drm_plane 
>> *plane,
>>       obj = old_state->fb->obj[0];
>>       user_bo = gem_to_qxl_bo(obj);
>> -    qxl_bo_unpin(user_bo);
>> +    qxl_bo_kunmap(user_bo);
>>       if (old_state->fb != plane->state->fb && user_bo->shadow) {
>>           qxl_bo_unpin(user_bo->shadow);
>>
> 
> 
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> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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