linux-kernel - Re: [PATCH 09/10] drm/qxl: map/unmap framebuffers in prepare_fb+cleanup

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Message-ID: <5baf096f-b1ee-46ba-5ee9-1c829b96e088@suse.de>
Date:   Tue, 16 Feb 2021 14:27:40 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Gerd Hoffmann <kraxel@...hat.com>, dri-devel@...ts.freedesktop.org
Cc:     David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@...ts.freedesktop.org>,
        Dave Airlie <airlied@...hat.com>
Subject: Re: [PATCH 09/10] drm/qxl: map/unmap framebuffers in
 prepare_fb+cleanup_fb callbacks.

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.

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@...hat.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);
> 

-- 
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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