Re: [PATCH v2 5/6] drm/gud: Use the shadow plane helper

[Thomas Zimmermann <tzimmermann@suse.de>]

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Am 30.11.22 um 20:26 schrieb Noralf Trønnes via B4 Submission Endpoint:
> From: Noralf Trønnes <noralf@tronnes.org>
> 
> Use the shadow plane helper to take care of mapping the framebuffer for
> CPU access. The synchronous flushing is now done inline without the use of
> a worker. The async path now uses a shadow buffer to hold framebuffer
> changes and it doesn't read the framebuffer behind userspace's back
> anymore.
> 
> v2:
> - Use src as variable name for iosys_map (Thomas)
> - Prepare imported buffer for CPU access in the driver (Thomas)
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

> ---
>   drivers/gpu/drm/gud/gud_drv.c      |  1 +
>   drivers/gpu/drm/gud/gud_internal.h |  1 +
>   drivers/gpu/drm/gud/gud_pipe.c     | 81 ++++++++++++++++++++++++++------------
>   3 files changed, 57 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/gud/gud_drv.c b/drivers/gpu/drm/gud/gud_drv.c
> index d57dab104358..5aac7cda0505 100644
> --- a/drivers/gpu/drm/gud/gud_drv.c
> +++ b/drivers/gpu/drm/gud/gud_drv.c
> @@ -365,6 +365,7 @@ static void gud_debugfs_init(struct drm_minor *minor)
>   static const struct drm_simple_display_pipe_funcs gud_pipe_funcs = {
>   	.check      = gud_pipe_check,
>   	.update	    = gud_pipe_update,
> +	DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS
>   };
>   
>   static const struct drm_mode_config_funcs gud_mode_config_funcs = {
> diff --git a/drivers/gpu/drm/gud/gud_internal.h b/drivers/gpu/drm/gud/gud_internal.h
> index e351a1f1420d..0d148a6f27aa 100644
> --- a/drivers/gpu/drm/gud/gud_internal.h
> +++ b/drivers/gpu/drm/gud/gud_internal.h
> @@ -43,6 +43,7 @@ struct gud_device {
>   	struct drm_framebuffer *fb;
>   	struct drm_rect damage;
>   	bool prev_flush_failed;
> +	void *shadow_buf;
>   };
>   
>   static inline struct gud_device *to_gud_device(struct drm_device *drm)
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 98fe8efda4a9..92189474a7ed 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -358,10 +358,10 @@ static void gud_flush_damage(struct gud_device *gdrm, struct drm_framebuffer *fb
>   void gud_flush_work(struct work_struct *work)
>   {
>   	struct gud_device *gdrm = container_of(work, struct gud_device, work);
> -	struct iosys_map gem_map = { }, fb_map = { };
> +	struct iosys_map shadow_map;
>   	struct drm_framebuffer *fb;
>   	struct drm_rect damage;
> -	int idx, ret;
> +	int idx;
>   
>   	if (!drm_dev_enter(&gdrm->drm, &idx))
>   		return;
> @@ -369,6 +369,7 @@ void gud_flush_work(struct work_struct *work)
>   	mutex_lock(&gdrm->damage_lock);
>   	fb = gdrm->fb;
>   	gdrm->fb = NULL;
> +	iosys_map_set_vaddr(&shadow_map, gdrm->shadow_buf);
>   	damage = gdrm->damage;
>   	gud_clear_damage(gdrm);
>   	mutex_unlock(&gdrm->damage_lock);
> @@ -376,33 +377,33 @@ void gud_flush_work(struct work_struct *work)
>   	if (!fb)
>   		goto out;
>   
> -	ret = drm_gem_fb_vmap(fb, &gem_map, &fb_map);
> -	if (ret)
> -		goto fb_put;
> +	gud_flush_damage(gdrm, fb, &shadow_map, true, &damage);
>   
> -	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> -	if (ret)
> -		goto vunmap;
> -
> -	/* Imported buffers are assumed to be WriteCombined with uncached reads */
> -	gud_flush_damage(gdrm, fb, &fb_map, !fb->obj[0]->import_attach, &damage);
> -
> -	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
> -vunmap:
> -	drm_gem_fb_vunmap(fb, &gem_map);
> -fb_put:
>   	drm_framebuffer_put(fb);
>   out:
>   	drm_dev_exit(idx);
>   }
>   
> -static void gud_fb_queue_damage(struct gud_device *gdrm, struct drm_framebuffer *fb,
> -				struct drm_rect *damage)
> +static int gud_fb_queue_damage(struct gud_device *gdrm, struct drm_framebuffer *fb,
> +			       const struct iosys_map *src, struct drm_rect *damage)
>   {
>   	struct drm_framebuffer *old_fb = NULL;
> +	struct iosys_map shadow_map;
>   
>   	mutex_lock(&gdrm->damage_lock);
>   
> +	if (!gdrm->shadow_buf) {
> +		gdrm->shadow_buf = vzalloc(fb->pitches[0] * fb->height);
> +		if (!gdrm->shadow_buf) {
> +			mutex_unlock(&gdrm->damage_lock);
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	iosys_map_set_vaddr(&shadow_map, gdrm->shadow_buf);
> +	iosys_map_incr(&shadow_map, drm_fb_clip_offset(fb->pitches[0], fb->format, damage));
> +	drm_fb_memcpy(&shadow_map, fb->pitches, src, fb, damage);
> +
>   	if (fb != gdrm->fb) {
>   		old_fb = gdrm->fb;
>   		drm_framebuffer_get(fb);
> @@ -420,6 +421,26 @@ static void gud_fb_queue_damage(struct gud_device *gdrm, struct drm_framebuffer
>   
>   	if (old_fb)
>   		drm_framebuffer_put(old_fb);
> +
> +	return 0;
> +}
> +
> +static void gud_fb_handle_damage(struct gud_device *gdrm, struct drm_framebuffer *fb,
> +				 const struct iosys_map *src, struct drm_rect *damage)
> +{
> +	int ret;
> +
> +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
> +		drm_rect_init(damage, 0, 0, fb->width, fb->height);
> +
> +	if (gud_async_flush) {
> +		ret = gud_fb_queue_damage(gdrm, fb, src, damage);
> +		if (ret != -ENOMEM)
> +			return;
> +	}
> +
> +	/* Imported buffers are assumed to be WriteCombined with uncached reads */
> +	gud_flush_damage(gdrm, fb, src, !fb->obj[0]->import_attach, damage);
>   }
>   
>   int gud_pipe_check(struct drm_simple_display_pipe *pipe,
> @@ -544,10 +565,11 @@ void gud_pipe_update(struct drm_simple_display_pipe *pipe,
>   	struct drm_device *drm = pipe->crtc.dev;
>   	struct gud_device *gdrm = to_gud_device(drm);
>   	struct drm_plane_state *state = pipe->plane.state;
> +	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
>   	struct drm_framebuffer *fb = state->fb;
>   	struct drm_crtc *crtc = &pipe->crtc;
>   	struct drm_rect damage;
> -	int idx;
> +	int ret, idx;
>   
>   	if (crtc->state->mode_changed || !crtc->state->enable) {
>   		cancel_work_sync(&gdrm->work);
> @@ -557,6 +579,8 @@ void gud_pipe_update(struct drm_simple_display_pipe *pipe,
>   			gdrm->fb = NULL;
>   		}
>   		gud_clear_damage(gdrm);
> +		vfree(gdrm->shadow_buf);
> +		gdrm->shadow_buf = NULL;
>   		mutex_unlock(&gdrm->damage_lock);
>   	}
>   
> @@ -572,14 +596,19 @@ void gud_pipe_update(struct drm_simple_display_pipe *pipe,
>   	if (crtc->state->active_changed)
>   		gud_usb_set_u8(gdrm, GUD_REQ_SET_DISPLAY_ENABLE, crtc->state->active);
>   
> -	if (drm_atomic_helper_damage_merged(old_state, state, &damage)) {
> -		if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
> -			drm_rect_init(&damage, 0, 0, fb->width, fb->height);
> -		gud_fb_queue_damage(gdrm, fb, &damage);
> -		if (!gud_async_flush)
> -			flush_work(&gdrm->work);
> -	}
> +	if (!fb)
> +		goto ctrl_disable;
>   
> +	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
> +	if (ret)
> +		goto ctrl_disable;
> +
> +	if (drm_atomic_helper_damage_merged(old_state, state, &damage))
> +		gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +
> +	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
> +
> +ctrl_disable:
>   	if (!crtc->state->enable)
>   		gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 0);
>   
> 

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

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