[PATCH v2 7/9] drm/simpledrm: Enable FB_DAMAGE_CLIPS property

[Noralf Trønnes]

Den 01.11.2021 15.15, skrev Thomas Zimmermann:
> Enable the FB_DAMAGE_CLIPS property to reduce display-update
> overhead. Also fixes a warning in the kernel log.
> 
>   simple-framebuffer simple-framebuffer.0: [drm] drm_plane_enable_fb_damage_clips() not called
> 
> Fix the computation of the blit rectangle. This wasn't an issue so
> far, as simpledrm always blitted the full framebuffer. The code now
> supports damage clipping and virtual screen sizes.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---
>  drivers/gpu/drm/tiny/simpledrm.c | 30 ++++++++++++++++++++++--------
>  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
> index 571f716ff427..e872121e9fb0 100644
> --- a/drivers/gpu/drm/tiny/simpledrm.c
> +++ b/drivers/gpu/drm/tiny/simpledrm.c
> @@ -642,7 +642,7 @@ simpledrm_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
>  	void *vmap = shadow_plane_state->data[0].vaddr; /* TODO: Use mapping abstraction */
>  	struct drm_device *dev = &sdev->dev;
>  	void __iomem *dst = sdev->screen_base;
> -	struct drm_rect clip;
> +	struct drm_rect src_clip, dst_clip;
>  	int idx;
>  
>  	if (!fb)
> @@ -651,10 +651,14 @@ simpledrm_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
>  	if (!drm_dev_enter(dev, &idx))
>  		return;
>  
> -	drm_rect_init(&clip, 0, 0, fb->width, fb->height);
> +	drm_rect_fp_to_int(&src_clip, &plane_state->src);
>  
> -	dst += drm_fb_clip_offset(sdev->pitch, sdev->format, &clip);
> -	drm_fb_blit_toio(dst, sdev->pitch, sdev->format->format, vmap, fb, &clip);
> +	dst_clip = plane_state->dst;

I assume that src_clip and dst_clip are of the same size, since scaling
is not supported. What prevents dst_clip from being bigger than the
buffer that's being blitted into? Where is that bounds checking done?

Noralf.

> +	if (!drm_rect_intersect(&dst_clip, &src_clip))
> +		return;
> +
> +	dst += drm_fb_clip_offset(sdev->pitch, sdev->format, &dst_clip);
> +	drm_fb_blit_toio(dst, sdev->pitch, sdev->format->format, vmap, fb, &src_clip);
>  
>  	drm_dev_exit(idx);
>  }
> @@ -686,20 +690,28 @@ simpledrm_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
>  	struct drm_framebuffer *fb = plane_state->fb;
>  	struct drm_device *dev = &sdev->dev;
>  	void __iomem *dst = sdev->screen_base;
> -	struct drm_rect clip;
> +	struct drm_rect damage_clip, src_clip, dst_clip;
>  	int idx;
>  
>  	if (!fb)
>  		return;
>  
> -	if (!drm_atomic_helper_damage_merged(old_plane_state, plane_state, &clip))
> +	if (!drm_atomic_helper_damage_merged(old_plane_state, plane_state, &damage_clip))
> +		return;
> +
> +	drm_rect_fp_to_int(&src_clip, &plane_state->src);
> +	if (!drm_rect_intersect(&src_clip, &damage_clip))
> +		return;
> +
> +	dst_clip = plane_state->dst;
> +	if (!drm_rect_intersect(&dst_clip, &src_clip))
>  		return;
>  
>  	if (!drm_dev_enter(dev, &idx))
>  		return;
>  
> -	dst += drm_fb_clip_offset(sdev->pitch, sdev->format, &clip);
> -	drm_fb_blit_toio(dst, sdev->pitch, sdev->format->format, vmap, fb, &clip);
> +	dst += drm_fb_clip_offset(sdev->pitch, sdev->format, &dst_clip);
> +	drm_fb_blit_toio(dst, sdev->pitch, sdev->format->format, vmap, fb, &src_clip);
>  
>  	drm_dev_exit(idx);
>  }
> @@ -794,6 +806,8 @@ static int simpledrm_device_init_modeset(struct simpledrm_device *sdev)
>  	if (ret)
>  		return ret;
>  
> +	drm_plane_enable_fb_damage_clips(&pipe->plane);
> +
>  	drm_mode_config_reset(dev);
>  
>  	return 0;
>