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

[Thomas Zimmermann]

Am 08.11.21 um 21:55 schrieb 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?

The value of dst_clip comes from plane_state->dst, which gets 
initialized in drm_atomic_helper_check_plane_state(). [1] The fields are 
taken from the crtc_{x,y,w,h} values by drm_plane_get_dest(). [2] For 
primary planes, the crtc_{x,y,w,h} values are initialized in 
__drm_atomic_helper_set_config() to the size of the display. [3] That 
size comes directly from the current video mode. [4] From all I can see 
this cannot overflow.

Best regards
Thomas

[1] 
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_atomic_helper.c#L807
[2] 
https://elixir.bootlin.com/linux/latest/source/include/drm/drm_plane.h#L257
[3] 
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_atomic.c#L1590
[4] 
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_modes.c#L788

> 
> 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;
>>

-- 
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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