[PATCH v2 1/3] drm/fb-helper: Synchronize dirty worker with vblank

[Gerd Hoffmann]

On Thu, Sep 12, 2019 at 08:42:28AM +0200, Thomas Zimmermann wrote:
> Before updating the display from the console's shadow buffer, the dirty
> worker now waits for vblank. This allows several screen updates to pile
> up and acts as a rate limiter.
> 
> v2:
> 	* don't hold helper->lock while waiting for vblank
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>#

Reviewed-by: Gerd Hoffmann <kraxel at redhat.com>

> ---
>  drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index a7ba5b4902d6..d0cb1fa4f909 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -402,8 +402,18 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>  						    dirty_work);
>  	struct drm_clip_rect *clip = &helper->dirty_clip;
>  	struct drm_clip_rect clip_copy;
> +	struct drm_crtc *crtc;
>  	unsigned long flags;
>  	void *vaddr;
> +	int ret;
> +
> +	/* rate-limit update frequency */
> +	crtc = helper->client.modesets[0].crtc;
> +	ret = drm_crtc_vblank_get(crtc);
> +	if (!ret) {
> +		drm_crtc_wait_one_vblank(crtc);
> +		drm_crtc_vblank_put(crtc);
> +	}
>  
>  	spin_lock_irqsave(&helper->dirty_lock, flags);
>  	clip_copy = *clip;
> -- 
> 2.23.0
>