On Mon, Sep 09, 2019 at 04:06:32PM +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.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index a7ba5b4902d6..017e2f6bd1b9 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -402,8 +402,20 @@ 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 */
> + mutex_lock(&helper->lock);
> + 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);
> + }
> + mutex_unlock(&helper->lock);
Hmm, not sure it is the best plan to sleep for a while in the worker,
especially while holding the lock.
What does the lock protect against here? Accessing
helper->client.modesets? If so then you can unlock before going to
sleep in drm_crtc_wait_one_vblank() I think.
cheers,
Gerd
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