Hi Am 10.09.19 um 13:52 schrieb Gerd Hoffmann: > 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 <[email protected]> >> --- >> 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
This lock is hold by the fbdev code during mode-setting operations (but not drawing operations). So *crtc might be gone if we don't hold it here. > helper->client.modesets? If so then you can unlock before going to > sleep in drm_crtc_wait_one_vblank() I think. I looked, but I cannot find any code that protects crtc while vblank is active. I'd rather not change the current code until someone can clarify. Best regards Thomas > > cheers, > Gerd > -- Thomas Zimmermann Graphics Driver Developer SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 21284 (AG Nürnberg)
signature.asc
Description: OpenPGP digital signature
_______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
