在 2026-05-22五的 11:23 +0200，Maarten Lankhorst写道： > Hey, > > Den 2026-05-19 kl. 13:29, skrev Icenowy Zheng: > > 在 2026-05-19二的 12:41 +0300，Jani Nikula写道： > > > On Tue, 19 May 2026, Icenowy Zheng <[email protected]> > > > wrote: > > > > Currently the implementaion of > > > > drm_client_modeset_wait_for_vblank() > > > > assumes drm_vblank_get() will fail when the CRTC isn't active. > > > > However > > > > it seems that this is not true, and running fbcon on a device > > > > with > > > > the > > > > first CRTC inactive will lead to kernel warning in some cases > > > > (which > > > > could be reproduced with the loongson driver). > > > > > > > > Change the implementation to add a check for the active state > > > > (atomic) / > > > > enabled state (non-atomic) before calling drm_vblank_get(). As > > > > the > > > > assumption of drm_vblank_get() failing for inactive CRTC isn't > > > > met, > > > > the > > > > error status of drm_vblank_get() can now be exported too. > > > > > > > > Cc: [email protected] > > > > Fixes: d8c4bddcd8bc ("drm/fb-helper: Synchronize dirty worker > > > > with > > > > vblank") > > > > Signed-off-by: Icenowy Zheng <[email protected]> > > > > --- > > > > drivers/gpu/drm/drm_client_modeset.c | 13 +++++++++++-- > > > > 1 file changed, 11 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/drm_client_modeset.c > > > > b/drivers/gpu/drm/drm_client_modeset.c > > > > index bb49b8361271a..1b03bf351256e 100644 > > > > --- a/drivers/gpu/drm/drm_client_modeset.c > > > > +++ b/drivers/gpu/drm/drm_client_modeset.c > > > > @@ -1310,7 +1310,7 @@ int > > > > drm_client_modeset_wait_for_vblank(struct > > > > drm_client_dev *client, unsigned i > > > > { > > > > struct drm_device *dev = client->dev; > > > > struct drm_crtc *crtc; > > > > - int ret; > > > > + int ret = 0; > > > > > > > > /* > > > > * Rate-limit update frequency to vblank. If there's a > > > > DRM > > > > master > > > > @@ -1326,15 +1326,24 @@ int > > > > drm_client_modeset_wait_for_vblank(struct drm_client_dev > > > > *client, > > > > unsigned i > > > > * Only wait for a vblank event if the CRTC is > > > > enabled, > > > > otherwise > > > > * just don't do anything, not even report an error. > > > > */ > > > > > > I'll dodge the question whether the change below is right or not, > > > but > > > for sure the comment above needs to be amended to match the > > > change. > > > > If the change is right, it perfectly matches what the comment above > > is > > saying -- it's the current behavior that does not match the > > comment. > > > > Thanks, > > Icenowy > I would rather have expected drm_fb_helper_ioctl to fail like you > mention. > Probably needs a fbcon_is_active() there to prevent it. > > The damage helper should not be triggered if no CRTC is active, so > that means > the check here is slightly too late.
Well the problem here seems to be a CRTC is active, but it's not CRTC 0 (for embedded hardwares CRTCs could be somehow fixed and tied to physical ports); and the fbdev helpers hardcode 0 as the CRTC ID. Thanks, Icenowy > > Can you fix it at a different level, like damage helper or its > callers instead? > > I believe when the client gets suspended, all the pending damage is > flushed before > suspend. > > Kind regards, > ~Maarten Lankhorst
