On Fri, Jan 06, 2023 at 10:08:53AM -0800, Brian Norris wrote: > Hi Daniel, > > On Fri, Jan 06, 2023 at 06:53:49PM +0100, Daniel Vetter wrote: > > On Thu, Jan 05, 2023 at 05:40:17PM -0800, Brian Norris wrote: > > > The self-refresh helper framework overloads "disable" to sometimes mean > > > "go into self-refresh mode," and this mode activates automatically > > > (e.g., after some period of unchanging display output). In such cases, > > > the display pipe is still considered "on", and user-space is not aware > > > that we went into self-refresh mode. Thus, users may expect that > > > vblank-related features (such as DRM_IOCTL_WAIT_VBLANK) still work > > > properly. > > > > > > However, we trigger the WARN_ONCE() here if a CRTC driver tries to leave > > > vblank enabled here. > > > > > > Add a new exception, such that we allow CRTCs to be "disabled" (with > > > self-refresh active) with vblank interrupts still enabled. > > > > > > Cc: <stable@xxxxxxxxxxxxxxx> # dependency for subsequent patch > > > Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx> > > > --- > > > > > > drivers/gpu/drm/drm_atomic_helper.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > > > index d579fd8f7cb8..7b5eddadebd5 100644 > > > --- a/drivers/gpu/drm/drm_atomic_helper.c > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c > > > @@ -1207,6 +1207,12 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state) > > > > > > if (!drm_dev_has_vblank(dev)) > > > continue; > > > + /* > > > + * Self-refresh is not a true "disable"; let vblank remain > > > + * enabled. > > > + */ > > > + if (new_crtc_state->self_refresh_active) > > > + continue; > > > > This very fishy, because we check in crtc_needs_disable whether this > > output should stay on due to self-refresh. Which means you should never > > end up in here. > > That's not what crtc_needs_disable() does w.r.t. self-refresh. In fact, > it's the opposite; see, for example, the > |new_state->self_refresh_active| clause. That clause means that if we're > entering self-refresh, we *intend* to disable (i.e., we return 'true'). > That's because like I mention above, the self-refresh helpers overload > what "disable" means. > > I'll also add my caveat again that I'm a bit new to DRM, so feel free to > continue to correct me if I'm wrong :) Or perhaps Sean Paul could > provide second opinions, as I believe he wrote this stuff. I already replied in another thread with hopefully less nonsense from my side :-) > > And yes vblank better work in self refresh :-) If it doesn't, then you > > need to fake it with a timer, that's at least what i915 has done for > > transparent self-refresh. > > OK! Then that sounds like it at least ACKs my general idea for this > series. (Michel and I poked at a few ideas in the thread at [1] and > landed on approx. this solution, or else a fake/timer like you suggest.) Yeah once I stopped looking at this the wrong way round it does make sense what you're doing. See my other reply, I think with just this series here the vblanks still stall out? Or does your hw actually keep generating vblank irq with the display off? > > We might need a few more helpers. Also, probably more igt, or is this > > something igt testing has uncovered? If so, please cite the igt testcase > > which hits this. > > The current patch only fixes a warning that comes when I try to do the > second patch. The second patch is a direct product of an IGT test > failure (a few of kms_vblank's subtests), and I linked [1] the KernelCI > report there. Ah yeah that makes sense. Would be good to cite that in this patch too, because I guess the same kms_vblank tests can also hit this warning here? -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
