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. > 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.) > 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. Brian [1] Link: https://lore.kernel.org/dri-devel/Y5itf0+yNIQa6fU4@xxxxxxxxxxxxx/ Reported-by: "kernelci.org bot" <bot@xxxxxxxxxxxx>
