lkml.org 
[lkml]   [2023]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] drm/atomic: Allow vblank-enabled + self-refresh "disable"
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@vger.kernel.org> # dependency for subsequent patch
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
>
> 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.

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.

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.
-Daniel

>
> ret = drm_crtc_vblank_get(crtc);
> WARN_ONCE(ret != -EINVAL, "driver forgot to call drm_crtc_vblank_off()\n");
> --
> 2.39.0.314.g84b9a713c41-goog
>

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

\
 
 \ /
  Last update: 2023-03-26 23:31    [W:0.141 / U:0.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site