[Intel-gfx] [PATCH] drm/atomic: Introduce drm_atomic_helper_shutdown

[Tomi Valkeinen]

On 27/03/17 10:43, Daniel Vetter wrote:

> With atomic we've stopped killing the entire CRTC when you the last
> userspace reference for the framebuffer on the primary plane disappears,
> but just shut down the primary plane. Assuming the driver can do that, we
> fall back to full CRTC shutdown if not. That avoids a pile of flickering
> and unecessary modesets.
> 
> But yeah downside is that the crtc is active even when unloading. Note

Not only that, but also when you stop a DRM userspace app and don't
start a new one, the crtc stays active. Maybe that's not so common
scenario, but I wouldn't be that surprised if on embedded world someone
only runs a DRM app when they're showing something, and no app in
between the runs.

What makes the behavior a bit funny is that if I boot without fbdev
emulation, the crtcs stay off (as they should). But run a DRM app, quit
it, and the crtcs are on.

This is a bit related to the other annoyance, which is that we don't
reset properties when a DRM app quits. I think the state of the HW
should be restored to exactly the same state as it was (including
turning off the crtcs). I'm planning to have a look at this whenever I
happen to find some time...

 Tomi

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