[Bug 80182] [IVB regression] screen not resuming on kernel 3.14.6 and above

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=80182

--- Comment #36 from Hans de Goede <jwrdegoede at fedoraproject.org> ---
(In reply to Jani Nikula from comment #35)
> Indeed the logs have plenty of
> 
> [  873.096139] [drm:intel_backlight_device_update_status], updating
> intel_backlight, brightness=0/4437
> 
> indicating userspace wishing to dim the backlight.

Hmm, so this may not be a kernel bug at all. Actually with this info, this
sounds a lot like an xf86-video-intel bug which I fixed a while back,
specifically see:

http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=b545e10c50cbb2dd6f9fd53369667bed0d8f1b51

Without that commit when userspace does a dpms off and then a read/modify/write
of the backlight level things may end up with a backlight level of 0.

Also possibly relevant is:

http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=c6cd10f536e099277cdc46643725a5a50ea8b525

And then specifically this bit:

@@ -820,6 +949,14 @@ sna_crtc_apply(xf86CrtcPtr crtc)
for (i = 0; i < config->num_output; i++) {
xf86OutputPtr output = config->output[i];
+ /* Make sure we mark the output as off (and save the backlight)
+ * before the kernel turns it off due to changing the pipe.
+ * This is necessary as the kernel may turn off the backlight
+ * and we lose track of the user settings.
+ */
+ if (output->crtc == NULL)
+ output->funcs->dpms(output, DPMSModeOff);
+
if (output->crtc != crtc)
continue;

Marian, can you please try upgrading your intel driver to the 2.99.916 release
? (you can download the tarbal and build it from source), and please make sure
you're using sna and not uxa.

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