Screen doesn't stay powered off on suspend

[Michael Hall]

When suspending (by pressing the power button) on a Nexus 7, the screen backlight will cycle on and off repeatedly.

[Dave Morley (davmor2)]

You'll only really notice this if it is in a shaded place in a bright place you hardly spot it .

[Sebastien Bacher (seb128)]

confirmed on current saucy, that's still an issue

[Seth Forshee (sforshee)]

There are two problems here. I don't believe either of them are powerd's.

1. Setting the backlight level to 0 doesn't disable it, and it doesn't disable when the fb is blanked either. The only way to actually turn it off seems to be to suspend. I've got a kernel patch that makes brightnes=0 == screen off which at least masks the issue, but I'm still wondering what Android does.

Okay, so it turns out Android does exactly what my patch does. Apparently we patched the kernel a long time ago so that 0 brightness doesn't turn the screen off. I'll change it back.

2. Something in the graphics driver is failing to suspend. So what happens is that the kernel keeps trying to suspend over and over again. Each time some of the devices suspend, then the graphics driver fails and the already suspended devices are resumed. One of the ones getting repeatedly suspended and resumed is the backlight device, which is what causes it to cycle on and off. It's masked by my patch for issue #1, but fixing the failed suspends will require more investigation.

[Seth Forshee (sforshee)]

Marking the powerd task invalid since the problems are in the kernel. I'm going to limit this bug to addressing issue #1 (backlight will not turn off) and open a new bug for issue #2 (suspend failures).

[Seth Forshee (sforshee)]

Opened bug #1192428 for the suspend failures.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-grouper - 3.1.10-6.14

---------------
linux-grouper (3.1.10-6.14) saucy; urgency=low

  [ Tim Gardner ]

  * Revert "SAUCE: prevent the brightness from going all the way off when
    using the brightness slider."
    - LP: #1187867
  * [Config] CONFIG_FRAMEBUFFER_CONSOLE=n
  * Fix insertchanges for grouper
 -- Tim Gardner <email address hidden> Wed, 19 Jun 2013 06:30:12 -0600