On Wed, Jun 20, 2012 at 11:21:11AM +0200, Takashi Iwai wrote: > At Wed, 20 Jun 2012 10:05:12 +0200, > Daniel Vetter wrote: > > > > On Wed, Jun 20, 2012 at 09:17:41AM +0200, Takashi Iwai wrote: > > > This patch fixes the problem on some HP desktop machines with eDP > > > which give blank screens after S3 resume. > > > > > > The problem looks like a timing issue. Although BLC_PWM_CPU_CTL > > > register is already restored at the beginning of resume, it doesn't > > > seem to take effect. Simply re-issuing the register write restores > > > the backlight gracefully. > > > > > > Tested with 3.5-rc3 kernel. > > > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49233 > > > > > > Signed-off-by: Takashi Iwai <tiwai at suse.de> > > > > This patch looks very fishy as-is, simply because I don't like adding > > random calls to random functions at pretty much random places without any > > hint why it works. > > It's difficult to know exactly why it works. We can only guess, but > nothing more than that, just like between husband and wife :) Yeah I know, but I've been burnt a bit recently with too much cargo-culting. Hence why I'm so dense about this stuff ;-) > > Just a few weeks ago we've had tons of fun with writes > > that don't stick when the ring isn't yet set up. Can you please check with > > a bunch of printks what exactly happens to the value of BLC_PWM_CPU_CTL? > > I.e. whether the write doesn't stick or whether it gets reset somewhere > > between the register restore functions and the new place. > > The register value is already set, and not touched after that. > I've already checked. So immediately before the backlight_update_status call we have the _correct_ value in BLC_PWM_CPU_CTL? That would be indeed puzzling ... > > I suspect the opregion_init call could allow the bios to frob with these > > registers. If that's the case, the patch is missing a comment that to that > > effect. > > Right. That's also my suspect. > > > Essentially I want to know why this place here works and why not move the > > call a few lines up or down. > > A few lines down works definitely. Even just writing to sysfs works. > A few lines up, well, I need to check where is the border line. Thanks, that would be interesting. Especially if it's opregion that we need to have set up before restoring the backlight properly. -Daniel > > > Takashi > > > -Daniel > > > > > --- > > > drivers/gpu/drm/i915/i915_drv.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c > > > index 9fe9ebe..2ba1350 100644 > > > --- a/drivers/gpu/drm/i915/i915_drv.c > > > +++ b/drivers/gpu/drm/i915/i915_drv.c > > > @@ -658,6 +658,9 @@ static int i915_drm_thaw(struct drm_device *dev) > > > > > > intel_opregion_init(dev); > > > > > > + if (dev_priv->backlight) > > > + backlight_update_status(dev_priv->backlight); > > > + > > > dev_priv->modeset_on_lid = 0; > > > > > > console_lock(); > > > -- > > > 1.7.10.4 > > > > > > _______________________________________________ > > > Intel-gfx mailing list > > > Intel-gfx at lists.freedesktop.org > > > http://lists.freedesktop.org/mailman/listinfo/intel-gfx > > > > -- > > Daniel Vetter > > Mail: daniel at ffwll.ch > > Mobile: +41 (0)79 365 57 48 > > -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
