On Wed, 06 Feb 2013, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: > 770c12312ad617172b1a65b911d3e6564fc5aca8 is the first bad commit > commit 770c12312ad617172b1a65b911d3e6564fc5aca8 > Author: Takashi Iwai <tiwai at suse.de> > Date: Sat Aug 11 08:56:42 2012 +0200 > > drm/i915: Fix blank panel at reopening lid > > changed the register write sequence for restoring the backlight, which > helped prevent non-working backlights on some machines. Turns out that > the original sequence was the right thing to do for a different set of > machines. Worse, setting the backlight level _after_ enabling it seems > to reset it somehow. So we need to make that one conditional upon the > backlight having been reset to zero, and add the old one back. > > Cargo-culting at it's best, but it seems to work. > > Cc: stable at vger.kernel.org > Cc: Takashi Iwai <tiwai at suse.de> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=47941 > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> > --- > drivers/gpu/drm/i915/intel_panel.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c > index bee8cb6..a3730e0 100644 > --- a/drivers/gpu/drm/i915/intel_panel.c > +++ b/drivers/gpu/drm/i915/intel_panel.c > @@ -321,6 +321,9 @@ void intel_panel_enable_backlight(struct drm_device *dev, > if (dev_priv->backlight_level == 0) > dev_priv->backlight_level = intel_panel_get_max_backlight(dev); > > + dev_priv->backlight_enabled = true; > + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); > + > if (INTEL_INFO(dev)->gen >= 4) { > uint32_t reg, tmp; > > @@ -356,12 +359,12 @@ void intel_panel_enable_backlight(struct drm_device *dev, > } > > set_level: > - /* Call below after setting BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1. > - * BLC_PWM_CPU_CTL may be cleared to zero automatically when these > - * registers are set. > + /* Check the current backlight level and try to set again if it's zero. > + * On some machines, BLC_PWM_CPU_CTL is cleared to zero automatically > + * when BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1 are written. > */ > - dev_priv->backlight_enabled = true; > - intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); > + if (!intel_panel_get_backlight(dev)) > + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); Given how much pain the backlight keeps giving us, do you think we would benefit from sticking a DRM_DEBUG_DRIVER in the if block there? Either way, with a heavy *sigh*, Reviewed-by: Jani Nikula <jani.nikula at intel.com> > } > > static void intel_panel_init_backlight(struct drm_device *dev) > -- > 1.7.10.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx at lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
