[Intel-gfx] [PATCH 1/2] drm/i915: clear up backlight inversion confusion on gen4

[Daniel Vetter]

On Mon, Apr 23, 2012 at 02:32:57PM +0200, Daniel Vetter wrote:
> On Mon, Apr 23, 2012 at 01:54:23PM +0200, Carsten Emde wrote:
> > On 04/23/2012 11:32 AM, Daniel Vetter wrote:
> > >There's a bit in the docs for gen4 only that says whether the
> > >backlight control is inverted. And both the quirk we have and
> > >all bugs only concern i965gm and gm45 (and mostly Acer) afaics.
> > >
> > >So lets drop the quirk and use the bit instead.
> > >
> > >Also clean up the BLC register definitions a bit by correctly
> > >grouping the CTL and CTL2 definitions together.
> > >[..]
> > >diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > >index 4c844c6..5d215f0 100644
> > >--- a/drivers/gpu/drm/i915/intel_display.c
> > >+++ b/drivers/gpu/drm/i915/intel_display.c
> > >@@ -6482,9 +6482,6 @@ static struct intel_quirk intel_quirks[] = {
> > >
> > >  	/* Sony Vaio Y cannot use SSC on LVDS */
> > >  	{ 0x0046, 0x104d, 0x9076, quirk_ssc_force_disable },
> > >-
> > >-	/* Acer Aspire 5734Z must invert backlight brightness */
> > >-	{ 0x2a42, 0x1025, 0x0459, quirk_invert_brightness },
> > Made a first test with these lines removed and the new mechanism
> > added.  Unfortunately, the screen is now dark again. Works after
> > re-adding the quirk.
> > 
> > >+	/* gen4 has a polarity bit */
> > >+	if (IS_GEN4(dev) && (I915_READ(BLC_PWM_CTL2) & BLM_POLARITY_I965))
> > >+			return intel_panel_get_max_backlight(dev) - val;
> > >+
> > Apparently, these conditions are not met on the Acer Aspire 5734Z.
> > Will add some debug output and evaluate further. For the time being,
> > please leave the quirk in place.
> 
> Hm, I've tried this and when I set this bit, panel brightness is inverted
> on my gm45. Can you install intel-gpu-tools and read out the 2 backlight
> control registers with 
> 
> # intel_reg_read 0x61254
> # intel_reg_read 0x61250

I've forgotten to add: Also please grab these register values when booting
with nomodeset, so that we can compare the values the bios sets with
whatever i915 sets.
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48