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

[Daniel Vetter <daniel@ffwll.ch>]

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

Thanks, Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48