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

Daniel Vetter
2012-04-23T15:21:52Z

On Mon, Apr 23, 2012 at 05:06:53PM +0200, Carsten Emde wrote:
> On 04/23/2012 04:22 PM, Daniel Vetter wrote:
> >On Mon, Apr 23, 2012 at 04:00:23PM +0200, Carsten Emde wrote:
> >># intel_reg_write 0x61250 0x80000000
> >>Value before: 0xE0000000
> >>Value after: 0x80000000
> >># intel_reg_read 0x61254
> >>0x61254 : 0xB4A0B4A
> >>
> >># intel_reg_write 0x61250 0xa0000000
> >>Value before: 0x80000000
> >>Value after: 0xA0000000
> >># intel_reg_read 0x61254
> >>0x61254 : 0xB4A0B4A
> >>
> >># intel_reg_write 0x61250 0x90000000
> >>Value before: 0xA0000000
> >>Value after: 0x90000000
> >># intel_reg_read 0x61254
> >>0x61254 : 0xB4A0B4A
> >>
> >># intel_reg_write 0x61250 0xb0000000
> >>Value before: 0x90000000
> >>Value after: 0xB0000000
> >># intel_reg_read 0x61254
> >>0x61254 : 0xB4A0B4A
> >>
> >>Not much.
> >
> >The idea was to boot with kms and see whether any of these values would
> >restore the backlight. Writing to CTL1 should change anything in CTL2.
> Ah, sorry, ok. Removed the quirk again and tested the various settings:
>
> -> Initial screen: dark
>
> # intel_reg_write 0x61250 0x80000000
> Value before: 0xE0000000
> Value after: 0x80000000
> -> Still dark
>
> # intel_reg_write 0x61250 0xa0000000
> Value before: 0x80000000
> Value after: 0xA0000000
> -> Still dark
>
> # intel_reg_write 0x61250 0x90000000
> Value before: 0xA0000000
> Value after: 0x90000000
> -> BACKLIGHT ON!
>
> # intel_reg_write 0x61250 0xb0000000
> Value before: 0x90000000
> Value after: 0xB0000000
> -> Still ON.

Neat. Let's test two more:

# intel_reg_write 0x61250 0xd0000000
# intel_reg_write 0x61250 0xc0000000

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