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

Carsten Emde
2012-04-23T15:44:11Z

On 04/23/2012 05:22 PM, Daniel Vetter wrote:
> 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:
>>> [..]
>>> 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
Here we go.

-> Initial screen: dark

# intel_reg_write 0x61250 0xd0000000
Value before: 0xE0000000
Value after: 0xD0000000
-> BACKLIGHT ON!

# intel_reg_write 0x61250 0xc0000000
Value before: 0xD0000000
Value after: 0xC0000000
-> Dark again.

-Carsten.