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Re: [Libreboot] X60 tablet: screen whine after 1400x1050 screen swap

From: Michał Masłowski
Subject: Re: [Libreboot] X60 tablet: screen whine after 1400x1050 screen swap
Date: Sat, 18 Apr 2015 09:17:01 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux)

> I still can't read the value with devmem2 anyway - it always returns
> 0)

GPU registers region is probably allocated at a different address if you
see anything on the screen.

> gpu_backlight = 0x879f87da
> backlight modulation frequency = 180.016706 Hz

libreboot default?

> About the intel_bios_reader, I passed the oprom_0.rom and got the
> attached output. Apparently it still thinks I have a type 2 (1024x768)
> panel instead of the1400x1050 (type 4 or 5) I installed.

It specifies 165 Hz: 0x93F393F2 is an appropriate register value.

I'm not sure if Lenovo BIOS requires changes to support different screens.

> None of the frequencies match. (180 vs 122 vs 162)
> Previously, 0x879f879e gave the uneven backlight problem.
> Using 0x79417940 everything works fine, but with a lesser whine -- yet
> gives me that 0x879f87da or 0x879f87e6 when I tweak the
> brightness

How are you setting that value?  Check "lspci -vn -d 8086:27a2", see
where the smaller (register) memory region is allocated: the backlight
register is 0x61254 bytes after the start of that region.  Both the
whine and brightness are affected by legacy backlight brighness, use (from the same repo as to change it
(the argument is a number from 0 to 255).

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