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

[Michał Masłowski]

> 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
> intel_regs.py 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
i945-backlight.py (from the same repo as intel-regs.py) to change it
(the argument is a number from 0 to 255).

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