[coreboot] HV121WX4-120 screen for X200

Merlin Büge toni at bluenox07.de
Sat Aug 11 13:48:02 CEST 2018


I also have that panel in my X200 and it's working fine here. Don't
remember if it worked with stock BIOS, but the latest libreboot release
(20160907) is working fine. I will also try latest coreboot in the next
weeks, and will report back if I experience strange behaviour.

For now it works quite stable (compared to what I've heard), I get
random hangs about 10 times a year with nearly constant uptime.

I also replaced the panel's CCFL with an LED stripe and therefore have
a modified version of the LED board (where the CCFL inverter was
located), but I'm very sure the panel worked fine before that



On Sat, 11 Aug 2018 00:34:35 +0200
Piotr Kubaj via coreboot <coreboot at coreboot.org> wrote:

> Hi,
> I just wanted to share my experience of using alternative screens for
> ThinkPad X200 (HV121WX4-120) with coreboot.
> After fitting the screen, it became apparent that something is wrong.
> Having turned on the X200, it ran happily for about 1 minute, then
> the screen just powered off. It didn't matter whether I stayed in
> SeaBIOS, or just booted my OS. And when the screen powered off, I
> could awake it after several minutes, but only for another minute.
> Apart from that, the laptop worked.
> nico_h from IRC helped me (thank you!) by providing alternative
> values for devicetree, which could make the screen work orderly.
> Well, it did work better, but still wasn't stable (it worked for
> 10-20 minutes, once I even got it to 2 hours).
> Still, that was a huge difference. I tried to experiment a little
> with it and set some crazy values: register
> "gpu_panel_power_up_delay" = "600"             # T1+T2: 25ms register
> "gpu_panel_power_down_delay" = "3000"          # T3:    25ms register
> "gpu_panel_power_backlight_on_delay" = "500"   # T5:   250ms register
> "gpu_panel_power_backlight_off_delay" = "2500" # Tx:   250ms register
> "gpu_panel_power_cycle_delay" = "255"          # T4:   200ms
> After that, things seem to work fine.
> I hope someone finds it useful if they replace their X200's screen
> with alternative one.
> Again thanks to Nico for help!

Merlin Büge

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