Change in coreboot[master]: lenovo/x230: introduce FHD variant

[Alexander Couzens (Code Review)]

Alexander Couzens has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/28950 )

Change subject: lenovo/x230: introduce FHD variant
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Patch Set 12:
> Patch Set 12:
> > Patch Set 12:
> > > Patch Set 12:
> > > > Patch Set 12:
> > > > > Patch Set 12:
> > > > >
> > > > > Hi,
> > > > > I was able to build with this patch (using nb51 mod, not Nitrocaster), and it generally works, with following caveats:
> > > > > can't start Windows with libgfxinit - it loads, but as soon as Intel GPU driver is installed the screen goes dark, there's also no output on other connectors
> > > > > display brightness doesn't work out-of-the-box, however there's a utility that takes care of that, so no biggie
> > > > >
> > > > > I can start Windows if I compile with VGA option ROM, VESA framebuffer - which I can set to 1280x1024 (8:8:8) tops, this looks kinda ugly :( Windows will start booting with this resolution, and then switch to FullHD on login screen.
> > > > >
> > > > > I've seen other people have compiled Coreboot with libgfxinit and can start Windows just fine, but all the reports I found were from plain X230, not X330. As far as I understand, libgfxinit uses only data.vbt to initialize GPU. On the other hand, (I might be wrong but) I believe data.vbt is where magic happens to disable LVDS? Or can I use "stock" data.vbt? This is where I'm starting to be lost.
> > > > >
> > > > > Are you able to figure out how to have Windows and FullHD on boot (possibly with libgfxinit)?
> > > >
> > > > libgfxinit does not use data.vbt at all. However, Windows does. Linux can boot without data.vbt as well.
> > >
> > > That's good to know - so essentially the data.vbt here was modify for Windows to use, but Windows doesn't really boot up with provided data.vbt, so I can replace with stock one and not risk being unable to boot into Linux?
> >
> > nb51 mod is different! The brightness of the nb51 is controlled via usb and not via the brightness on board as the nitrocaster does. Can you test if windows boots with the OEM vbt? It would really surprise me, but I don't know the windows IGD driver.
>
> To be frank, I'm not concerned about brightness control at all :-)
>
> I just flashed coreboot with OEM vbt, and surprise! Windows booted, but was thinking it has 2 screens; Linux (Ubuntu 20.04, fully updated) booted, but no output until I started with video=LVDS-0:d video=DP-2:e. Seems that all the secret sauce is indeed in data.vbt provided in this patch, but while Linux is cool with it, Windows isn't.
> How to modify data.vbt? I might do some experiments with it.

I've created https://code.fe80.eu/lynxis/vbtparse to modify the vbt.