[coreboot] Intel native graphics init: Questions about GTT setup

[Anthony Martin]

Paul Menzel <paulepanter at users.sourceforge.net> once said:
> since Linux 3.12+ graphics stolen memory seems to be used, which causes
> a regression with coreboot and native graphics init at least on the
> Intel 945 based Lenovo X60 [1].
> 
> This seems to be solved by properly setting register `PGETBL_CTL` [2],
> but the Linux kernel Intel graphics driver still reports a GTT (Graphics
> Translation Table) related error during start-up, but everything else
> seems to work.
> 
>         [    1.235640] [drm] GPU crash dump saved to /sys/class/drm/card0/error
>         [    1.236583] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
>         [    1.236583] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
>         [    1.236583] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
>         [    1.236583] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
>         [    1.236583] i915: render error detected, EIR: 0x00000010
>         [    1.236583] i915: page table error
>         [    1.236583] i915:   PGTBL_ER: 0x00000013
>         [    1.236583] [drm:i915_report_and_clear_eir] *ERROR* EIR stuck: 0x00000010, masking
>         [    1.236583] i915: render error detected, EIR: 0x00000010
>         [    1.236583] i915: page table error
>         [    1.236583] i915:   PGTBL_ER: 0x00000013
> 

FWIW, I will occasionally get the same message and the apparent
working behavior after resume on a MacBook2,1 using stock Apple
EFI firmware. The MacBook uses the same chipset as the X60.

[49087.421096] [drm] GPU crash dump saved to /sys/class/drm/card0/error
[49087.421096] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
[49087.421097] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
[49087.421097] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
[49087.421098] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
[49087.421763] i915: render error detected, EIR: 0x00000010
[49087.421763] i915: page table error
[49087.421763] i915:   PGTBL_ER: 0x00000001
[49087.421763] [drm:i915_report_and_clear_eir] *ERROR* EIR stuck: 0x00000010, masking
[49087.421763] i915: render error detected, EIR: 0x00000010
[49087.421763] i915: page table error
[49087.421763] i915:   PGTBL_ER: 0x00000001

  Anthony