Apollo Lake GPIO driver with Coreboot/U-Boot

[Simon Glass]

Hi Wolfgang,

On Thu, 16 Jan 2020 at 02:55, Wolfgang Wallner
<wolfgang.wallner at br-automation.com> wrote:
>
> Hello Simon, Bin, all,
>
> I have an Apollo Lake based device, where U-Boot is booted as a Coreboot
> payload. I would like to utilize the Apollo Lake GPIO driver
> (drivers/gpio/intel_gpio.c), but I struggle with the dependencies.
>
> For my use case, I face 2 obstacles:
>
>   1) Some required drivers are not built
>
>     The Apollo Lake GPIO driver requires the P2SB and ITSS drivers, but those
>     are located in arch/x86/cpu/apollolake. Drivers in this directory are not
>     included in my build as it builds for Coreboot, not for Apollo Lake.
>
>   2) Some header files are not found
>
>     The header files gpio.h and itss.h are located in
>     arch/x86/include/asm/arch-apollolake, but as I build for Coreboot the
>     symlink arch/x86/include/asm/arch points to arch-coreboot instead of
>     arch-apollolake, so those header files are not found.
>
> Does anyone have recommendations on how to solve those issues?
> Would it be possible to move the drivers for P2SB and ITSS out of
> arch/x86/cpu/apollolake to the generic drivers/ directory?

I don't have any great ideas. At present we rely on the device tree to
bind these drivers but I suppose we could add the PCI IDs and then the
coreboot target could bind them.

I did send a series to add checks to skip low-level init as needed
when running from coreboot:

http://patchwork.ozlabs.org/project/uboot/list/?series=149993

>
> regards, Wolfgang
>
> PS: Thanks Simon for providing the initial support for Apollo Lake!

You're welcome. I'm expecting to have full ACPI support around the end
of the month.

Regards,
Simon