[coreboot] Porting Kabylake laptop

[Alex Feinman]

Chris,

The GPIO tables are usually compiled into the BIOS C code and not into ASL. While decompiling DSDT can give you some insight into what GPIOs are used for say WLAN power control or some of the hardware interrupts, there is also a number of Kaby Lake pins that drive system signals or control onboard hardware without going through ASL. For instance Coreboot build for KBL RVP3 uses this:

https://github.com/coreboot/coreboot/blob/master/src/mainboard/intel/kblrvp/variants/rvp3/include/variant/gpio.h


What Niko suggests is to review carefully all the lines that use GPIO_CFG_GPO (output) to ensure that no pins that are configured as output unless you are absolutely sure about where they go. Of course, this requires you to understand the code



________________________________
From: coreboot <coreboot-bounces at coreboot.org> on behalf of chrisglowaki at tutanota.com <chrisglowaki at tutanota.com>
Sent: Monday, June 25, 2018 11:39 AM
To: Coreboot
Subject: Re: [coreboot] Porting Kabylake laptop

On 25. Jun 2018 18:18 nico.h at gmx.de<mailto:nico.h at gmx.de> wrote:

you can generally boot without a complete port. But you can also damage
the hardware if you are not careful. Beside the devicetree settings (pay
attention when it comes to the voltage regulator settings!), the GPIO
configuration should also match your board. You can try to boot without
GPIO configuration (it should be safe because the hardware has to expect
the reset defaults for the GPIOs). But *never* try to boot with a copied
GPIO configuration from another board.


Thank you Nico for the warnings! A few questions:

1. Is it safe to leave default VR settings from Kabylake Reference Board?

2. Can the laptop work properly without GPIO? I don't know if there is a way to dump the GPIO config in vendor firmware on Kabylake.

3. Are there other settings that could damage the hardware?



Regarding the EC, you can learn a lot about its interface from the ven-
dor's ACPI implementation. Unless the board uses a lot of PnP interfaces
of the EC (unlikely for a modern laptop), the datasheet is usually not
helpful. What you really would need is documentation about the EC firm-
ware and its OS interface. And you'll likely not get that.


Can the laptop boot to Linux without EC support in coreboot?

Regarding the ACPI implementation, can that be dumped using acpidump and then used in the ec.asl file?


Thanks,

Chris


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