drivers/intel/fsp2_0: Add support to identify GPIO config changes

Traditionally, for each Intel platform using FSP, FSP-S has at some
point configured GPIOs differently than the mainboard configuration in
coreboot. This has resulted in various side-effects in coreboot,
payload and OS because of misconfigured GPIOs. On more recent Intel
platforms, a UPD `GpioOverride` is added that coreboot can use to
ensure that FSP does not touch any GPIO configuration.

This change adds a debug option `CHECK_GPIO_CONFIG_CHANGES` to fsp2_0
driver in coreboot that makes a platform callback `gpio_snapshot` to
snapshot GPIO configuration before making a call to FSP SiliconInit
and Notify phases. This snapshot is then compared against the GPIO
configuration using platform callback `gpio_verify_snapshot` after
returning from FSP. The callbacks are not added to romstage (FSP-M)
because mainboard configures all pads in ramstage.

This debug hook allows developers to dump information about any pads
that have a different configuration after call to FSP in ramstage. It
is useful to identify missed UPD configurations or bugs in FSP that
might not honor the UPDs set by coreboot.

This debug hook expects the platform to implement the callbacks
`gpio_snapshot` and `gpio_verify_snapshot`. These can be implemented
as part of the common GPIO driver for platforms using
FSP2.0+. Platforms that implement this support must select the config
`HAVE_GPIO_SNAPSHOT_VERIFY_SUPPORT` to make the debug config
`CHECK_GPIO_CONFIG_CHANGES` visible to user.

Proposal for the GPIO snapshot/verify support was discussed in the RFC
CB:50829.

Signed-off-by: Furquan Shaikh <furquan@google.com>
Change-Id: I5326fc98b6eba0f8ba946842253b288c0d42c523
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50989
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions