mainboard/google/volteer: Disable S0i3.4 if cr50 firmware is too old

For Volteer (and future Tiger Lake boards) we can enable mode S0i3.4
only if we know that the Cr50 is generating 100us interrupt pulses.
We have to do so, because the SoC is not guaranteed to detect pulses
shorter than 100us in S0i3.4 substate.

A new Kconfig setting CR50_USE_LONG_INTERRUPT_PULSES controls new code
running in verstage, which will program a new Cr50 register, provided
that Cr50 firmware is new enough to support the register.

This CL adds code to detect the case when Cr50 is unable to generate
longer pulses, and in that case explicitly disable the S0i3.4 substate
as well as setting gpio_pm_override to all zeroes.  This will increase
power usage slightly, but guarantee that the GPIO block in the SoC
does not switch to a slower sampling clock.  In practice, this case
will only be encountered in the factory, before the Cr50 chip is
updated to a new RW image.

(Prior to this change, the gpio_pm_override was hardcoded to zero for
Volteer, but the S0i3.4 substate was not disabled.  According to my
conversations with Intel engineers, that was not enough to guarantee
detection pulses shorter than 100us.  But it is entirely possible that
we have just been "lucky" that the SoC has not gone into low power
mode during the boot process, where most of the cr50 communication
happens.)

TEST=util/abuild/abuild -t GOOGLE_VOLTEER -c max -x
BUG=b:154333137

Change-Id: Idef1fffd410a345678da4b3c8aea46ac74a01470
Signed-off-by: Jes Bodi Klinke <jbk@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44359
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

0 files changed, 0 insertions, 0 deletions