[M] Change in coreboot[master]: mb/google/poppy: Nami - invoke power cycle of FPMCU on startup

[Tarun Tuli (Code Review)]

Attention is currently required from: Martin L Roth.

Hello Shelley Chen, build bot (Jenkins), Subrata Banik,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/68820

to look at the new patch set (#24).

Change subject: mb/google/poppy: Nami - invoke power cycle of FPMCU on startup
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mb/google/poppy: Nami - invoke power cycle of FPMCU on startup

Add functionality such that the FPMCU is power cycled long enough
on boot to ensure proper reset.

This solution relies solely on coreboot to sequence the power and reset
signals appropriately.  With kernel control, we are getting into
undetermined states on the FPMCU that have not been fully root caused.

BUG=b:245954151
TEST=Confirmed FPMCU is still functional on Nami.
Confirmed power is off for 150ms seconds on boot.
Confirmed RCC_CSR of FPMCU indicates power cycle occurred.
Confirmed reset is de-asserted approx 3ms after power application
(target >2.5ms)

Change-Id: I21eb85dc11e0ea0eb5de8a6092b01663d3c3df91
Signed-off-by: Tarun Tuli 
---
M src/mainboard/google/poppy/variants/nami/gpio.c
M src/mainboard/google/poppy/variants/nami/mainboard.c
2 files changed, 99 insertions(+), 4 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/20/68820/24