chromeec: Add wakeup delay after SPI /CS assertion

Some ECs may require a few microseconds to ramp up their clock after
being awaken by /CS assertion. This adds a Kconfig variable that can
be overridden at the mainboard-level which will force a delay between
asserting /CS and beginning a transfer.

TEST=verified ~100us delay using logic analyzer

Change-Id: I6d9b8beaa808252f008efb10e7448afdf96d2004
Signed-off-by: Stefan Reinauer <>
Original-Commit-Id: ec6b10e4e3f0362dea0dc8046cfd4e4615a42585
Original-Change-Id: Ibba356e4af18f80a7da73c96dadfda0f25251381
Original-Signed-off-by: David Hendricks <>
Original-Reviewed-by: Julius Werner <>
Original-Reviewed-by: Alexandru Stan <>
Reviewed-by: David Hendricks <>
Tested-by: build bot (Jenkins)
2 files changed