cr50: add support for enabling terminations on ap suspend

rk3399 systems need terminations on the SPI signals in S3 and all other
low power states. Add support for enabling the pulldowns and pullups on
the correct pins.

With this change, if BOARD_NEEDS_S3_TERM is set in the board properties,
cr50 will enable a pulldown on the AP TX Cr50 RX signal and a pulldown
on all of the SPS signals. To keep the pulldowns from interfering with
the sps peripheral, s3_term will also disable the input for those
signals.

BUG=b:62200096
BRANCH=cr50
TEST=Flash onto bob. Make sure cr50 enables and disables terminations
when the AP suspends/resumes. Flash onto reef. Make sure it doesn't do
anything.

Change-Id: I4adaf6d66160bab1eb3cf3d343d4a79524ccf883
Signed-off-by: Mary Ruthven <mruthven@google.com>
Reviewed-on: https://chromium-review.googlesource.com/991338
Commit-Ready: Mary Ruthven <mruthven@chromium.org>
Tested-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/board/cr50/build.mk b/board/cr50/build.mk
index 049e29eafc..c245920bcd 100644
--- a/board/cr50/build.mk
+++ b/board/cr50/build.mk
@@ -39,6 +39,7 @@ board-${CONFIG_RDD} += rdd.o
 board-${CONFIG_USB_SPI} += usb_spi.o
 board-${CONFIG_USB_I2C} += usb_i2c.o
 board-y += recovery_button.o
+board-y += s3_term.o
 board-y += tpm2/NVMem.o
 board-y += tpm2/aes.o
 board-y += tpm2/ecc.o