[XS] Change in coreboot[main]: mb/google/brya: Correct Ti50 EC-is-trusted logic

[Subrata Banik (Code Review)]

Subrata Banik has submitted this change. ( https://review.coreboot.org/c/coreboot/+/80158?usp=email )

Change subject: mb/google/brya: Correct Ti50 EC-is-trusted logic
......................................................................

mb/google/brya: Correct Ti50 EC-is-trusted logic

With Cr50, the GPIO EC_IN_RW is used to determine whether EC is trusted. However, With the switch to Ti50, it is determined by Ti50's boot mode. If the boot mode is TRUSTED_RO, the VB2_CONTEXT_EC_TRUSTED flag will be set in check_boot_mode(). Therefore in the Ti50 case get_ec_is_trusted() can just return 0.

The current code of get_ec_is_trusted() only checks the GPIO, which
causes the EC to be always considered "trusted". Therefore, correct the return value to 0 for TPM_GOOGLE_TI50.

BUG=b:321172119
TEST=emerge-nissa coreboot chromeos-bootimage
TEST=firmware_DevMode passed in FAFT test

Change-Id: I308f8b36411030911c4421d80827fc49ff325a1b
Signed-off-by: Qinghong Zeng <[e-mail]- partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80158
Tested-by: build bot (Jenkins) 
Reviewed-by: Subrata Banik 
Reviewed-by: Yu-Ping Wu 
Reviewed-by: Tyler Wang 
Reviewed-by: Ian Feng 
Reviewed-by: Weimin Wu 
Reviewed-by: Eric Lai 
---
M src/mainboard/google/brya/chromeos.c
1 file changed, 4 insertions(+), 0 deletions(-)

Approvals:
  Weimin Wu: Looks good to me, but someone else must approve
  Yu-Ping Wu: Looks good to me, approved
  Eric Lai: Looks good to me, approved
  Subrata Banik: Looks good to me, approved
  Ian Feng: Looks good to me, but someone else must approve
  Tyler Wang: Looks good to me, but someone else must approve
  build bot (Jenkins): Verified

diff --git a/src/mainboard/google/brya/chromeos.c b/src/mainboard/google/brya/chromeos.c
index 5c99371..73b7237 100644
--- a/src/mainboard/google/brya/chromeos.c
+++ b/src/mainboard/google/brya/chromeos.c
@@ -24,6 +24,10 @@

int get_ec_is_trusted(void)
 {
+	/* With Ti50, VB2_CONTEXT_EC_TRUSTED should be set according to the boot mode. */
+	if (CONFIG(TPM_GOOGLE_TI50))
+		return 0;
+
    /* EC is trusted if not in RW. */
    return !gpio_get(GPIO_EC_IN_RW);
 }