Make flash_ec capable of writing to an incorrectly-protected STM32

If EC-RO protects itself via the WRPx option bytes, flash_ec will fail
to reprogram it.  And if EC-RO is broken/unbootable, it won't be able
to clear the WRPx option bytes itself when it sees the write protect
GPIO is not asserted.

Add the -u flag to stm32mon so that it will automatically attempt to
unprotect the flash via the option bytes.

BUG=chrome-os-partner:19723
BRANCH=none
TEST=enable write protect GPIO.  Then from console, 'flashwp enable'.
     Then from the chroot:
        ./util/flash_ec --board=pit --ro --image=build/pit/ec.RO.flat
     That should successfully reflash the board.

Change-Id: Ic356d29104294d04d5e2a36dc75fd0206b89bd34
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/56659

1 files changed, 6 insertions, 8 deletions

diff --git a/util/flash_ec b/util/flash_ec
index 32301315f0..4ee207dfd1 100755
--- a/util/flash_ec
+++ b/util/flash_ec
@@ -152,8 +152,8 @@ function flash_daisy() {
 	fi
 
 	if [ "${FLAGS_unprotect}" = ${FLAGS_TRUE} ] ; then
-		# Unprotect exists, but isn't needed because it's implicit
-		# in writing the entire image
+		# Unprotect exists, but isn't needed because erasing pstate is
+		# implicit in writing the entire image
 		die "--unprotect not supported for this board."
 	fi
 
@@ -169,10 +169,8 @@ function flash_daisy() {
 	ec_enable_boot0
 	# Reset the EC
 	ec_reset
-	# TODO: add -u flag to unprotect the flash so that writes will succeed
-	# on a chip which has temporarily protected itself via the WRPx option
-	# bytes.
-	${STM32MON} -d ${EC_UART} -e -w ${IMG}
+	# Unprotect flash, erase, and write
+	${STM32MON} -d ${EC_UART} -u -e -w ${IMG}
 }
 
 function flash_link() {
@@ -197,8 +195,8 @@ function flash_slippy() {
 	OCD_PATH="${SRC_ROOT}/platform/ec/chip/lm4/openocd"
 	OCD_CMDS="init; flash_lm4 ${IMG} ${FLAGS_offset};"
 	if [ "${FLAGS_unprotect}" = ${FLAGS_TRUE} ] ; then
-		# Unprotect exists, but isn't needed because it's implicit
-		# in writing the entire image
+		# Unprotect exists, but isn't needed because erasing pstate is
+		# implicit in writing the entire image
 		die "--unprotect not supported for this board."
 	fi
 	OCD_CMDS="${OCD_CMDS} shutdown;"