cr50: improve loader logic to consider build timestamp as well

When deciding which of the two images to start, A or B - consider the
image timestamp if everything else is equal. The later image should
take precedence.

Also, simplify the existing logic, and consider image A to be 'newer'
if both copies are the same otherwise.

BRANCH=none
BUG=chrome-os-partner:37754
TEST=with the rest of the patches applied, verified that the newer
     image of the two gets started

Change-Id: I2c7a50ecfc8d254498c8e96f8651b8d53005897c
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/327414
Reviewed-by: Marius Schilder <mschilder@chromium.org>

1 files changed, 13 insertions, 16 deletions

diff --git a/chip/g/loader/main.c b/chip/g/loader/main.c
index dd538e2c53..985aa34a19 100644
--- a/chip/g/loader/main.c
+++ b/chip/g/loader/main.c
@@ -63,19 +63,16 @@ void panic_printf(const char *format, ...)
 /* Returns 1 if version a is newer, 0 otherwise. */
 int is_newer_than(const struct SignedHeader *a, const struct SignedHeader *b)
 {
-	if (a->epoch_ > b->epoch_)
-		return 1;
-	if (a->epoch_ < b->epoch_)
-		return 0;
-	if (a->major_ > b->major_)
-		return 1;
-	if (a->major_ < b->major_)
-		return 0;
-	if (a->minor_ > b->minor_)
-		return 1;
-	if (a->minor_ < b->minor_)
-		return 0;
-	return 0;
+	if (a->epoch_ != b->epoch_)
+		return a->epoch_ > b->epoch_;
+	if (a->major_ != b->major_)
+		return a->major_ > b->major_;
+	if (a->minor_ != b->minor_)
+		return a->minor_ > b->minor_;
+	if (a->timestamp_ != b->timestamp_)
+		return a->timestamp_ > b->timestamp_;
+
+	return 1; /* All else being equal, consider A to be newer. */
 }
 
 int main(void)
@@ -96,11 +93,11 @@ int main(void)
 	 * Run from bank a if the versions are equal.
 	 */
 	if (is_newer_than(a, b)) {
-		first = b;
-		second = a;
-	} else {
 		first = a;
 		second = b;
+	} else {
+		first = b;
+		second = a;
 	}
 	if (GREG32(PMU, PWRDN_SCRATCH30) == 0xcafebabe) {
 		/* Launch from the alternate bank first.