stm32: Store VbNvContext in backup registers

This would improve boot speed when compared to storing in eMMC because
initialing eMMC is slow.

So far other platforms do not have this need because CMOS is quite
efficient; thus it is left unimplemented in lm4.

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>

BRANCH=snow
BUG=chrome-os-partner:10660,13094
TEST=On Snow, see VbNvContext is preserved across power cycles (you have
     to patch U-Boot to test this)

Change-Id: If5072c678b87bc47a3a82a1dff2afa3896304f36
Reviewed-on: https://gerrit.chromium.org/gerrit/31832
Tested-by: Che-Liang Chiou <clchiou@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Che-Liang Chiou <clchiou@chromium.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/chip/lm4/system.c b/chip/lm4/system.c
index 6046f15d4c..2c970ee125 100644
--- a/chip/lm4/system.c
+++ b/chip/lm4/system.c
@@ -396,6 +396,16 @@ const char *system_get_chip_name(void)
 	}
 }
 
+int system_get_vbnvcontext(uint8_t *block)
+{
+	return EC_ERROR_UNIMPLEMENTED;
+}
+
+int system_set_vbnvcontext(const uint8_t *block)
+{
+	return EC_ERROR_UNIMPLEMENTED;
+}
+
 const char *system_get_chip_revision(void)
 {
 	static char rev[3];