Flash pre-init reboots if it needs to clear protection registers

BUG=chrome-os-partner:11171
TEST=manual

1. Clear some of the writable-bits in the flash registers
> ww 0x400fe40c 0xffff1234
write 0x400fe40c = 0xffff1234
> rw 0x400fe40c
read 0x400fe40c = 0xffff1234
2. Reset using power+refresh
3. Register should be clear again
> rw 0x400fe40c
read 0x400fe40c = 0xffffffff
4. Sysinfo should indicate reset-pin reason AND hard-reset reason
> sysinfo
Reset flags: 0x0000000a (reset-pin power-on)
5. Reset using power+refresh
6. Sysinfo should indicate reset-pin reason only
> sysinfo
Reset flags: 0x00000002 (reset-pin)
7. Clear writable-bits again
> ww 0x400fe40c 0xffff1234
write 0x400fe40c = 0xffff1234
8. Jump to another image.  This should NOT trigger a hard reset.
> sysjump A
> sysinfo
Reset flags: 0x00000402 (reset-pin sysjump)

Change-Id: Ie1d6af2acc68217bb82faae464798ee85d63d1ea
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/27540
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/chip/lm4/flash.c b/chip/lm4/flash.c
index 99289b4280..20c90793bd 100644
--- a/chip/lm4/flash.c
+++ b/chip/lm4/flash.c
@@ -7,6 +7,7 @@
 
 #include "flash.h"
 #include "registers.h"
+#include "system.h"
 #include "timer.h"
 #include "util.h"
 #include "watchdog.h"
@@ -180,3 +181,43 @@ void flash_physical_set_protect(int block)
 {
 	LM4_FLASH_FMPPE[F_BANK(block)] &= ~F_BIT(block);
 }
+
+int flash_physical_pre_init(void)
+{
+	int reset_flags = system_get_reset_flags();
+	int any_wp = 0;
+	int i;
+
+	/*
+	 * If we have already jumped between images, an earlier image could
+	 * have applied write protection.  Nothing additional needs to be done.
+	 */
+	if (reset_flags & RESET_FLAG_SYSJUMP)
+		return EC_SUCCESS;
+
+	/* Check if any blocks are currently physically write-protected */
+	for (i = 0; i < (LM4_FLASH_FSIZE + 1) / 32; i++) {
+		if (LM4_FLASH_FMPPE[i] != 0xffffffff) {
+			any_wp = 1;
+			break;
+		}
+	}
+
+	/* If nothing is write-protected, done. */
+	if (!any_wp)
+		return EC_SUCCESS;
+
+	/*
+	 * If the last reboot was a power-on reset, it should have cleared
+	 * write-protect.  If it didn't, then the flash write protect registers
+	 * have been permanently committed and we can't fix that.
+	 */
+	if (reset_flags & RESET_FLAG_POWER_ON)
+		return EC_ERROR_ACCESS_DENIED;
+
+	/* Otherwise, do a hard boot to clear the flash protection registers */
+	system_reset(SYSTEM_RESET_HARD | SYSTEM_RESET_PRESERVE_FLAGS);
+
+	/* That doesn't return, so if we're still here that's an error */
+	return EC_ERROR_UNKNOWN;
+}