Support preserving reset flags across a reset

This is needed for flash pre-init to be able to hard reset to clear
uncommitted write protect flags without losing the reset flags.

BUG=chrome-os-partner:11368
TEST=manual

Use reboot and sysinfo commands...

1. reset with keyboard.  flags -> reset-pin
2. 'reboot soft preserve'  flags -> soft reset-pin power-on
3. 'reboot hard preserve'  flags -> hard soft reset-pin power-on
4. 'reboot soft'.  flags -> soft
5. 'reboot hard'.  flags -> hard power-on

Change-Id: I6164a78d99c5c10330f90f651148c5795e7afdda
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/27418

5 files changed, 42 insertions, 20 deletions

diff --git a/chip/lm4/system.c b/chip/lm4/system.c
index 959c3e4232..7b0a3ed041 100644
--- a/chip/lm4/system.c
+++ b/chip/lm4/system.c
@@ -13,8 +13,9 @@
 
 /* Indices for hibernate data registers */
 enum hibdata_index {
-	HIBDATA_INDEX_SCRATCHPAD,  /* General-purpose scratchpad */
-	HIBDATA_INDEX_WAKE,        /* Wake reasons for hibernate */
+	HIBDATA_INDEX_SCRATCHPAD,        /* General-purpose scratchpad */
+	HIBDATA_INDEX_WAKE,              /* Wake reasons for hibernate */
+	HIBDATA_INDEX_SAVED_RESET_FLAGS  /* Saved reset flags */
 };
 
 /* Flags for HIBDATA_INDEX_WAKE */
@@ -135,6 +136,9 @@ static void check_reset_cause(void)
 	if (hib_status & 0x04)
 		flags |= RESET_FLAG_LOW_BATTERY;
 
+	/* Restore then clear saved reset flags */
+	flags |= hibdata_read(HIBDATA_INDEX_SAVED_RESET_FLAGS);
+	hibdata_write(HIBDATA_INDEX_SAVED_RESET_FLAGS, 0);
 
 	system_set_reset_flags(flags);
 }
@@ -247,18 +251,23 @@ int system_pre_init(void)
 	return EC_SUCCESS;
 }
 
-void system_reset(int is_hard)
+void system_reset(int flags)
 {
 	/* Disable interrupts to avoid task swaps during reboot */
 	interrupt_disable();
 
-	if (is_hard) {
+	/* Save current reset reasons if necessary */
+	if (flags & SYSTEM_RESET_PRESERVE_FLAGS)
+		hibdata_write(HIBDATA_INDEX_SAVED_RESET_FLAGS,
+			      system_get_reset_flags());
+	else
+		hibdata_write(HIBDATA_INDEX_SAVED_RESET_FLAGS, 0);
+
+	if (flags & SYSTEM_RESET_HARD) {
 		/* Bounce through hibernate to trigger a hard reboot */
 		hibernate(0, 50000, HIBDATA_WAKE_HARD_RESET);
-	} else {
-		/* Soft reboot */
+	} else
 		CPU_NVIC_APINT = 0x05fa0004;
-	}
 
 	/* Spin and wait for reboot; should never return */
 	while (1)
diff --git a/chip/stm32/system.c b/chip/stm32/system.c
index 8f72fb04b5..4222bfefea 100644
--- a/chip/stm32/system.c
+++ b/chip/stm32/system.c
@@ -86,13 +86,13 @@ int system_pre_init(void)
 }
 
 
-void system_reset(int is_hard)
+void system_reset(int flags)
 {
 	/* Disable interrupts to avoid task swaps during reboot */
 	interrupt_disable();
 
 	/* TODO: (crosbug.com/p/7470) support hard boot; this is a
-	 * soft boot. */
+	 * soft boot.  And support preserving reset flags, too... */
 	CPU_NVIC_APINT = 0x05fa0004;
 
 	/* Spin and wait for reboot; should never return */
diff --git a/common/host_command.c b/common/host_command.c
index 158aa79726..1420e79434 100644
--- a/common/host_command.c
+++ b/common/host_command.c
@@ -47,7 +47,7 @@ void host_command_received(struct host_cmd_handler_args *args)
 	 * other command.
 	 */
 	if (args->command == EC_CMD_REBOOT) {
-		system_reset(1);
+		system_reset(SYSTEM_RESET_HARD);
 		/* Reset should never return; if it does, post an error */
 		host_send_response(EC_RES_ERROR);
 		return;
diff --git a/common/system_common.c b/common/system_common.c
index 87685abc40..680d0c90ed 100644
--- a/common/system_common.c
+++ b/common/system_common.c
@@ -519,7 +519,7 @@ static int handle_pending_reboot(enum ec_reboot_cmd cmd)
 	case EC_REBOOT_JUMP_RW_B:
 		return system_run_image_copy(SYSTEM_IMAGE_RW_B);
 	case EC_REBOOT_COLD:
-		system_reset(1);
+		system_reset(SYSTEM_RESET_HARD);
 		/* That shouldn't return... */
 		return EC_ERROR_UNKNOWN;
 	case EC_REBOOT_DISABLE_JUMP:
@@ -676,24 +676,28 @@ DECLARE_CONSOLE_COMMAND(sysjump, command_sysjump,
 
 static int command_reboot(int argc, char **argv)
 {
-	int is_hard = 0;
+	int flags = 0;
 
-	if (argc == 2) {
+	if (argc >= 2) {
 		if (!strcasecmp(argv[1], "hard") ||
 		    !strcasecmp(argv[1], "cold")) {
 			ccputs("Hard-");
-			is_hard = 1;
+			flags |= SYSTEM_RESET_HARD;
+		} else if (!strcasecmp(argv[1], "soft")) {
+			/* No extra flags */
 		} else
 			return EC_ERROR_PARAM1;
 	}
+	if (argc >= 3 && !strcasecmp(argv[2], "preserve"))
+		flags |= SYSTEM_RESET_PRESERVE_FLAGS;
 
 	ccputs("Rebooting!\n\n\n");
 	cflush();
-	system_reset(is_hard);
+	system_reset(flags);
 	return EC_SUCCESS;
 }
 DECLARE_CONSOLE_COMMAND(reboot, command_reboot,
-			"[hard]",
+			"[hard|soft] [preserve]",
 			"Reboot the EC",
 			NULL);
 
diff --git a/include/system.h b/include/system.h
index ba046cc1b6..02dc2ce2bb 100644
--- a/include/system.h
+++ b/include/system.h
@@ -124,10 +124,19 @@ int system_get_board_version(void);
  * user/machine which performed the build. */
 const char *system_get_build_info(void);
 
-/* Reset the system.  If is_hard, performs a hard reset, which cuts power to
- * the entire system; else performs a soft reset (which resets the core and
- * on-chip peripherals, without actually cutting power to the chip). */
-void system_reset(int is_hard);
+/* Flags for system_reset() */
+/*
+ * Hard reset.  Cuts power to the entire system.  If not present, does a soft
+ * reset which just resets the core and on-chip peripherals.
+ */
+#define SYSTEM_RESET_HARD           (1 << 0)
+/*
+ * Preserve existing reset flags.  Used by flash pre-init when it discovers it
+ * needs to do a hard reset to clear write protect registers.
+ */
+#define SYSTEM_RESET_PRESERVE_FLAGS (1 << 1)
+
+void system_reset(int flags);
 
 /* Set a scratchpad register to the specified value.  The scratchpad
  * register must maintain its contents across a software-requested