cr50: Preserve CCD state across deep sleep

Define two bits in a long-life register to hold the current CCD state
across deep sleep.  Update the bits on CCD config change, and restore
them on init.

This is necessary because Cr50 loses RAM contents on deep sleep.  It
would be really inconvenient to open CCD, get a cup of coffee, and
come back to find CCD has locked again because Cr50 was idle too long.

See go/cr50-ccd-wp for more information.

BUG=b:62537474
BRANCH=cr50
TEST=manual with CR50_DEV=1 build
     ccdinfo --> state=opened
     idle d
     ccdunlock
     ccdinfo --> state=unlocked
     (wait for deep sleep)
     sysinfo --> reset flags = hibernate wake-pin
     ccdinfo --> state=unlocked
     reboot
     sysinfo --> reset flags = hard
     ccdinfo --> state=opened

Change-Id: I7864f374af5c159bc9691b094958fb030f3cb8ad
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/575996
Reviewed-by: Mary Ruthven <mruthven@chromium.org>

2 files changed, 41 insertions, 1 deletions

diff --git a/board/cr50/board.c b/board/cr50/board.c
index f3e3f59dcf..76b14b1f30 100644
--- a/board/cr50/board.c
+++ b/board/cr50/board.c
@@ -618,6 +618,12 @@ static void  check_board_id_mismatch(void)
 /* Initialize board. */
 static void board_init(void)
 {
+#ifdef CR50_DEV
+	static enum ccd_state ccd_init_state = CCD_STATE_OPENED;
+#else
+	static enum ccd_state ccd_init_state = CCD_STATE_LOCKED;
+#endif
+
 	/*
 	 * Deep sleep resets should be considered valid and should not impact
 	 * the rolling reboot count.
@@ -634,8 +640,19 @@ static void board_init(void)
 	nvmem_init();
 	/* Initialize the persistent storage. */
 	initvars();
+
+	/*
+	 * If this was a low power wake and not a rollback, restore the ccd
+	 * state from the long-life register.
+	 */
+	if ((system_get_reset_flags() & RESET_FLAG_HIBERNATE) &&
+	    !system_rollback_detected()) {
+		ccd_init_state = (GREG32(PMU, LONG_LIFE_SCRATCH1) &
+				  BOARD_CCD_STATE) >> BOARD_CCD_SHIFT;
+	}
+
 	/* Load case-closed debugging config */
-	ccd_config_init();
+	ccd_config_init(ccd_init_state);
 
 	system_update_rollback_mask_with_both_imgs();
 
@@ -661,6 +678,20 @@ static void board_init(void)
 }
 DECLARE_HOOK(HOOK_INIT, board_init, HOOK_PRIO_DEFAULT);
 
+/**
+ * Hook for CCD config loaded/changed.
+ */
+static void board_ccd_config_changed(void)
+{
+	/* Store the current CCD state so we can restore it after deep sleep */
+	GWRITE_FIELD(PMU, LONG_LIFE_SCRATCH_WR_EN, REG1, 1);
+	GREG32(PMU, LONG_LIFE_SCRATCH1) &= ~BOARD_CCD_STATE;
+	GREG32(PMU, LONG_LIFE_SCRATCH1) |= (ccd_get_state() << BOARD_CCD_SHIFT)
+			& BOARD_CCD_STATE;
+	GWRITE_FIELD(PMU, LONG_LIFE_SCRATCH_WR_EN, REG1, 0);
+}
+DECLARE_HOOK(HOOK_CCD_CHANGE, board_ccd_config_changed, HOOK_PRIO_DEFAULT);
+
 #if defined(CONFIG_USB)
 const void * const usb_strings[] = {
 	[USB_STR_DESC] = usb_string_desc,
diff --git a/board/cr50/scratch_reg1.h b/board/cr50/scratch_reg1.h
index 546cd43d62..23b03db546 100644
--- a/board/cr50/scratch_reg1.h
+++ b/board/cr50/scratch_reg1.h
@@ -38,6 +38,15 @@
 #define BOARD_NO_RO_UART             (1 << 10)
 
 /*
+ * Bits to store current case-closed debug state across deep sleep.
+ *
+ * DO NOT examine these bits to determine the current CCD state.  Call methods
+ * from case_closed_debug.h instead.
+ */
+#define BOARD_CCD_SHIFT              11
+#define BOARD_CCD_STATE              (3 << BOARD_CCD_SHIFT)
+
+/*
  * Macro to capture all properties related to board strapping pins. This must be
  * updated if additional strap related properties are added.
  */