cr50: add a closed loop reset function

Add a function that asserts EC_RST_L until TPM_RST_L gets asserted.
Disable sleep using SLEEP_MASK_AP_RUN while waiting for the AP reset.
Disable tpm communications using tpm_stop until the AP is reset.

BUG=b:123544145
BRANCH=cr50
TEST=run 'ecrst cl' on mistral, scarlet, and soraka. Make sure the
sleepmask is cleared correctly and the TPM works after the reset is
complete.

Change-Id: I5971b45b7a69fd24887a7c22ee7984972b7828ae
Signed-off-by: Mary Ruthven <mruthven@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1444411
Commit-Ready: Mary Ruthven <mruthven@chromium.org>
Tested-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Keith Short <keithshort@chromium.org>

1 files changed, 31 insertions, 3 deletions

diff --git a/board/cr50/ap_state.c b/board/cr50/ap_state.c
index 32064ae07c..7e7d1231d2 100644
--- a/board/cr50/ap_state.c
+++ b/board/cr50/ap_state.c
@@ -4,12 +4,11 @@
  *
  * AP state machine
  */
-#include "ccd_config.h"
-#include "common.h"
-#include "console.h"
 #include "gpio.h"
 #include "hooks.h"
+#include "registers.h"
 #include "system.h"
+#include "tpm_registers.h"
 
 #define CPRINTS(format, args...) cprints(CC_SYSTEM, format, ## args)
 
@@ -101,6 +100,7 @@ void set_ap_on(void)
 		disable_deep_sleep();
 }
 
+static uint8_t waiting_for_ap_reset;
 /*
  * If TPM_RST_L is asserted, the AP is in reset. Disable all AP functionality
  * in 1 second if it remains asserted.
@@ -117,6 +117,34 @@ void tpm_rst_asserted(enum gpio_signal unused)
 	hook_call_deferred(&deferred_set_ap_off_data, SECOND);
 
 	set_state(DEVICE_STATE_DEBOUNCING);
+
+	if (waiting_for_ap_reset) {
+		waiting_for_ap_reset = 0;
+		deassert_ec_rst();
+		enable_sleep(SLEEP_MASK_AP_RUN);
+	}
+}
+
+void board_closed_loop_reset(void)
+{
+	/* Disable sleep while waiting for the reset */
+	disable_sleep(SLEEP_MASK_AP_RUN);
+
+	waiting_for_ap_reset = 1;
+
+	/* Disable AP communications with the TPM until cr50 sees the reset */
+	tpm_stop();
+
+	/* Use EC_RST_L to reset the system */
+	assert_ec_rst();
+
+	/*
+	 * DETECT_TPM_RST_L_ASSERTED is edge triggered. If TPM_RST_L is already
+	 * low, tpm_rst_asserted wont get called. Alert tpm_rst_asserted
+	 * manually if the signal is already low.
+	 */
+	if (!gpio_get_level(GPIO_DETECT_TPM_RST_L_ASSERTED))
+		tpm_rst_asserted(GPIO_TPM_RST_L);
 }
 
 /**