cr50: provide means of posting reboot request

Usually CR50 TPM reset happens when the AP reboots, the CR50 RO does
not get a chance to run in this case, so the running RW does not
change either,

Once the idle RW section was updated, the only way to start it is to
reboot the CR50 completely, Rebooting CR50 causes the whole system
reset, so it should not be happening at random moments in time.

This patch introduces a mechanism to delay reboot to the moment when
the TPM is reset. The reboot request would be posted in the end of the
update, and then the AP would reboot, triggering a TPM reboot, which
in turn would trigger the CR50 reset.

The USB update handler now posts the reboot request instead of
triggering the reboot immediately.

BRANCH=none
BUG=chrome-os-partner:58226
TEST=with the rest of the patches applied verified that the system
     gets reset and the new image version kicks in on both gru (over
     SPI) and reef (over USB).

Change-Id: Iff859f2e7a48c5035a27fffd17aefe7e318af569
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/395627
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

board/cr50/board.c

@@ -71,7 +71,13 @@ uint32_t nvmem_user_sizes[NVMEM_NUM_USERS] = {
 
 /*  Board specific configuration settings */
 static uint32_t board_properties;
+static uint8_t reboot_request_posted;
 
+void post_reboot_request(void)
+{
+	/* Reboot the device next time TPM reset is requested. */
+	reboot_request_posted = 1;
+}
 /*
  * There's no way to trigger on both rising and falling edges, so force a
  * compiler error if we try. The workaround is to use the pinmux to connect
@@ -378,6 +384,9 @@ void sys_rst_asserted(enum gpio_signal signal)
 		return;
 	}
 
+	if (reboot_request_posted)
+		system_reset(SYSTEM_RESET_HARD);  /* This will never return. */
+
 	/* Re-initialize the TPM software state */
 	tpm_reset();
 }

board/cr50/board.h

@@ -139,6 +139,7 @@ void board_configure_deep_sleep_wakepins(void);
 /* Interrupt handler */
 void sys_rst_asserted(enum gpio_signal signal);
 void device_state_on(enum gpio_signal signal);
+void post_reboot_request(void);
 
 /* Special controls over EC and AP */
 void assert_sys_rst(void);

chip/g/usb_upgrade.c

@@ -182,14 +182,12 @@ static void upgrade_out_handler(struct consumer const *consumer, size_t count)
 
 	if (rx_state_ == rx_awaiting_reset) {
 		/*
-		 * Any USB data received in this state triggers reset, no
+		 * Any USB data received in this state should cause a post of
+		 * a system reset request on the next TPM reboot, no USB
 		 * response required.
 		 */
-		CPRINTS("reboot hard");
-		cflush();
-		system_reset(SYSTEM_RESET_HARD);
-		while (1)
-			;
+		rx_state_ = rx_idle;
+		post_reboot_request();
 	}
 
 	if (rx_state_ == rx_outside_block) {