cr50: try recovering from rolling rebootsstabilize-8688.B

Sometimes a perfectly sane image enters rolling reboot mode in case
some data change triggered a bug which prevents the normal startup and
causes a reset.

The most likely task causing in in case of cr50 would be the tpm task.

Let's add another check of the restart counter: should it reach the
value of 50, do not start the TPM task.

BRANCH=none
BUG=chrome-os-partner:55708

TEST=with this code plus an unaligned access introduced in tpm
     initialization sequence in both RW_A and RW_B, program the full
     image on the dev board.

     Observe the device reset 50 time is rapid succession and then
     stop with the following message on the console:

  Bldr |511709
  retry|50
  Himg =4F992103..408D193E
  Hfss =384E4655..EE13EBD0
  Hinf =44D21600..B70529BD
  jump @00044000

  --- UART initialized after reboot ---
  [Reset cause: rtc-alarm]
  [Image: RW, cr50_v1.1.5044-8d6f7a2+ private-cr51:v0.0.68-633229c ...
  + cryptoc:v0.0.4-5319e83 2016-08-07 19:37:16 vbendeb@kvasha]
  [0.004130 Inits done]
  [0.006919 Active NVram partition set to 0]
  Console is enabled; type HELP for help.
  > system_rolling_reboot_suspected: roling reboots suspected. Try \
   powercycling to clear
   this condition.
  [0.010502 Task 2 (TPM) exited!]

Change-Id: I6b08c5c1a02da9edf9bdf394e57cc56d2e595ad1
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/366892
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

3 files changed, 27 insertions, 0 deletions

diff --git a/chip/g/system.c b/chip/g/system.c
index 9bc3a26b8e..461f05a462 100644
--- a/chip/g/system.c
+++ b/chip/g/system.c
@@ -353,6 +353,22 @@ int system_process_retry_counter(void)
 	 */
 	return corrupt_other_header(other);
 }
+
+int system_rolling_reboot_suspected(void)
+{
+	if (GREG32(PMU, LONG_LIFE_SCRATCH0) > 50) {
+		/*
+		 * The chip has restarted 50 times without the restart counter
+		 * cleared. There must be something wrong going, the chip is
+		 * likely in rolling reboot.
+		 */
+		ccprintf("%s: Try powercycling to clear this condition.\n",
+			 __func__);
+		return 1;
+	}
+
+	return 0;
+}
 #endif
 
 uint32_t system_get_board_properties(void)
diff --git a/common/tpm_registers.c b/common/tpm_registers.c
index 94b1636b0a..6811c1d758 100644
--- a/common/tpm_registers.c
+++ b/common/tpm_registers.c
@@ -571,6 +571,9 @@ static void call_extension_command(struct tpm_cmd_header *tpmh,
 
 void tpm_task(void)
 {
+	if (system_rolling_reboot_suspected())
+		return;
+
 	tpm_init();
 	sps_tpm_enable();
 	while (1) {
diff --git a/include/system.h b/include/system.h
index 1c04ee3404..7b08683ac0 100644
--- a/include/system.h
+++ b/include/system.h
@@ -489,4 +489,12 @@ uint32_t system_get_board_properties(void);
  */
 uint32_t system_board_properties_callback(void);
 
+/**
+ * A function provided by some platforms to hint that something is going
+ * wrong.
+ *
+ * @return a boolean, set to True if rolling reboot condition is suspected.
+ */
+int system_rolling_reboot_suspected(void);
+
 #endif  /* __CROS_EC_SYSTEM_H */