flash_fp_mcu: Add FPMCU power cycle

This is a workaround for the dartmonkey RO flash init bug,
where a boot loop occurs when HW-WP is disabled, but SW-WP
is still enabled.

We force a true power-on-reset so that flash init function in RO
sees that SW-WP cannot be removed (and is "stuck").

BRANCH=none
BUG=b:146428434,b:187387061,b:143374692
TEST=# Test on helios, bard, and nocturne
     scp util/flash_fp_mcu ${DUT_HOSTNAME}:/usr/local/bin/flash_fp_mcu
     ssh ${DUT_HOSTNAME} ectool --name=cros_fp reboot_ec
     ssh ${DUT_HOSTNAME} ectool --name=cros_fp uptimeinfo
     # No power-on reset flag should be set.
     ssh ${DUT_HOSTNAME} flash_fp_mcu
     # Check that power-on reset flag is set.
     # If you were to check the uptimeinfo after flash_fp_mu
     # finished, you would see a few seconds later that the
     # power-on flag is gone. This is because biod's startup
     # would reinitialize entropy and cause reset.
TEST=# Test on morphius
     scp util/flash_fp_mcu ${DUT_HOSTNAME}:/usr/local/bin/flash_fp_mcu
     ssh ${DUT_HOSTNAME} flash_fp_mcu
     # Just make sure we didn't break the script.

Signed-off-by: Craig Hesling <hesling@chromium.org>
Change-Id: Ib8e239c6c0d5e5de66da2e664374a80479eb4098
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3032665
Commit-Queue: Josie Nordrum <josienordrum@google.com>
Reviewed-by: Josie Nordrum <josienordrum@google.com>

1 files changed, 19 insertions, 3 deletions

diff --git a/util/flash_fp_mcu b/util/flash_fp_mcu
index 2b2e31918f..94551c5741 100644
--- a/util/flash_fp_mcu
+++ b/util/flash_fp_mcu
@@ -414,11 +414,26 @@ flash_fp_mcu_stm32() {
   fi
   gpio unexport "${gpio_boot0}" "${gpio_nrst}"
 
-  # wait for FP MCU to come back up (including RWSIG delay)
-  sleep 2
+  # Dartmonkey's RO has a flashprotect logic issue that forces reboot loops
+  # when SW-WP is enabled and HW-WP is disabled. It is avoided if a POR is
+  # detected on boot. We force a POR here to ensure we avoid this reboot loop.
+  # See to b/146428434.
+  if [[ "${gpio_pwren}" -gt 0 ]]; then
+    echo "Power cycling the FPMCU."
+    gpio export "${gpio_pwren}"
+    gpio out    "${gpio_pwren}"
+    gpio 0      "${gpio_pwren}"
+    # Must outlast hardware soft start, which is typically ~3ms.
+    sleep 0.5
+    gpio 1      "${gpio_pwren}"
+    # Power enable line is externally pulled down, so leave as output-high.
+    gpio unexport "${gpio_pwren}"
+  fi
 
   # Put back cros_fp driver if transport is SPI
   if [[ "${transport}" != "UART" ]]; then
+    # wait for FP MCU to come back up (including RWSIG delay)
+    sleep 2
     klog "Binding cros-ec driver"
     echo "" > "/sys/bus/spi/devices/${deviceid}/driver_override"
     echo "${deviceid}" > /sys/bus/spi/drivers/cros-ec-spi/bind
@@ -434,8 +449,9 @@ flash_fp_mcu_stm32() {
     echo "Please reboot this device."
   else
     # Test it
-    klog "Query version"
+    klog "Query version and reset flags"
     ectool --name=cros_fp version
+    ectool --name=cros_fp uptimeinfo
   fi
 }