commit fc0c77097ba960aa1e2a6388770fea905ab0d4a7
author Tom Wai-Hong Tam <waihong@chromium.org> Sat Sep 12 03:43:53 2015 +0800
committer chrome-bot <chrome-bot@chromium.org> Tue Sep 15 11:02:43 2015 -0700
tree 2a22083a51690893bbff8be1eebbeb8c4a09b21c
parent dacb0c940bb77a897db8ec276be3dd8d3aaad2d4

FAFT: Simplify reading/modifying GBB flags

The original code reads the GBB flags multiple time. Reading GBB
flags is slow on embedded devices. This change reduces the number
of reads.

BUG=None
TEST=Ran a FAFT test to exercise the change.

Change-Id: Ib8ec6c9db8ef83fa5e60fb18073fafcaf10cf269
Reviewed-on: https://chromium-review.googlesource.com/299390
Commit-Ready: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@chromium.org>

server/cros/faft/firmware_test.py

diff --git a/server/cros/faft/firmware_test.py b/server/cros/faft/firmware_test.py
index 399a199..09fd165 100644
--- a/server/cros/faft/firmware_test.py
+++ b/server/cros/faft/firmware_test.py
@@ -441,21 +441,6 @@
         command = 'status %s | grep start || start %s' % (service, service)
         self.faft_client.system.run_shell_command(command)
 
-    def _write_gbb_flags(self, new_flags):
-        """Write the GBB flags to the current firmware.
-
-        @param new_flags: The flags to write.
-        """
-        gbb_flags = self.faft_client.bios.get_gbb_flags()
-        if gbb_flags == new_flags:
-            return
-        logging.info('Changing GBB flags from 0x%x to 0x%x.',
-                     gbb_flags, new_flags)
-        self.faft_client.bios.set_gbb_flags(new_flags)
-        # If changing FORCE_DEV_SWITCH_ON flag, reboot to get a clear state
-        if ((gbb_flags ^ new_flags) & vboot.GBB_FLAG_FORCE_DEV_SWITCH_ON):
-            self.switcher.mode_aware_reboot()
-
     def clear_set_gbb_flags(self, clear_mask, set_mask):
         """Clear and set the GBB flags in the current flashrom.
 
@@ -464,7 +449,17 @@
         """
         gbb_flags = self.faft_client.bios.get_gbb_flags()
         new_flags = gbb_flags & ctypes.c_uint32(~clear_mask).value | set_mask
-        self._write_gbb_flags(new_flags)
+        if new_flags != gbb_flags:
+            self._backup_gbb_flags = gbb_flags
+            logging.info('Changing GBB flags from 0x%x to 0x%x.',
+                         gbb_flags, new_flags)
+            self.faft_client.bios.set_gbb_flags(new_flags)
+            # If changing FORCE_DEV_SWITCH_ON flag, reboot to get a clear state
+            if ((gbb_flags ^ new_flags) & vboot.GBB_FLAG_FORCE_DEV_SWITCH_ON):
+                self.switcher.mode_aware_reboot()
+        else:
+            logging.info('Current GBB flags look good for test: 0x%x.',
+                         gbb_flags)
 
     def check_ec_capability(self, required_cap=None, suppress_warning=False):
         """Check if current platform has required EC capabilities.
@@ -731,8 +726,6 @@
         if self.check_setup_done('gbb_flags'):
             return
 
-        self._backup_gbb_flags = self.faft_client.bios.get_gbb_flags()
-
         logging.info('Set proper GBB flags for test.')
         self.clear_set_gbb_flags(vboot.GBB_FLAG_DEV_SCREEN_SHORT_DELAY |
                                  vboot.GBB_FLAG_FORCE_DEV_SWITCH_ON |
@@ -752,7 +745,7 @@
 
     def _restore_gbb_flags(self):
         """Restore GBB flags to their original state."""
-        if not self._backup_gbb_flags:
+        if self._backup_gbb_flags is None:
             return
         # Setting up and restoring the GBB flags take a lot of time. For
         # speed-up purpose, don't restore it.