motion_lid: Rewrite lid angle calculation based on chromium code

Use code from ash/wm/tablet_mode/tablet_mode_controller.cc, in
particular TabletModeController::HandleHingeRotation()
to calculate lid angle.
Add unit tests based on
ash/wm/tablet_mode/tablet_mode_controller_unittest.cc and the data file
accelerometer_test_data_literals.cc.

BUG=b:120346412
BRANCH=none
TEST=Check unit tests pass, check it compile on FPU based EC, EC without
FPU and no 64 bit support (ampton).
Check lid calculation is correct on eve:
- with "while true ; do ectool motionsense lid_angle ; sleep 1 ; done"
Check when hinge is almost vertical lid angle is close to constant or
marked are unrieliable.
Check when shaking device, lid angle is also unreliable
Check with evtest SW_TABLET_MODE event is trigger when lid angle is
available and cross 180 region.

Change-Id: I545f7333ed9b53accedb75f238f747f66bae1f5d
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1388844
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 8 insertions, 20 deletions

diff --git a/include/motion_lid.h b/include/motion_lid.h
index 110d614811..2816a70bdb 100644
--- a/include/motion_lid.h
+++ b/include/motion_lid.h
@@ -11,27 +11,15 @@
 #include "host_command.h"
 #include "math_util.h"
 
-/**
- * This structure defines all of the data needed to specify the orientation
- * of the base and lid accelerometers in order to calculate the lid angle.
+/*
+ * We will change our tablet mode status when we are "convinced" that it has
+ * changed.  This means we will have to consecutively calculate our new tablet
+ * mode while the angle is stable and come to the same conclusion.  The number
+ * of consecutive calculations is the debounce count with an interval between
+ * readings set by the motion_sense task.  This should avoid spurious forces
+ * that may trigger false transitions of the tablet mode switch.
  */
-struct accel_orientation {
-	/* Rotation matrix to rotate positive 90 degrees around the hinge. */
-	mat33_fp_t rot_hinge_90;
-
-	/*
-	 * Rotation matrix to rotate 180 degrees around the hinge. The value
-	 * here should be rot_hinge_90 ^ 2.
-	 */
-	mat33_fp_t rot_hinge_180;
-
-	/* Vector pointing along hinge axis. */
-	intv3_t hinge_axis;
-};
-
-/* Link global structure for orientation. This must be defined in board.c. */
-extern const struct accel_orientation acc_orient;
-
+#define TABLET_MODE_DEBOUNCE_COUNT 3
 
 /**
  * Get last calculated lid angle. Note, the lid angle calculated by the EC