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, 0 deletions

diff --git a/include/accelgyro.h b/include/accelgyro.h
index cc731cf794..2d415621d1 100644
--- a/include/accelgyro.h
+++ b/include/accelgyro.h
@@ -10,6 +10,14 @@
 
 /* Header file for accelerometer / gyro drivers. */
 
+/*
+ * EC reports sensor data on 16 bits. For accel/gyro/mag.. the MSB is the sign.
+ * For instance, for gravity,
+ * real_value[in g] = measured_value * range >> 15
+ */
+#define MOTION_SCALING_FACTOR (1 << 15)
+#define MOTION_ONE_G (9.80665f)
+
 struct accelgyro_drv {
 	/**
 	 * Initialize accelerometers.