amlogic-aml8726-mx-kernel/drivers/amlogic/sensors/mpu3050

Kernel driver mpu
=====================

Supported chips:
* InvenSense IMU3050
Prefix: 'mpu3050'
Datasheet:
PS-MPU-3000A-00.2.4b.pdf

* InvenSense IMU6000
Prefix: 'mpu6000'
Datasheet:
MPU-6000A-00 v1.0.pdf

Author: InvenSense

Description
-----------
The mpu is a motion processor unit that controls the mpu3050 gyroscope, a slave
accelerometer, a compass and a pressure sensor, or the mpu6000 and slave
compass. This document describes how to install the driver into a Linux kernel
and a small note about how to set up the file permissions in an android file
system.

Sysfs entries
-------------
/dev/mpu
/dev/mpuirq
/dev/accelirq
/dev/compassirq
/dev/pressureirq

General Remarks MPU3050
-----------------------
* Valid addresses for the MPU3050 is 0x68.
* Accelerometer must be on the secondary I2C bus for MPU3050, the
magnetometer must be on the primary bus and pressure sensor must
be on the primary bus.

General Remarks MPU6000
-----------------------
* Valid addresses for the MPU6000 is 0x68.
* Magnetometer must be on the secondary I2C bus for the MPU6000.
* Accelerometer slave address must be set to 0x68
* Gyro and Accel orientation matrices should be the same

Programming the chip using /dev/mpu
----------------------------------
Programming of MPU3050 or MPU6000 is done by first opening the /dev/mpu file and
then performing a series of IOCTLS on the handle returned. The IOCTL codes can
be found in mpu.h. Typically this is done by the mllite library in user
space.

Adding to a Kernel
==================

The mpu driver is designed to be inserted in the drivers/misc part of the
kernel. Extracting the tarball from the root kernel dir will place the
contents of the tarball here:

/drivers/misc/mpu3050
/include/linux/mpu.h
/include/linux/mpu3050.h
/include/linux/mpu6000.h

After this is done the drivers/misc/Kconfig must be edited to add the line:

source "drivers/misc/mpu3050/Kconfig"

Similarly drivers/misc/Makefile must be edited to add the line:

obj-y += mpu3050/

Configuration can then be done as normal.

NOTE: This driver depends on a kernel patch to drivers/char/char.c. This patch
started to be included in most 2.6.35 based kernels.
drivers: misc: pass miscdevice pointer via file private data
https://patchwork.kernel.org/patch/96412/

---
drivers/char/misc.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)


diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 92ab03d..cd650ca 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -144,6 +144,7 @@ static int misc_open(struct inode * inode, struct file * file)
old_fops = file->f_op;
file->f_op = new_fops;
if (file->f_op->open) {
+ file->private_data = c;
err=file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
---

Board and Platform Data
-----------------------

In order for the driver to work, board and platform data specific to the device
needs to be added to the board file. A mpu3050_platform_data structure must
be created and populated and set in the i2c_board_info_structure. For details
of each structure member see mpu.h. All values below are simply an example and
should be modified for your platform.

#include

#if defined(CONFIG_MPU_SENSORS_MPU3050) || defined(CONFIG_MPU_SENSORS_MPU3050_MODULE)

#define SENSOR_MPU_NAME "mpu3050"

static struct mpu3050_platform_data mpu_data = {
.int_config = 0x10,
.orientation = { -1, 0, 0,
0, 1, 0,
0, 0, -1 },
/* accel */
.accel = {
#ifdef CONFIG_MPU_SENSORS_MPU3050_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_accel_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_SECONDARY,
.address = 0x0F,
.orientation = { -1, 0, 0,
0, 1, 0,
0, 0, -1 },
},
/* compass */
.compass = {
#ifdef CONFIG_MPU_SENSORS_MPU3050_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_compass_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_PRIMARY,
.address = 0x0E,
.orientation = { 1, 0, 0,
0, 1, 0,
0, 0, 1 },
},
/* pressure */
.pressure = {
#ifdef CONFIG_MPU_SENSORS_MPU3050_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_pressure_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_PRIMARY,
.address = 0x77,
.orientation = { 1, 0, 0,
0, 1, 0,
0, 0, 1 },
},
};
#endif

#if defined(CONFIG_MPU_SENSORS_MPU6000) || defined(CONFIG_MPU_SENSORS_MPU6000_MODULE)

#define SENSOR_MPU_NAME "mpu6000"

static struct mpu3050_platform_data mpu_data = {
.int_config = 0x10,
.orientation = { -1, 0, 0,
0, 1, 0,
0, 0, -1 },
/* accel */
.accel = {
#ifdef CONFIG_MPU_SENSORS_MPU6000_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_accel_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_PRIMARY,
.address = 0x68,
.orientation = { -1, 0, 0,
0, 1, 0,
0, 0, -1 },
},
/* compass */
.compass = {
#ifdef CONFIG_MPU_SENSORS_MPU6000_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_compass_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_SECONDARY,
.address = 0x0E,
.orientation = { 1, 0, 0,
0, 1, 0,
0, 0, 1 },
},
/* pressure */
.pressure = {
#ifdef CONFIG_MPU_SENSORS_MPU6000_MODULE
.get_slave_descr = NULL,
#else
.get_slave_descr = get_pressure_slave_descr,
#endif
.adapt_num = 2,
.bus = EXT_SLAVE_BUS_PRIMARY,
.address = 0x77,
.orientation = { 1, 0, 0,
0, 1, 0,
0, 0, 1 },
},

};
#endif

static struct i2c_board_info __initdata beagle_i2c_2_boardinfo[] = {
{
I2C_BOARD_INFO(SENSOR_MPU_NAME, 0x68),
.irq = (IH_GPIO_BASE + MPU_GPIO_IRQ),
.platform_data = &mpu_data,
},
};

Typically the IRQ is a GPIO input pin and needs to be configured properly. If
in the above example GPIO 168 corresponds to IRQ 299, the following should be
done as well:

#define MPU_GPIO_IRQ 168

gpio_request(MPU_GPIO_IRQ,"MPUIRQ");
gpio_direction_input(MPU_GPIO_IRQ)

NOTE:
=====
In previous releases, the sensors were defined using CONFIG_SENSORS_SENSORNAME convention.
From this release onwards this convention will be changed to CONFIG_MPU_SENSORS_SENSORNAME.
Please make note of this change.

Dynamic Debug
=============

The mpu3050 makes use of dynamic debug. For details on how to use this
refer to Documentation/dynamic-debug-howto.txt

Android File Permissions
========================

To set up the file permissions on an android system, the /dev/mpu and
/dev/mpuirq files needs to be added to the system/core/init/devices.c file
inside the perms_ structure.

static struct perms_ devperms[] = {
{ "/dev/mpu" ,0660, AID_SYSTEM, AID_SYSTEM, 1 },
};

Sufficient file permissions need to be give to read and write it by the system.

For gingerbread and later the system/core/rootdir/ueventd.rc file needs to be
modified with the appripriate lines added.

# MPU sensors and IRQ
/dev/mpu 0660 system system
/dev/mpuirq 0660 system system
/dev/accelirq 0660 system system
/dev/compassirq 0660 system system
/dev/pressureirq 0660 system system