[PATCH] iio: imu: mpu6050: Fix FIFO layout for ICM20602

[stevemo@skydio.com]

From: Steve Moskovchenko <stevemo@skydio.com>

The MPU6050 driver has recently gained support for the
ICM20602 IMU, which is very similar to MPU6xxx. However,
the ICM20602's Gyro data specifically includes temperature
readings, which were not present on MPU6xxx parts. As a
result, the driver will under-read the ICM20602's FIFO
register, causing the same (partial) sample to be returned
for all reads, until the FIFO overflows.

Fix this by adding a table of scan elements speciically for
the ICM20602, which takes the extra temperature data into
consideration.

While we're at it, fix the temperature offset and scaling
on ICM20602, since it uses different scale/offset constants
than the rest of the MPU6xxx devices.

Signed-off-by: Steve Moskovchenko <stevemo@skydio.com>
---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 46 ++++++++++++++++++++--
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  | 20 +++++++++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c |  8 +++-
 3 files changed, 67 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
index 650de0fefb7b..fedd3f2b0135 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
@@ -471,7 +471,10 @@ inv_mpu6050_read_raw(struct iio_dev *indio_dev,
 			return IIO_VAL_INT_PLUS_MICRO;
 		case IIO_TEMP:
 			*val = 0;
-			*val2 = INV_MPU6050_TEMP_SCALE;
+			if (st->chip_type == INV_ICM20602)
+				*val2 = INV_ICM20602_TEMP_SCALE;
+			else
+				*val2 = INV_MPU6050_TEMP_SCALE;
 
 			return IIO_VAL_INT_PLUS_MICRO;
 		default:
@@ -480,7 +483,10 @@ inv_mpu6050_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_OFFSET:
 		switch (chan->type) {
 		case IIO_TEMP:
-			*val = INV_MPU6050_TEMP_OFFSET;
+			if (st->chip_type == INV_ICM20602)
+				*val = INV_ICM20602_TEMP_OFFSET;
+			else
+				*val = INV_MPU6050_TEMP_OFFSET;
 
 			return IIO_VAL_INT;
 		default:
@@ -845,6 +851,32 @@ static const struct iio_chan_spec inv_mpu_channels[] = {
 	INV_MPU6050_CHAN(IIO_ACCEL, IIO_MOD_Z, INV_MPU6050_SCAN_ACCL_Z),
 };
 
+static const struct iio_chan_spec inv_icm20602_channels[] = {
+	IIO_CHAN_SOFT_TIMESTAMP(INV_ICM20602_SCAN_TIMESTAMP),
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
+				| BIT(IIO_CHAN_INFO_OFFSET)
+				| BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = INV_ICM20602_SCAN_GYRO_TEMP,
+		.scan_type = {
+				.sign = 's',
+				.realbits = 16,
+				.storagebits = 16,
+				.shift = 0,
+				.endianness = IIO_BE,
+			     },
+	},
+
+	INV_MPU6050_CHAN(IIO_ANGL_VEL, IIO_MOD_X, INV_ICM20602_SCAN_GYRO_X),
+	INV_MPU6050_CHAN(IIO_ANGL_VEL, IIO_MOD_Y, INV_ICM20602_SCAN_GYRO_Y),
+	INV_MPU6050_CHAN(IIO_ANGL_VEL, IIO_MOD_Z, INV_ICM20602_SCAN_GYRO_Z),
+
+	INV_MPU6050_CHAN(IIO_ACCEL, IIO_MOD_Y, INV_ICM20602_SCAN_ACCL_Y),
+	INV_MPU6050_CHAN(IIO_ACCEL, IIO_MOD_X, INV_ICM20602_SCAN_ACCL_X),
+	INV_MPU6050_CHAN(IIO_ACCEL, IIO_MOD_Z, INV_ICM20602_SCAN_ACCL_Z),
+};
+
 /*
  * The user can choose any frequency between INV_MPU6050_MIN_FIFO_RATE and
  * INV_MPU6050_MAX_FIFO_RATE, but only these frequencies are matched by the
@@ -1100,8 +1132,14 @@ int inv_mpu_core_probe(struct regmap *regmap, int irq, const char *name,
 		indio_dev->name = name;
 	else
 		indio_dev->name = dev_name(dev);
-	indio_dev->channels = inv_mpu_channels;
-	indio_dev->num_channels = ARRAY_SIZE(inv_mpu_channels);
+
+	if (chip_type == INV_ICM20602) {
+		indio_dev->channels = inv_icm20602_channels;
+		indio_dev->num_channels = ARRAY_SIZE(inv_icm20602_channels);
+	} else {
+		indio_dev->channels = inv_mpu_channels;
+		indio_dev->num_channels = ARRAY_SIZE(inv_mpu_channels);
+	}
 
 	indio_dev->info = &mpu_info;
 	indio_dev->modes = INDIO_BUFFER_TRIGGERED;
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
index 325afd9f5f61..eb04391feaa8 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
@@ -208,6 +208,9 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_BYTES_PER_3AXIS_SENSOR   6
 #define INV_MPU6050_FIFO_COUNT_BYTE          2
 
+/* ICM20602 gyro data includes temperature */
+#define INV_ICM20602_BYTES_PER_GYRO_SENSOR   8
+
 /* mpu6500 registers */
 #define INV_MPU6500_REG_ACCEL_CONFIG_2      0x1D
 #define INV_MPU6500_REG_ACCEL_OFFSET        0x77
@@ -229,6 +232,9 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_GYRO_CONFIG_FSR_SHIFT    3
 #define INV_MPU6050_ACCL_CONFIG_FSR_SHIFT    3
 
+#define INV_ICM20602_TEMP_OFFSET	     8170
+#define INV_ICM20602_TEMP_SCALE		     3060
+
 /* 6 + 6 round up and plus 8 */
 #define INV_MPU6050_OUTPUT_DATA_SIZE         24
 
@@ -270,7 +276,7 @@ struct inv_mpu6050_state {
 #define INV_ICM20608_WHOAMI_VALUE		0xAF
 #define INV_ICM20602_WHOAMI_VALUE		0x12
 
-/* scan element definition */
+/* scan element definition for generic MPU6xxx devices */
 enum inv_mpu6050_scan {
 	INV_MPU6050_SCAN_ACCL_X,
 	INV_MPU6050_SCAN_ACCL_Y,
@@ -281,6 +287,18 @@ enum inv_mpu6050_scan {
 	INV_MPU6050_SCAN_TIMESTAMP,
 };
 
+/* scan element definition for ICM20602, which includes gyro temp */
+enum inv_icm20602_scan {
+	INV_ICM20602_SCAN_ACCL_X,
+	INV_ICM20602_SCAN_ACCL_Y,
+	INV_ICM20602_SCAN_ACCL_Z,
+	INV_ICM20602_SCAN_GYRO_TEMP,
+	INV_ICM20602_SCAN_GYRO_X,
+	INV_ICM20602_SCAN_GYRO_Y,
+	INV_ICM20602_SCAN_GYRO_Z,
+	INV_ICM20602_SCAN_TIMESTAMP,
+};
+
 enum inv_mpu6050_filter_e {
 	INV_MPU6050_FILTER_256HZ_NOLPF2 = 0,
 	INV_MPU6050_FILTER_188HZ,
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
index 548e042f7b5b..20828d6a13f9 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
@@ -204,8 +204,12 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	if (st->chip_config.accl_fifo_enable)
 		bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
 
-	if (st->chip_config.gyro_fifo_enable)
-		bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
+	if (st->chip_config.gyro_fifo_enable) {
+		if (st->chip_type == INV_ICM20602)
+			bytes_per_datum += INV_ICM20602_BYTES_PER_GYRO_SENSOR;
+		else
+			bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
+	}
 
 	/*
 	 * read fifo_count register to know how many bytes are inside the FIFO
-- 
2.20.1