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Date:   Sun, 7 Apr 2019 12:45:01 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     stevemo@skydio.com
Cc:     jmaneyrol@invensense.com, Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Martin Kelly <mkelly@xevo.com>,
        Jonathan Marek <jonathan@marek.ca>,
        Brian Masney <masneyb@onstation.org>,
        Randolph =?UTF-8?B?TWFhw59lbg==?= <gaireg@gaireg.de>,
        Douglas Fischer <fischerdouglasc@gmail.com>,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] iio: imu: mpu6050: Fix FIFO layout for ICM20602
Message-ID: <20190407124501.1a8b21d8@archlinux>
In-Reply-To: <20190403062910.5047-1-stevemo@skydio.com>
References: <20190326090238.23651-1-stevemo@skydio.com>
        <20190403062910.5047-1-stevemo@skydio.com>
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On Tue,  2 Apr 2019 23:28:56 -0700
stevemo@skydio.com wrote:

> 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 FIFO 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 specifically
> 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>
I'd like a reviewed-by or acked-by from Jean-Baptiste on this before
I take it.

thanks,

Jonathan

> ---
> v2: Read temperature when running in accel-only mode, too.
> 
>  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 |  3 ++
>  3 files changed, 64 insertions(+), 5 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..2ed4b98e0cd7 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 FIFO samples include temperature readings */
> +#define INV_ICM20602_BYTES_PER_TEMP_SENSOR   2
> +
>  /* 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 temperature */
> +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..57bd11bde56b 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> @@ -207,6 +207,9 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
>  	if (st->chip_config.gyro_fifo_enable)
>  		bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
>  
> +	if (st->chip_type == INV_ICM20602)
> +		bytes_per_datum += INV_ICM20602_BYTES_PER_TEMP_SENSOR;
> +
>  	/*
>  	 * read fifo_count register to know how many bytes are inside the FIFO
>  	 * right now