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Date: Sat, 16 Apr 2022 17:38:33 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Jagath Jog J <jagathjog1996@...il.com>
Cc: dan@...obertson.com, andy.shevchenko@...il.com,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/9] iio: accel: bma400: Add triggered buffer support
On Tue, 12 Apr 2022 02:01:28 +0530
Jagath Jog J <jagathjog1996@...il.com> wrote:
> Added trigger buffer support to read continuous acceleration
> data from device with data ready interrupt which is mapped
> to INT1 pin.
>
> Signed-off-by: Jagath Jog J <jagathjog1996@...il.com>
A few comments inline.
Jonathan
> ---
> drivers/iio/accel/Kconfig | 2 +
> drivers/iio/accel/bma400.h | 10 ++-
> drivers/iio/accel/bma400_core.c | 153 ++++++++++++++++++++++++++++++--
> drivers/iio/accel/bma400_i2c.c | 2 +-
> drivers/iio/accel/bma400_spi.c | 2 +-
> 5 files changed, 161 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index eac3f02662ae..958097814232 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -204,6 +204,8 @@ config BMA220
> config BMA400
> tristate "Bosch BMA400 3-Axis Accelerometer Driver"
> select REGMAP
> + select IIO_BUFFER
> + select IIO_TRIGGERED_BUFFER
> select BMA400_I2C if I2C
> select BMA400_SPI if SPI
> help
> diff --git a/drivers/iio/accel/bma400.h b/drivers/iio/accel/bma400.h
> index 8dbf85eeb005..a7482a66b36b 100644
> --- a/drivers/iio/accel/bma400.h
> +++ b/drivers/iio/accel/bma400.h
> @@ -62,6 +62,13 @@
> #define BMA400_ACC_CONFIG2_REG 0x1b
> #define BMA400_CMD_REG 0x7e
>
> +/* Interrupt registers */
> +#define BMA400_INT_CONFIG0_REG 0x1f
> +#define BMA400_INT_CONFIG1_REG 0x20
> +#define BMA400_INT1_MAP_REG 0x21
> +#define BMA400_INT_IO_CTRL_REG 0x24
> +#define BMA400_INT_DRDY_MSK BIT(7)
> +
> /* Chip ID of BMA 400 devices found in the chip ID register. */
> #define BMA400_ID_REG_VAL 0x90
>
> @@ -111,6 +118,7 @@
>
> extern const struct regmap_config bma400_regmap_config;
>
> -int bma400_probe(struct device *dev, struct regmap *regmap, const char *name);
> +int bma400_probe(struct device *dev, struct regmap *regmap, int irq,
> + const char *name);
>
> #endif
> diff --git a/drivers/iio/accel/bma400_core.c b/drivers/iio/accel/bma400_core.c
> index 07674d89d978..b7b2b67aef31 100644
> --- a/drivers/iio/accel/bma400_core.c
> +++ b/drivers/iio/accel/bma400_core.c
> @@ -11,6 +11,7 @@
> * - Create channel for sensor time
> */
>
> +#include <linux/bitfield.h>
> #include <linux/bitops.h>
> #include <linux/device.h>
> #include <linux/kernel.h>
> @@ -20,6 +21,10 @@
> #include <linux/regulator/consumer.h>
>
> #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
>
> #include "bma400.h"
>
> @@ -61,6 +66,13 @@ struct bma400_data {
> struct bma400_sample_freq sample_freq;
> int oversampling_ratio;
> int scale;
> + struct iio_trigger *trig;
> + /* Correct time stamp alignment */
> + struct {
> + __le16 buff[3];
> + u8 temperature;
> + s64 ts __aligned(8);
> + } buffer ____cacheline_aligned;
See below, but I'd suggest adding
__le16 status;
here to be in the same cacheline as the buffer and hence also DMA safe (as it's
not in the same line as anything else which could be modified concurrently.)
> };
>
> static bool bma400_is_writable_reg(struct device *dev, unsigned int reg)
> @@ -152,7 +164,7 @@ static const struct iio_chan_spec_ext_info bma400_ext_info[] = {
> { }
> };
>
> -#define BMA400_ACC_CHANNEL(_axis) { \
> +#define BMA400_ACC_CHANNEL(_index, _axis) { \
> .type = IIO_ACCEL, \
> .modified = 1, \
> .channel2 = IIO_MOD_##_axis, \
> @@ -164,17 +176,32 @@ static const struct iio_chan_spec_ext_info bma400_ext_info[] = {
> BIT(IIO_CHAN_INFO_SCALE) | \
> BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> .ext_info = bma400_ext_info, \
> + .scan_index = _index, \
> + .scan_type = { \
> + .sign = 's', \
> + .realbits = 12, \
> + .storagebits = 16, \
> + .endianness = IIO_LE, \
> + }, \
> }
>
> static const struct iio_chan_spec bma400_channels[] = {
> - BMA400_ACC_CHANNEL(X),
> - BMA400_ACC_CHANNEL(Y),
> - BMA400_ACC_CHANNEL(Z),
> + BMA400_ACC_CHANNEL(0, X),
> + BMA400_ACC_CHANNEL(1, Y),
> + BMA400_ACC_CHANNEL(2, Z),
> {
> .type = IIO_TEMP,
> .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> + .scan_index = 3,
> + .scan_type = {
> + .sign = 's',
> + .realbits = 8,
> + .storagebits = 8,
> + .endianness = IIO_LE,
> + },
> },
> + IIO_CHAN_SOFT_TIMESTAMP(4),
> };
>
> static int bma400_get_temp_reg(struct bma400_data *data, int *val, int *val2)
> @@ -659,6 +686,10 @@ static int bma400_init(struct bma400_data *data)
> if (ret)
> return ret;
>
> + /* Configure INT1 pin to open drain */
> + ret = regmap_write(data->regmap, BMA400_INT_IO_CTRL_REG, 0x06);
> + if (ret)
> + return ret;
> /*
> * Once the interrupt engine is supported we might use the
> * data_src_reg, but for now ensure this is set to the
> @@ -807,6 +838,29 @@ static int bma400_write_raw_get_fmt(struct iio_dev *indio_dev,
> }
> }
>
> +static int bma400_data_rdy_trigger_set_state(struct iio_trigger *trig,
> + bool state)
> +{
> + struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> + struct bma400_data *data = iio_priv(indio_dev);
> + int ret;
> +
> + ret = regmap_update_bits(data->regmap, BMA400_INT_CONFIG0_REG,
> + BMA400_INT_DRDY_MSK,
> + FIELD_PREP(BMA400_INT_DRDY_MSK, state));
> + if (ret)
> + return ret;
> +
> + return regmap_update_bits(data->regmap, BMA400_INT1_MAP_REG,
> + BMA400_INT_DRDY_MSK,
> + FIELD_PREP(BMA400_INT_DRDY_MSK, state));
> +}
> +
> +static const unsigned long bma400_avail_scan_masks[] = {
> + GENMASK(3, 0),
> + 0
> +};
> +
> static const struct iio_info bma400_info = {
> .read_raw = bma400_read_raw,
> .read_avail = bma400_read_avail,
> @@ -814,7 +868,64 @@ static const struct iio_info bma400_info = {
> .write_raw_get_fmt = bma400_write_raw_get_fmt,
> };
>
> -int bma400_probe(struct device *dev, struct regmap *regmap, const char *name)
> +static const struct iio_trigger_ops bma400_trigger_ops = {
> + .set_trigger_state = &bma400_data_rdy_trigger_set_state,
> + .validate_device = &iio_trigger_validate_own_device,
> +};
> +
> +static irqreturn_t bma400_trigger_handler(int irq, void *p)
> +{
> + struct iio_poll_func *pf = p;
> + struct iio_dev *indio_dev = pf->indio_dev;
> + struct bma400_data *data = iio_priv(indio_dev);
> + int ret, temp;
> +
> + mutex_lock(&data->mutex);
> +
> + /* bulk read six registers, with the base being the LSB register */
> + ret = regmap_bulk_read(data->regmap, BMA400_X_AXIS_LSB_REG,
> + &data->buffer.buff, sizeof(data->buffer.buff));
> + mutex_unlock(&data->mutex);
> + if (ret)
> + return IRQ_NONE;
> +
> + ret = regmap_read(data->regmap, BMA400_TEMP_DATA_REG, &temp);
> + if (ret)
> + return IRQ_NONE;
> +
> + data->buffer.temperature = temp;
> +
> + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> + iio_get_time_ns(indio_dev));
> +
> + iio_trigger_notify_done(indio_dev->trig);
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t bma400_interrupt(int irq, void *private)
> +{
> + struct iio_dev *indio_dev = private;
> + struct bma400_data *data = iio_priv(indio_dev);
> + int ret;
> + __le16 status;
> +
> + mutex_lock(&data->mutex);
> + ret = regmap_bulk_read(data->regmap, BMA400_INT_STAT0_REG, &status,
> + sizeof(status));
regmap_bulk_read() (may) need a DMA safe buffer. Which means you can't use
a variable on the stack. Look at using the carefully aligned and padded
data->buffer if you can as that is DMA safe.
Note that then you will need that lock as it protects that buffer...
You could also just add a suitable buffer after that instead
of reusing that particular structure.
> + mutex_unlock(&data->mutex);
> + if (ret)
> + return IRQ_NONE;
> +
> + if (FIELD_GET(BMA400_INT_DRDY_MSK, le16_to_cpu(status))) {
> + iio_trigger_poll_chained(data->trig);
> + return IRQ_HANDLED;
> + }
> +
> + return IRQ_NONE;
> +}
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