Implement SPI driver for the Bosch BMI270 6-axis IMU. Provide raw read
write access to acceleration and angle velocity measurements via the SPI
interface on the device.

Signed-off-by: Alex Lanzano <lanzano.alex@gmail.com>
---
 drivers/iio/imu/bmi270/Kconfig       | 12 ++++
 drivers/iio/imu/bmi270/Makefile      |  1 +
 drivers/iio/imu/bmi270/bmi270.h      |  2 +
 drivers/iio/imu/bmi270/bmi270_core.c | 13 ++--
 drivers/iio/imu/bmi270/bmi270_i2c.c  |  7 ++-
 drivers/iio/imu/bmi270/bmi270_spi.c  | 89 ++++++++++++++++++++++++++++
 6 files changed, 114 insertions(+), 10 deletions(-)
 create mode 100644 drivers/iio/imu/bmi270/bmi270_spi.c

diff --git a/drivers/iio/imu/bmi270/Kconfig b/drivers/iio/imu/bmi270/Kconfig
index a8db44187286..0ffd29794fda 100644
--- a/drivers/iio/imu/bmi270/Kconfig
+++ b/drivers/iio/imu/bmi270/Kconfig
@@ -18,3 +18,15 @@ config BMI270_I2C
 
 	  This driver can also be built as a module. If so, the module will be
 	  called bmi270_i2c.
+
+config BMI270_SPI
+	tristate "Bosch BMI270 SPI driver"
+	depends on SPI
+	select BMI270
+	select REGMAP_SPI
+	help
+	  Enable support for the Bosch BMI270 6-Axis IMU connected to SPI
+	  interface.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called bmi270_spi.
diff --git a/drivers/iio/imu/bmi270/Makefile b/drivers/iio/imu/bmi270/Makefile
index ab4acaaee6d2..d96c96fc3d83 100644
--- a/drivers/iio/imu/bmi270/Makefile
+++ b/drivers/iio/imu/bmi270/Makefile
@@ -4,3 +4,4 @@
 #
 obj-$(CONFIG_BMI270) += bmi270_core.o
 obj-$(CONFIG_BMI270_I2C) += bmi270_i2c.o
+obj-$(CONFIG_BMI270_SPI) += bmi270_spi.o
diff --git a/drivers/iio/imu/bmi270/bmi270.h b/drivers/iio/imu/bmi270/bmi270.h
index 608b29ea58a3..8950e6234203 100644
--- a/drivers/iio/imu/bmi270/bmi270.h
+++ b/drivers/iio/imu/bmi270/bmi270.h
@@ -4,11 +4,13 @@
 #define BMI270_H_
 
 #include <linux/regmap.h>
+#include <linux/iio/iio.h>
 
 struct device;
 struct bmi270_data {
 	struct device *dev;
 	struct regmap *regmap;
+	__le16 sample __aligned(IIO_DMA_MINALIGN);
 };
 
 extern const struct regmap_config bmi270_regmap_config;
diff --git a/drivers/iio/imu/bmi270/bmi270_core.c b/drivers/iio/imu/bmi270/bmi270_core.c
index 8e45343d6472..4decdad791d9 100644
--- a/drivers/iio/imu/bmi270/bmi270_core.c
+++ b/drivers/iio/imu/bmi270/bmi270_core.c
@@ -66,16 +66,9 @@ enum bmi270_scan {
 	BMI270_SCAN_GYRO_Z,
 };
 
-const struct regmap_config bmi270_regmap_config = {
-	.reg_bits = 8,
-	.val_bits = 8,
-};
-EXPORT_SYMBOL_NS_GPL(bmi270_regmap_config, IIO_BMI270);
-
 static int bmi270_get_data(struct bmi270_data *bmi270_device,
 			   int chan_type, int axis, int *val)
 {
-	__le16 sample;
 	int reg;
 	int ret;
 
@@ -90,11 +83,13 @@ static int bmi270_get_data(struct bmi270_data *bmi270_device,
 		return -EINVAL;
 	}
 
-	ret = regmap_bulk_read(bmi270_device->regmap, reg, &sample, sizeof(sample));
+	ret = regmap_bulk_read(bmi270_device->regmap, reg,
+			       &bmi270_device->sample,
+			       sizeof(bmi270_device->sample));
 	if (ret)
 		return ret;
 
-	*val = sign_extend32(le16_to_cpu(sample), 15);
+	*val = sign_extend32(le16_to_cpu(bmi270_device->sample), 15);
 
 	return 0;
 }
diff --git a/drivers/iio/imu/bmi270/bmi270_i2c.c b/drivers/iio/imu/bmi270/bmi270_i2c.c
index f70dee2d8a64..ce8279ae90cd 100644
--- a/drivers/iio/imu/bmi270/bmi270_i2c.c
+++ b/drivers/iio/imu/bmi270/bmi270_i2c.c
@@ -9,12 +9,17 @@
 
 #include "bmi270.h"
 
+const struct regmap_config bmi270_i2c_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
 static int bmi270_i2c_probe(struct i2c_client *client)
 {
 	struct regmap *regmap;
 	struct device *dev = &client->dev;
 
-	regmap = devm_regmap_init_i2c(client, &bmi270_regmap_config);
+	regmap = devm_regmap_init_i2c(client, &bmi270_i2c_regmap_config);
 	if (IS_ERR(regmap))
 		return dev_err_probe(dev, PTR_ERR(regmap),
 				     "Failed to init i2c regmap");
diff --git a/drivers/iio/imu/bmi270/bmi270_spi.c b/drivers/iio/imu/bmi270/bmi270_spi.c
new file mode 100644
index 000000000000..906b9b852a09
--- /dev/null
+++ b/drivers/iio/imu/bmi270/bmi270_spi.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/regmap.h>
+
+#include "bmi270.h"
+
+/*
+ * The following two functions are taken from the BMI323 spi driver code.
+ * In section 6.4 of the BMI270 data it specifies that after a read
+ * operation the first data byte from the device is a dummy byte
+ */
+static int bmi270_regmap_spi_read(void *context, const void *reg_buf,
+				  size_t reg_size, void *val_buf,
+				  size_t val_size)
+{
+	struct spi_device *spi = context;
+
+	return spi_write_then_read(spi, reg_buf, reg_size, val_buf, val_size);
+}
+
+static int bmi270_regmap_spi_write(void *context, const void *data,
+				   size_t count)
+{
+	struct spi_device *spi = context;
+	u8 *data_buff = (u8 *)data;
+
+	/*
+	 * Remove the extra pad byte since its only needed for the read
+	 * operation
+	 */
+	data_buff[1] = data_buff[0];
+	return spi_write(spi, data_buff + 1, count - 1);
+}
+
+static const struct regmap_bus bmi270_regmap_bus = {
+	.read = bmi270_regmap_spi_read,
+	.write = bmi270_regmap_spi_write,
+};
+
+const struct regmap_config bmi270_spi_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.pad_bits = 8,
+	.read_flag_mask = BIT(7),
+};
+
+static int bmi270_spi_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+	struct device *dev = &spi->dev;
+
+	regmap = devm_regmap_init(dev, &bmi270_regmap_bus, dev,
+				  &bmi270_spi_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to init i2c regmap");
+
+	return bmi270_core_probe(dev, regmap);
+}
+
+static const struct spi_device_id bmi270_spi_id[] = {
+	{ "bmi270" },
+	{ }
+};
+
+static const struct of_device_id bmi270_of_match[] = {
+	{ .compatible = "bosch,bmi270" },
+	{ }
+};
+
+static struct spi_driver bmi270_spi_driver = {
+	.driver = {
+		.name = "bmi270",
+		.of_match_table = bmi270_of_match,
+	},
+	.probe = bmi270_spi_probe,
+	.id_table = bmi270_spi_id,
+};
+module_spi_driver(bmi270_spi_driver);
+
+MODULE_AUTHOR("Alex Lanzano");
+MODULE_DESCRIPTION("BMI270 driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(IIO_BMI270);
-- 
2.46.2

On Fri, 27 Sep 2024 14:37:10 -0400
Alex Lanzano <lanzano.alex@gmail.com> wrote:

> Implement SPI driver for the Bosch BMI270 6-axis IMU. Provide raw read
> write access to acceleration and angle velocity measurements via the SPI
> interface on the device.
> 
> Signed-off-by: Alex Lanzano <lanzano.alex@gmail.com>

A few minor things inline but looks good in general.

Jonathan

> diff --git a/drivers/iio/imu/bmi270/bmi270.h b/drivers/iio/imu/bmi270/bmi270.h
> index 608b29ea58a3..8950e6234203 100644
> --- a/drivers/iio/imu/bmi270/bmi270.h
> +++ b/drivers/iio/imu/bmi270/bmi270.h
> @@ -4,11 +4,13 @@
>  #define BMI270_H_
>  
>  #include <linux/regmap.h>
> +#include <linux/iio/iio.h>
>  
>  struct device;
>  struct bmi270_data {
>  	struct device *dev;
>  	struct regmap *regmap;
> +	__le16 sample __aligned(IIO_DMA_MINALIGN);

For the read path you are bouncing anyway, so the DMA_MINALIGN is only needed
for anything the write direction.  Make the suggested change below and that
will bounce as well so that you don't need this.

>  };
>  
>  extern const struct regmap_config bmi270_regmap_config;
> diff --git a/drivers/iio/imu/bmi270/bmi270_core.c b/drivers/iio/imu/bmi270/bmi270_core.c
> index 8e45343d6472..4decdad791d9 100644
> --- a/drivers/iio/imu/bmi270/bmi270_core.c
> +++ b/drivers/iio/imu/bmi270/bmi270_core.c
> @@ -66,16 +66,9 @@ enum bmi270_scan {
>  	BMI270_SCAN_GYRO_Z,
>  };
>  
> -const struct regmap_config bmi270_regmap_config = {
> -	.reg_bits = 8,
> -	.val_bits = 8,
> -};
> -EXPORT_SYMBOL_NS_GPL(bmi270_regmap_config, IIO_BMI270);
> -
>  static int bmi270_get_data(struct bmi270_data *bmi270_device,
>  			   int chan_type, int axis, int *val)
>  {
> -	__le16 sample;
>  	int reg;
>  	int ret;
>  
> @@ -90,11 +83,13 @@ static int bmi270_get_data(struct bmi270_data *bmi270_device,
>  		return -EINVAL;
>  	}
>  
> -	ret = regmap_bulk_read(bmi270_device->regmap, reg, &sample, sizeof(sample));
> +	ret = regmap_bulk_read(bmi270_device->regmap, reg,
> +			       &bmi270_device->sample,
> +			       sizeof(bmi270_device->sample));
>  	if (ret)
>  		return ret;
>  
> -	*val = sign_extend32(le16_to_cpu(sample), 15);
> +	*val = sign_extend32(le16_to_cpu(bmi270_device->sample), 15);
>  
>  	return 0;
>  }
> diff --git a/drivers/iio/imu/bmi270/bmi270_i2c.c b/drivers/iio/imu/bmi270/bmi270_i2c.c
> index f70dee2d8a64..ce8279ae90cd 100644
> --- a/drivers/iio/imu/bmi270/bmi270_i2c.c
> +++ b/drivers/iio/imu/bmi270/bmi270_i2c.c
> @@ -9,12 +9,17 @@
>  
>  #include "bmi270.h"
>  
> +const struct regmap_config bmi270_i2c_regmap_config = {
static const

(same for spi one)

> +	.reg_bits = 8,
> +	.val_bits = 8,
> +};
> +
>  static int bmi270_i2c_probe(struct i2c_client *client)
>  {
>  	struct regmap *regmap;
>  	struct device *dev = &client->dev;
>  
> -	regmap = devm_regmap_init_i2c(client, &bmi270_regmap_config);
> +	regmap = devm_regmap_init_i2c(client, &bmi270_i2c_regmap_config);
>  	if (IS_ERR(regmap))
>  		return dev_err_probe(dev, PTR_ERR(regmap),
>  				     "Failed to init i2c regmap");
> diff --git a/drivers/iio/imu/bmi270/bmi270_spi.c b/drivers/iio/imu/bmi270/bmi270_spi.c
> new file mode 100644
> index 000000000000..906b9b852a09
> --- /dev/null
> +++ b/drivers/iio/imu/bmi270/bmi270_spi.c
> @@ -0,0 +1,89 @@
> +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/regmap.h>
Alphabetical order preferred.

> +
> +#include "bmi270.h"
> +
> +/*
> + * The following two functions are taken from the BMI323 spi driver code.
> + * In section 6.4 of the BMI270 data it specifies that after a read
> + * operation the first data byte from the device is a dummy byte
> + */
> +static int bmi270_regmap_spi_read(void *context, const void *reg_buf,
> +				  size_t reg_size, void *val_buf,
> +				  size_t val_size)
> +{
> +	struct spi_device *spi = context;

I'd be tempted to rename the input parameter context to spi and then
parse it directly to the spi_write_then_read()

> +
> +	return spi_write_then_read(spi, reg_buf, reg_size, val_buf, val_size);
> +}
> +
> +static int bmi270_regmap_spi_write(void *context, const void *data,
> +				   size_t count)
> +{
> +	struct spi_device *spi = context;
> +	u8 *data_buff = (u8 *)data;
> +
> +	/*
> +	 * Remove the extra pad byte since its only needed for the read
> +	 * operation
> +	 */
> +	data_buff[1] = data_buff[0];
> +	return spi_write(spi, data_buff + 1, count - 1);
That needs a DMA safe buffer (unlike write_then_read which always
bounces).  I'd avoid that complexity by using spi_write_then_read
here as well but set the read to 0 length and pass NULL for the buffer.
That function is intended to be used like this as it special cases 0
length for either write or read buffers.

> +}

Thanks for the review!

On Sun, Sep 29, 2024 at 03:54:37PM GMT, Jonathan Cameron wrote:
> On Fri, 27 Sep 2024 14:37:10 -0400
> Alex Lanzano <lanzano.alex@gmail.com> wrote:
> 
> > Implement SPI driver for the Bosch BMI270 6-axis IMU. Provide raw read
> > write access to acceleration and angle velocity measurements via the SPI
> > interface on the device.
> > 
> > Signed-off-by: Alex Lanzano <lanzano.alex@gmail.com>
> 
> A few minor things inline but looks good in general.
> 
> Jonathan
> 
> > diff --git a/drivers/iio/imu/bmi270/bmi270.h b/drivers/iio/imu/bmi270/bmi270.h
> > index 608b29ea58a3..8950e6234203 100644
> > --- a/drivers/iio/imu/bmi270/bmi270.h
> > +++ b/drivers/iio/imu/bmi270/bmi270.h
> > @@ -4,11 +4,13 @@
> >  #define BMI270_H_
> >  
> >  #include <linux/regmap.h>
> > +#include <linux/iio/iio.h>
> >  
> >  struct device;
> >  struct bmi270_data {
> >  	struct device *dev;
> >  	struct regmap *regmap;
> > +	__le16 sample __aligned(IIO_DMA_MINALIGN);
> 
> For the read path you are bouncing anyway, so the DMA_MINALIGN is only needed
> for anything the write direction.  Make the suggested change below and that
> will bounce as well so that you don't need this.
> 

Understood! Will remove in v2 and use spi_write_then_read

> >  };
> >  
> >  extern const struct regmap_config bmi270_regmap_config;
> > diff --git a/drivers/iio/imu/bmi270/bmi270_core.c b/drivers/iio/imu/bmi270/bmi270_core.c
> > index 8e45343d6472..4decdad791d9 100644
> > --- a/drivers/iio/imu/bmi270/bmi270_core.c
> > +++ b/drivers/iio/imu/bmi270/bmi270_core.c
> > @@ -66,16 +66,9 @@ enum bmi270_scan {
> >  	BMI270_SCAN_GYRO_Z,
> >  };
> >  
> > -const struct regmap_config bmi270_regmap_config = {
> > -	.reg_bits = 8,
> > -	.val_bits = 8,
> > -};
> > -EXPORT_SYMBOL_NS_GPL(bmi270_regmap_config, IIO_BMI270);
> > -
> >  static int bmi270_get_data(struct bmi270_data *bmi270_device,
> >  			   int chan_type, int axis, int *val)
> >  {
> > -	__le16 sample;
> >  	int reg;
> >  	int ret;
> >  
> > @@ -90,11 +83,13 @@ static int bmi270_get_data(struct bmi270_data *bmi270_device,
> >  		return -EINVAL;
> >  	}
> >  
> > -	ret = regmap_bulk_read(bmi270_device->regmap, reg, &sample, sizeof(sample));
> > +	ret = regmap_bulk_read(bmi270_device->regmap, reg,
> > +			       &bmi270_device->sample,
> > +			       sizeof(bmi270_device->sample));
> >  	if (ret)
> >  		return ret;
> >  
> > -	*val = sign_extend32(le16_to_cpu(sample), 15);
> > +	*val = sign_extend32(le16_to_cpu(bmi270_device->sample), 15);
> >  
> >  	return 0;
> >  }
> > diff --git a/drivers/iio/imu/bmi270/bmi270_i2c.c b/drivers/iio/imu/bmi270/bmi270_i2c.c
> > index f70dee2d8a64..ce8279ae90cd 100644
> > --- a/drivers/iio/imu/bmi270/bmi270_i2c.c
> > +++ b/drivers/iio/imu/bmi270/bmi270_i2c.c
> > @@ -9,12 +9,17 @@
> >  
> >  #include "bmi270.h"
> >  
> > +const struct regmap_config bmi270_i2c_regmap_config = {
> static const
> 
> (same for spi one)
> 

Will fix in v2!

> > +	.reg_bits = 8,
> > +	.val_bits = 8,
> > +};
> > +
> >  static int bmi270_i2c_probe(struct i2c_client *client)
> >  {
> >  	struct regmap *regmap;
> >  	struct device *dev = &client->dev;
> >  
> > -	regmap = devm_regmap_init_i2c(client, &bmi270_regmap_config);
> > +	regmap = devm_regmap_init_i2c(client, &bmi270_i2c_regmap_config);
> >  	if (IS_ERR(regmap))
> >  		return dev_err_probe(dev, PTR_ERR(regmap),
> >  				     "Failed to init i2c regmap");
> > diff --git a/drivers/iio/imu/bmi270/bmi270_spi.c b/drivers/iio/imu/bmi270/bmi270_spi.c
> > new file mode 100644
> > index 000000000000..906b9b852a09
> > --- /dev/null
> > +++ b/drivers/iio/imu/bmi270/bmi270_spi.c
> > @@ -0,0 +1,89 @@
> > +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +
> > +#include <linux/module.h>
> > +#include <linux/spi/spi.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/module.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/regmap.h>
> Alphabetical order preferred.
> 

Will fix in v2

> > +
> > +#include "bmi270.h"
> > +
> > +/*
> > + * The following two functions are taken from the BMI323 spi driver code.
> > + * In section 6.4 of the BMI270 data it specifies that after a read
> > + * operation the first data byte from the device is a dummy byte
> > + */
> > +static int bmi270_regmap_spi_read(void *context, const void *reg_buf,
> > +				  size_t reg_size, void *val_buf,
> > +				  size_t val_size)
> > +{
> > +	struct spi_device *spi = context;
> 
> I'd be tempted to rename the input parameter context to spi and then
> parse it directly to the spi_write_then_read()
> 

Will do! I named it context since that's what the function pointer uses

> > +
> > +	return spi_write_then_read(spi, reg_buf, reg_size, val_buf, val_size);
> > +}
> > +
> > +static int bmi270_regmap_spi_write(void *context, const void *data,
> > +				   size_t count)
> > +{
> > +	struct spi_device *spi = context;
> > +	u8 *data_buff = (u8 *)data;
> > +
> > +	/*
> > +	 * Remove the extra pad byte since its only needed for the read
> > +	 * operation
> > +	 */
> > +	data_buff[1] = data_buff[0];
> > +	return spi_write(spi, data_buff + 1, count - 1);
> That needs a DMA safe buffer (unlike write_then_read which always
> bounces).  I'd avoid that complexity by using spi_write_then_read
> here as well but set the read to 0 length and pass NULL for the buffer.
> That function is intended to be used like this as it special cases 0
> length for either write or read buffers.
> 

Understood! Will fix in v2.

> > +}
>