Re: [PATCH 4/4] iio: accel: bmc150: Add support for BMC156

[Stephan Gerhold <stephan@gerhold.net>]

Hi Jonathan!

On Sat, Jul 24, 2021 at 05:12:46PM +0100, Jonathan Cameron wrote:
> On Mon, 19 Jul 2021 13:21:56 +0200
> Stephan Gerhold <stephan@gerhold.net> wrote:
> 
> > BMC156 is another accelerometer that works just fine with the bmc150-accel
> > driver. It's very similar to BMC150 (also a accelerometer+magnetometer
> > combo) but with only one accelerometer interrupt pin. It would make sense
> > if only INT1 was exposed but someone at Bosch was crazy and decided to only
> > have an INT2 pin.
> > 
> > Try to deal with this by making use of the INT2 support introduced
> > in the previous commit and force using INT2 for BMC156. To detect
> > that we need to bring up a simplified version of the previous type IDs.
> > 
> > Note that unlike the type IDs removed in commit c06a6aba6835
> > ("iio: accel: bmc150: Drop misleading/duplicate chip identifiers")
> > here I only add one for the special case of BMC156. Everything else
> > still happens by reading the CHIP_ID register since the chip type
> > information often is not accurate in ACPI tables.
> > 
> > Tested-by: Nikita Travkin <nikita@trvn.ru> # BMC156
> > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> A few really minor things inline.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/iio/accel/Kconfig             |  5 +++--
> >  drivers/iio/accel/bmc150-accel-core.c |  8 +++++---
> >  drivers/iio/accel/bmc150-accel-i2c.c  | 10 ++++++++--
> >  drivers/iio/accel/bmc150-accel-spi.c  | 10 +++++++++-
> >  drivers/iio/accel/bmc150-accel.h      |  9 ++++++++-
> >  5 files changed, 33 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> > index 0e56ace61103..2f0c0d512ae7 100644
> > --- a/drivers/iio/accel/Kconfig
> > +++ b/drivers/iio/accel/Kconfig
> > @@ -143,10 +143,11 @@ config BMC150_ACCEL
> >  	select BMC150_ACCEL_SPI if SPI
> >  	help
> >  	  Say yes here to build support for the following Bosch accelerometers:
> > -	  BMA222, BMA222E, BMA250E, BMA253, BMA254, BMA255, BMA280, BMC150, BMI055.
> > +	  BMA222, BMA222E, BMA250E, BMA253, BMA254, BMA255, BMA280, BMC150, BMC156
> > +	  BMI055.
> >  
> >  	  Note that some of these are combo modules:
> > -	    - BMC150: accelerometer and magnetometer
> > +	    - BMC150/BMC156: accelerometer and magnetometer
> >  	    - BMI055: accelerometer and gyroscope
> >  
> >  	  This driver is only implementing accelerometer part, which has
> > diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> > index 8d3dd3c2bcc2..a5d321e878ef 100644
> > --- a/drivers/iio/accel/bmc150-accel-core.c
> > +++ b/drivers/iio/accel/bmc150-accel-core.c
> > @@ -553,7 +553,7 @@ static void bmc150_accel_interrupts_setup(struct iio_dev *indio_dev,
> >  	 * Without interrupt-names, we assume the irq belongs to INT1.
> >  	 */
> >  	irq_info = bmc150_accel_interrupts_int1;
> > -	if (irq == of_irq_get_byname(dev->of_node, "INT2"))
> > +	if (data->type == BOSCH_BMC156 || irq == of_irq_get_byname(dev->of_node, "INT2"))
> 
> It is still preferred to keep line lengths under 80 chars unless it hurts
> readability to do so.  So please wrap this one.
> 

OK, will fix this in v2. :)

> >  		irq_info = bmc150_accel_interrupts_int2;
> >  
> >  	for (i = 0; i < BMC150_ACCEL_INTERRUPTS; i++)
> > @@ -1174,7 +1174,7 @@ static const struct bmc150_accel_chip_info bmc150_accel_chip_info_tbl[] = {
> >  				 {306458, BMC150_ACCEL_DEF_RANGE_16G} },
> >  	},
> >  	{
> > -		.name = "BMA253/BMA254/BMA255/BMC150/BMI055",
> > +		.name = "BMA253/BMA254/BMA255/BMC150/BMC156/BMI055",
> >  		.chip_id = 0xFA,
> >  		.channels = bmc150_accel_channels,
> >  		.num_channels = ARRAY_SIZE(bmc150_accel_channels),
> > @@ -1661,7 +1661,8 @@ static int bmc150_accel_chip_init(struct bmc150_accel_data *data)
> >  }
> >  
> >  int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
> > -			    const char *name, bool block_supported)
> > +			    enum bmc150_type type, const char *name,
> > +			    bool block_supported)
> >  {
> >  	const struct attribute **fifo_attrs;
> >  	struct bmc150_accel_data *data;
> > @@ -1676,6 +1677,7 @@ int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
> >  	dev_set_drvdata(dev, indio_dev);
> >  
> >  	data->regmap = regmap;
> > +	data->type = type;
> >  
> >  	if (!bmc150_apply_acpi_orientation(dev, &data->orientation)) {
> >  		ret = iio_read_mount_matrix(dev, &data->orientation);
> > diff --git a/drivers/iio/accel/bmc150-accel-i2c.c b/drivers/iio/accel/bmc150-accel-i2c.c
> > index 999495f0669d..88bd8a25f142 100644
> > --- a/drivers/iio/accel/bmc150-accel-i2c.c
> > +++ b/drivers/iio/accel/bmc150-accel-i2c.c
> > @@ -176,6 +176,7 @@ static int bmc150_accel_probe(struct i2c_client *client,
> >  {
> >  	struct regmap *regmap;
> >  	const char *name = NULL;
> > +	enum bmc150_type type = BOSCH_UNKNOWN;
> >  	bool block_supported =
> >  		i2c_check_functionality(client->adapter, I2C_FUNC_I2C) ||
> >  		i2c_check_functionality(client->adapter,
> > @@ -188,10 +189,13 @@ static int bmc150_accel_probe(struct i2c_client *client,
> >  		return PTR_ERR(regmap);
> >  	}
> >  
> > -	if (id)
> > +	if (id) {
> >  		name = id->name;
> > +		type = id->driver_data;
> > +	}
> >  
> > -	ret = bmc150_accel_core_probe(&client->dev, regmap, client->irq, name, block_supported);
> > +	ret = bmc150_accel_core_probe(&client->dev, regmap, client->irq,
> > +				      type, name, block_supported);
> >  	if (ret)
> >  		return ret;
> >  
> > @@ -236,6 +240,7 @@ static const struct i2c_device_id bmc150_accel_id[] = {
> >  	{"bma255"},
> >  	{"bma280"},
> >  	{"bmc150_accel"},
> > +	{"bmc156_accel", BOSCH_BMC156},
> >  	{"bmi055_accel"},
> >  	{}
> >  };
> > @@ -251,6 +256,7 @@ static const struct of_device_id bmc150_accel_of_match[] = {
> >  	{ .compatible = "bosch,bma255" },
> >  	{ .compatible = "bosch,bma280" },
> >  	{ .compatible = "bosch,bmc150_accel" },
> > +	{ .compatible = "bosch,bmc156_accel" },
> >  	{ .compatible = "bosch,bmi055_accel" },
> >  	{ },
> >  };
> > diff --git a/drivers/iio/accel/bmc150-accel-spi.c b/drivers/iio/accel/bmc150-accel-spi.c
> > index 54b8c9c8068b..191e312dc91a 100644
> > --- a/drivers/iio/accel/bmc150-accel-spi.c
> > +++ b/drivers/iio/accel/bmc150-accel-spi.c
> > @@ -16,6 +16,8 @@
> >  static int bmc150_accel_probe(struct spi_device *spi)
> >  {
> >  	struct regmap *regmap;
> > +	const char *name = NULL;
> > +	enum bmc150_type type = BOSCH_UNKNOWN;
> >  	const struct spi_device_id *id = spi_get_device_id(spi);
> >  
> >  	regmap = devm_regmap_init_spi(spi, &bmc150_regmap_conf);
> > @@ -24,7 +26,12 @@ static int bmc150_accel_probe(struct spi_device *spi)
> >  		return PTR_ERR(regmap);
> >  	}
> >  
> > -	return bmc150_accel_core_probe(&spi->dev, regmap, spi->irq, id->name,
> > +	if (id) {
> > +		name = id->name;
> > +		type = id->driver_data;
> > +	}
> > +
> > +	return bmc150_accel_core_probe(&spi->dev, regmap, spi->irq, type, name,
> >  				       true);
> >  }
> >  
> > @@ -54,6 +61,7 @@ static const struct spi_device_id bmc150_accel_id[] = {
> >  	{"bma255"},
> >  	{"bma280"},
> >  	{"bmc150_accel"},
> > +	{"bmc156_accel", BOSCH_BMC156},
> >  	{"bmi055_accel"},
> >  	{}
> >  };
> > diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
> > index 47121f070fe9..a3f4905e48a3 100644
> > --- a/drivers/iio/accel/bmc150-accel.h
> > +++ b/drivers/iio/accel/bmc150-accel.h
> > @@ -13,6 +13,11 @@ struct i2c_client;
> >  struct bmc150_accel_chip_info;
> >  struct bmc150_accel_interrupt_info;
> >  
> > +enum bmc150_type {
> > +	BOSCH_UNKNOWN,
> > +	BOSCH_BMC156,
> Whilst we only need to distinguish this one at the moment, the unknown naming
> implies we don't know the type when often we actually do.
> 

Hm, actually this is exactly what I want to imply! We do have seemingly
obvious names listed in the ID tables, but unfortunately I don't think
we can assume them to be accurate.

The original reason why we no longer rely on the type implied by the ID
is that there are some ACPI devices that specify an ID like "BMA250E"
when they actually have a BMA222E, see commit 0ad4bf37017 [1]
("iio:accel:bmc150-accel: Use the chip ID to detect sensor variant").

And this was the motivation for my commit c06a6aba6835 [2]
("iio: accel: bmc150: Drop misleading/duplicate chip identifiers").
I removed them because they were not used. Also, we cannot make use of
them in the general case because they are not reliable thanks to those
ACPI devices.

We could perhaps add it only for the of_device_ids. However, even there
it's easy to specify some similar compatible only because Bosch has so
many compatible parts. For example, the device where these BMC156
changes were tested on was using "bosch,bmc150_accel" so far simply
because this was working fine (without interrupts) and we weren't
actually aware that it has a BMC156 instead of BMC150.

Im my opinion, adding type information to all of them would imply that
it can be used reliably, which is not the case unfortunately. Perhaps
I should instead add a comment to this enum to make this more clear?

What do you think?

Thanks!
Stephan

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0ad4bf37017621e25fe157fa095fd8849779a873
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c06a6aba6835946bcccb9909c98ec110949ea630