Re: [PATCH 1/3] iio: adc: add ltc2309 support

[Liam Beguin <liambeguin@gmail.com>]

On Thu, Aug 24, 2023 at 08:00:11PM +0200, Krzysztof Kozlowski wrote:
> On 24/08/2023 18:55, Liam Beguin wrote:
> > The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> > 
> > This implements support for all single-ended and differential channels,
> > in unipolar mode only.
> > 
> > Signed-off-by: Liam Beguin <liambeguin@gmail.com>
> > ---
> >  drivers/iio/adc/Kconfig   |  10 ++
> >  drivers/iio/adc/Makefile  |   1 +
> >  drivers/iio/adc/ltc2309.c | 232 ++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 243 insertions(+)
> > 
> 
> 
> 
> > +static int ltc2309_read_raw(struct iio_dev *indio_dev,
> > +			    struct iio_chan_spec const *chan, int *val,
> > +			    int *val2, long mask)
> > +{
> > +	struct ltc2309 *ltc2309 = iio_priv(indio_dev);
> > +	u16 buf;
> > +	int ret;
> > +	u8 din;
> > +
> > +	mutex_lock(&ltc2309->lock);
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		din = FIELD_PREP(LTC2309_DIN_CH_MASK, chan->address & 0x0f) |
> > +			FIELD_PREP(LTC2309_DIN_UNI, 1) |
> > +			FIELD_PREP(LTC2309_DIN_SLEEP, 0);
> > +
> > +		ret = i2c_smbus_write_byte(ltc2309->client, din);
> > +		if (ret < 0) {
> > +			dev_err(ltc2309->dev, "i2c command failed: %pe\n",
> > +				ERR_PTR(ret));
> > +			goto out;
> > +		}
> > +
> > +		ret = i2c_master_recv(ltc2309->client, (char *)&buf, 2);
> > +		if (ret < 0) {
> > +			dev_err(ltc2309->dev, "i2c read failed: %pe\n",
> > +				ERR_PTR(ret));
> > +			goto out;
> > +		}
> > +
> > +		*val = be16_to_cpu(buf) >> 4;
> > +
> > +		ret = IIO_VAL_INT;
> > +		break;
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*val = ltc2309->vref_mv;
> > +		*val2 = LTC2309_ADC_RESOLUTION;
> > +		ret = IIO_VAL_FRACTIONAL_LOG2;
> 
> Why this case is in critical section?
> 

my bad, I'll reduce it to INFO_RAW.

> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +		break;
> > +	}
> > +
> > +out:
> > +	mutex_unlock(&ltc2309->lock);
> > +	return ret;
> > +}
> > +
> > +static const struct iio_info ltc2309_info = {
> > +	.read_raw = ltc2309_read_raw,
> > +};
> > +
> > +static int ltc2309_probe(struct i2c_client *client,
> > +			 const struct i2c_device_id *id)
> > +{
> > +	struct iio_dev *indio_dev;
> > +	struct ltc2309 *ltc2309;
> > +	int ret = 0;
> > +
> > +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
> > +	if (!indio_dev)
> > +		return -ENOMEM;
> > +
> > +	i2c_set_clientdata(client, indio_dev);
> > +
> > +	ltc2309 = iio_priv(indio_dev);
> > +	ltc2309->dev = &indio_dev->dev;
> > +	ltc2309->client = client;
> > +	ltc2309->vref_mv = 4096; /* Default to the internal ref */
> > +
> > +	indio_dev->name = DRIVER_NAME;
> > +	indio_dev->dev.parent = &client->dev;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = ltc2309_channels;
> > +	indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
> > +	indio_dev->info = &ltc2309_info;
> > +
> > +	ltc2309->refcomp = devm_regulator_get_optional(&client->dev, "refcomp");
> > +	if (!IS_ERR_OR_NULL(ltc2309->refcomp)) {
> > +		ret = regulator_enable(ltc2309->refcomp);
> > +		if (ret) {
> > +			dev_err(ltc2309->dev, "failed to enable REFCOMP\n");
> > +			return ret;
> > +		}
> > +
> > +		ret = regulator_get_voltage(ltc2309->refcomp);
> > +		if (ret < 0)
> 
> You have unbalanced regulator. Same in all further error paths.
> 

Right, will fix.

I was going to add an action with devm_add_action_or_reset(), and
noticed a lot of duplicate code adding a custom disable action. Does
adding something like this make sense?

-- >8 --

diff --git a/drivers/regulator/devres.c b/drivers/regulator/devres.c
index 90bb0d178885..ff94f35fad87 100644
--- a/drivers/regulator/devres.c
+++ b/drivers/regulator/devres.c
@@ -70,12 +70,17 @@ struct regulator *devm_regulator_get_exclusive(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_regulator_get_exclusive);

-static void regulator_action_disable(void *d)
+/**
+ * regulator_action_disable - Generic disable action for managed resource
+ * @d: regulator to disable
+ */
+void regulator_action_disable(void *d)
 {
 	struct regulator *r = (struct regulator *)d;

 	regulator_disable(r);
 }
+EXPORT_SYMBOL_GPL(regulator_action_disable);

 static int _devm_regulator_get_enable(struct device *dev, const char *id,
 				      int get_type)
diff --git a/include/linux/regulator/consumer.h b/include/linux/regulator/consumer.h
index 39b666b40ea6..4c018af5d008 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -207,6 +207,8 @@ struct regulator *__must_check regulator_get_optional(struct device *dev,
 						      const char *id);
 struct regulator *__must_check devm_regulator_get_optional(struct device *dev,
 							   const char *id);
+
+void regulator_action_disable(void *d);
 int devm_regulator_get_enable(struct device *dev, const char *id);
 int devm_regulator_get_enable_optional(struct device *dev, const char *id);
 void regulator_put(struct regulator *regulator);

-- >8 --

This would let consumers reuse it directly with something like:

	devm_add_action_or_reset(ltc2309->dev,
				 regulator_action_disable,
				 ltc2309->vref);


Maybe it should be a separate series, including the cleanup?

> > +			return ret;
> > +
> > +		ltc2309->vref_mv = ret / 1000;
> > +		if (ret)
> > +			return ret;

I just noticed this extra if. will remove too.

> > +	}
> > +
> > +	mutex_init(&ltc2309->lock);
> > +
> > +	return devm_iio_device_register(&client->dev, indio_dev);
> > +}
> > +
> 
> 
> Best regards,
> Krzysztof
> 

Thanks,
Liam