Re: [PATCH v3 2/3] iio: adc: tsc2046: add vref support

[Marco Felsch <m.felsch@pengutronix.de>]

Hi Oleksij,

sorry for jumping in, please see below.

On 22-09-01, Oleksij Rempel wrote:
> If VREF pin is attached, we should use external VREF source instead of
> the internal. Otherwise we will get wrong measurements on some of channel
> types.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  drivers/iio/adc/ti-tsc2046.c | 64 +++++++++++++++++++++++++++++++-----
>  1 file changed, 55 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-tsc2046.c b/drivers/iio/adc/ti-tsc2046.c
> index 0d9436a69cbfb..bbc8b4137b0b1 100644
> --- a/drivers/iio/adc/ti-tsc2046.c
> +++ b/drivers/iio/adc/ti-tsc2046.c
> @@ -8,6 +8,7 @@
>  #include <linux/bitfield.h>
>  #include <linux/delay.h>
>  #include <linux/module.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/spi/spi.h>
>  
>  #include <asm/unaligned.h>
> @@ -175,6 +176,9 @@ struct tsc2046_adc_priv {
>  	u32 time_per_bit_ns;
>  
>  	struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
> +	bool use_internal_vref;
> +	unsigned int vref_mv;

We wouldn't need those members if we just enable/disable the regulator
on demand. This would also be more power efficient.

> +	struct regulator *vref_reg;
>  };
>  
>  #define TI_TSC2046_V_CHAN(index, bits, name)			\
> @@ -252,7 +256,9 @@ static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
>  	case TI_TSC2046_ADDR_AUX:
>  	case TI_TSC2046_ADDR_VBAT:
>  	case TI_TSC2046_ADDR_TEMP0:
> -		pd |= TI_TSC2046_SER | TI_TSC2046_PD1_VREF_ON;
> +		pd |= TI_TSC2046_SER;
> +		if (priv->use_internal_vref)
> +			pd |= TI_TSC2046_PD1_VREF_ON;

Then this line would become:

+		if (!priv->vref_reg)
+			pd |= TI_TSC2046_PD1_VREF_ON;


>  	}
>  
>  	return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
> @@ -468,7 +474,7 @@ static int tsc2046_adc_read_raw(struct iio_dev *indio_dev,

This function needs to enable the vref_reg before the switch-case and
disable it afterwards.

>  		 * So, it is better to use external voltage-divider driver
>  		 * instead, which is calculating complete chain.
>  		 */
> -		*val = TI_TSC2046_INT_VREF;
> +		*val = priv->vref_mv;
>  		*val2 = chan->scan_type.realbits;
>  		return IIO_VAL_FRACTIONAL_LOG2;
>  	}
> @@ -781,22 +787,42 @@ static int tsc2046_adc_probe(struct spi_device *spi)
>  	indio_dev->num_channels = dcfg->num_channels;
>  	indio_dev->info = &tsc2046_adc_info;
>  
> +	priv->vref_reg = devm_regulator_get_optional(&spi->dev, "vref");

This line would be enough and we could drop

> +	if (!IS_ERR(priv->vref_reg)) {
> +		ret = regulator_enable(priv->vref_reg);
> +		if (ret)
> +			return ret;
> +
> +		ret = regulator_get_voltage(priv->vref_reg);
> +		if (ret < 0)
> +			goto err_regulator_disable;
> +
> +		priv->vref_mv = ret / 1000;
> +		priv->use_internal_vref = false;
> +	} else {
> +		/* Use internal reference */
> +		priv->vref_mv = TI_TSC2046_INT_VREF;
> +		priv->use_internal_vref = true;
> +	}
> +

this part.

>  	tsc2046_adc_parse_fwnode(priv);
>  
>  	ret = tsc2046_adc_setup_spi_msg(priv);
>  	if (ret)
> -		return ret;
> +		goto err_regulator_disable;
>  
>  	mutex_init(&priv->slock);
>  
>  	ret = devm_request_irq(dev, spi->irq, &tsc2046_adc_irq,
>  			       IRQF_NO_AUTOEN, indio_dev->name, indio_dev);
>  	if (ret)
> -		return ret;
> +		goto err_regulator_disable;
>  
>  	trig = devm_iio_trigger_alloc(dev, "touchscreen-%s", indio_dev->name);
> -	if (!trig)
> -		return -ENOMEM;
> +	if (!trig) {
> +		ret = -ENOMEM;
> +		goto err_regulator_disable;
> +	}
>  
>  	priv->trig = trig;
>  	iio_trigger_set_drvdata(trig, indio_dev);
> @@ -811,20 +837,39 @@ static int tsc2046_adc_probe(struct spi_device *spi)
>  	ret = devm_iio_trigger_register(dev, trig);
>  	if (ret) {
>  		dev_err(dev, "failed to register trigger\n");
> -		return ret;
> +		goto err_regulator_disable;
>  	}
>  
>  	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
>  					      &tsc2046_adc_trigger_handler, NULL);
>  	if (ret) {
>  		dev_err(dev, "Failed to setup triggered buffer\n");
> -		return ret;
> +		goto err_regulator_disable;
>  	}
>  
>  	/* set default trigger */
>  	indio_dev->trig = iio_trigger_get(priv->trig);
>  
> -	return devm_iio_device_register(dev, indio_dev);
> +	ret = devm_iio_device_register(dev, indio_dev);
> +	if (ret)
> +		goto err_regulator_disable;
> +
> +	return 0;
> +
> +err_regulator_disable:
> +	if (!IS_ERR(priv->vref_reg))
> +		regulator_disable(priv->vref_reg);
> +
> +	return ret;

As well as the whole new error handling and

> +}
> +
> +static void tsc2046_adc_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +
> +	if (!IS_ERR(priv->vref_reg))
> +		regulator_disable(priv->vref_reg);
>  }

the remove callback.

Regards,
  Marco

>  static const struct of_device_id ads7950_of_table[] = {
> @@ -839,6 +884,7 @@ static struct spi_driver tsc2046_adc_driver = {
>  		.of_match_table = ads7950_of_table,
>  	},
>  	.probe = tsc2046_adc_probe,
> +	.remove = tsc2046_adc_remove,
>  };
>  module_spi_driver(tsc2046_adc_driver);
>  
> -- 
> 2.30.2
> 
> 
>