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Date: Thu, 1 Sep 2022 10:24:25 +0200
From: Marco Felsch <m.felsch@...gutronix.de>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Jonathan Cameron <jic23@...nel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org,
Andy Shevchenko <andy.shevchenko@...il.com>,
kernel@...gutronix.de
Subject: Re: [PATCH v3 2/3] iio: adc: tsc2046: add vref support
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@...gutronix.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
>
>
>
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