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Message-ID: <20210717183437.4d183037@jic23-huawei>
Date: Sat, 17 Jul 2021 18:34:37 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Liam Beguin <liambeguin@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com,
charles-antoine.couret@...ensium.com, Nuno.Sa@...log.com,
linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: Re: [PATCH v3 3/4] iio: adc: ad7949: add support for internal vref
On Tue, 13 Jul 2021 00:34:24 -0400
Liam Beguin <liambeguin@...il.com> wrote:
> From: Liam Beguin <lvb@...hos.com>
>
> Add support for selecting a custom reference voltage from the
> devicetree. If an external source is used, a vref regulator should be
> defined in the devicetree.
>
> Signed-off-by: Liam Beguin <lvb@...hos.com>
Hi Liam,
A few minor things inline.
Jonathan
> ---
> drivers/iio/adc/ad7949.c | 133 +++++++++++++++++++++++++++++++++------
> 1 file changed, 115 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index 65f78751225b..8b78da7ead36 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -36,7 +36,11 @@
>
> /* REF: reference/buffer selection */
> #define AD7949_CFG_BIT_REF GENMASK(5, 3)
> -#define AD7949_CFG_VAL_REF_EXT_BUF 7
> +#define AD7949_CFG_VAL_REF_EXT_TEMP_BUF 3
> +#define AD7949_CFG_VAL_REF_EXT_TEMP 2
> +#define AD7949_CFG_VAL_REF_INT_4096 1
> +#define AD7949_CFG_VAL_REF_INT_2500 0
> +#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)
>
> /* SEQ: channel sequencer. Allows for scanning channels */
> #define AD7949_CFG_BIT_SEQ GENMASK(2, 1)
> @@ -61,6 +65,14 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
> [ID_AD7689] = { .num_channels = 8, .resolution = 16 },
> };
>
> +/**
> + * struct ad7949_channel - ADC Channel parameters
> + * @refsel: reference selection
> + */
> +struct ad7949_channel {
> + u32 refsel;
> +};
> +
> /**
> * struct ad7949_adc_chip - AD ADC chip
> * @lock: protects write sequences
> @@ -78,6 +90,7 @@ struct ad7949_adc_chip {
> struct regulator *vref;
> struct iio_dev *indio_dev;
> struct spi_device *spi;
> + struct ad7949_channel *channels;
> u8 resolution;
> u8 bits_per_word;
> u16 cfg;
> @@ -138,6 +151,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> int i;
> u8 buf8[2];
> struct spi_message msg;
> + struct ad7949_channel ad7949_chan = ad7949_adc->channels[channel];
Better to use a pointer rather than copying the data.
> struct spi_transfer tx[] = {
> {
> .rx_buf = &ad7949_adc->buffer,
> @@ -154,8 +168,9 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> */
> for (i = 0; i < 2; i++) {
> ret = ad7949_spi_write_cfg(ad7949_adc,
> - FIELD_PREP(AD7949_CFG_BIT_INX, channel),
> - AD7949_CFG_BIT_INX);
> + FIELD_PREP(AD7949_CFG_BIT_INX, channel) |
> + FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_chan.refsel),
> + AD7949_CFG_BIT_INX | AD7949_CFG_BIT_REF);
> if (ret)
> return ret;
> if (channel == ad7949_adc->current_channel)
> @@ -225,6 +240,7 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
> int *val, int *val2, long mask)
> {
> struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
> + struct ad7949_channel ad7949_chan = ad7949_adc->channels[chan->channel];
> int ret;
>
> if (!val)
> @@ -242,12 +258,26 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
> return IIO_VAL_INT;
>
> case IIO_CHAN_INFO_SCALE:
> - ret = regulator_get_voltage(ad7949_adc->vref);
> - if (ret < 0)
> - return ret;
> + switch (ad7949_chan.refsel) {
> + case AD7949_CFG_VAL_REF_INT_2500:
> + *val = 2500;
> + break;
> + case AD7949_CFG_VAL_REF_INT_4096:
> + *val = 4096;
> + break;
> + case AD7949_CFG_VAL_REF_EXT_TEMP:
> + case AD7949_CFG_VAL_REF_EXT_TEMP_BUF:
> + ret = regulator_get_voltage(ad7949_adc->vref);
> + if (ret < 0)
> + return ret;
> +
> + /* convert value back to mV */
> + *val = ret / 1000;
> + break;
> + }
>
> - *val = ret / 5000;
> - return IIO_VAL_INT;
> + *val2 = (1 << ad7949_adc->resolution) - 1;
> + return IIO_VAL_FRACTIONAL;
> }
>
> return -EINVAL;
> @@ -286,7 +316,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> FIELD_PREP(AD7949_CFG_BIT_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
> FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc->current_channel) |
> FIELD_PREP(AD7949_CFG_BIT_BW_FULL, 1) |
> - FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_CFG_VAL_REF_EXT_BUF) |
> + FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->channels[0].refsel) |
> FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
> FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
>
> @@ -302,14 +332,24 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> return ret;
> }
>
> +static void ad7949_disable_reg(void *reg)
> +{
> + regulator_disable(reg);
> +}
> +
> static int ad7949_spi_probe(struct spi_device *spi)
> {
> u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
> struct device *dev = &spi->dev;
> const struct ad7949_adc_spec *spec;
> struct ad7949_adc_chip *ad7949_adc;
> + struct ad7949_channel *ad7949_chan;
> + struct device_node *child;
> struct iio_dev *indio_dev;
> + int mode;
> + u32 tmp;
> int ret;
> + int i;
>
> indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
> if (!indio_dev) {
> @@ -343,16 +383,75 @@ static int ad7949_spi_probe(struct spi_device *spi)
> return -EINVAL;
> }
>
> - ad7949_adc->vref = devm_regulator_get(dev, "vref");
> + /* Setup external voltage ref, buffered? */
> + ad7949_adc->vref = devm_regulator_get(dev, "vrefin");
> if (IS_ERR(ad7949_adc->vref)) {
> - dev_err(dev, "fail to request regulator\n");
> - return PTR_ERR(ad7949_adc->vref);
> + /* unbuffered? */
> + ad7949_adc->vref = devm_regulator_get(dev, "vref");
> + if (IS_ERR(ad7949_adc->vref)) {
> + /* Internal then */
> + mode = AD7949_CFG_VAL_REF_INT_4096;
> + }
> + mode = AD7949_CFG_VAL_REF_EXT_TEMP;
> }
> + mode = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;
>
> - ret = regulator_enable(ad7949_adc->vref);
> - if (ret < 0) {
> - dev_err(dev, "fail to enable regulator\n");
> - return ret;
> + if (mode > AD7949_CFG_VAL_REF_INT_4096) {
Range checks on enum values are always rather messy. So
better to explicitly match the cases that matter.
> + ret = regulator_enable(ad7949_adc->vref);
> + if (ret < 0) {
> + dev_err(dev, "fail to enable regulator\n");
> + return ret;
> + }
> +
> + ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
> + ad7949_adc->vref);
> + if (ret)
> + return ret;
> + }
> +
> + ad7949_adc->channels = devm_kcalloc(dev, spec->num_channels,
> + sizeof(*ad7949_adc->channels),
> + GFP_KERNEL);
> + if (!ad7949_adc->channels) {
> + dev_err(dev, "unable to allocate ADC channels\n");
> + return -ENOMEM;
> + }
> +
> + /* Initialize all channel structures */
> + for (i = 0; i < spec->num_channels; i++) {
> + ad7949_adc->channels[i].refsel = mode;
Kernel style is no brackets when only one item in a block.
> + }
> +
> + /* Read channel specific information form the devicetree */
> + for_each_child_of_node(dev->of_node, child) {
> + ret = of_property_read_u32(child, "reg", &i);
> + if (ret) {
> + dev_err(dev, "missing reg property in child: %s\n",
> + child->full_name);
> + of_node_put(child);
> + return ret;
> + }
> +
> + ad7949_chan = &ad7949_adc->channels[i];
> +
> + ret = of_property_read_u32(child, "adi,internal-ref-mv", &tmp);
Preference for generic device firmware properties not of_* specific ones.
I think there is nothing stopping this driver being probed from ACPI via PRP0001
before this change. Note you'll also need fwnode_for_each_child_node() above.
> + if (ret < 0 && ret != -EINVAL) {
> + of_node_put(child);
> + return ret;
> + }
> +
> + switch (tmp) {
> + case 2500:
> + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_2500;
> + break;
> + case 4096:
> + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_4096;
> + break;
> + default:
> + dev_err(dev, "unsupported internal voltage reference\n");
> + of_node_put(child);
> + return -EINVAL;
> + }
> }
>
> mutex_init(&ad7949_adc->lock);
> @@ -373,7 +472,6 @@ static int ad7949_spi_probe(struct spi_device *spi)
>
> err:
> mutex_destroy(&ad7949_adc->lock);
> - regulator_disable(ad7949_adc->vref);
>
> return ret;
> }
> @@ -385,7 +483,6 @@ static int ad7949_spi_remove(struct spi_device *spi)
>
> iio_device_unregister(indio_dev);
> mutex_destroy(&ad7949_adc->lock);
> - regulator_disable(ad7949_adc->vref);
Given mutex_destroy is mostly pointless (and definitely is here) that
leaves us with just iio_device_register(). Hence if you could do
a follow up patch finishing conversion of this to entirely devm managed
that would be a nice addition to this series (or separate patch is fine as well).
>
> return 0;
> }
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