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Date:   Sun, 19 Aug 2018 20:02:57 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Kent Gustavsson <kent@...oris.se>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/3] iio: adc: add support for mcp3911

On Wed,  8 Aug 2018 10:09:15 +0200
Marcus Folkesson <marcus.folkesson@...il.com> wrote:

> MCP3911 is a dual channel Analog Front End (AFE) containing two
> synchronous sampling delta-sigma Analog-to-Digital Converters (ADC).
> 
> Co-Developed-by: Kent Gustavsson <kent@...oris.se>
checkpatch points out..
Co-developed-by is the 'official' form of the tag. I'll fixup.
(first time I've seen one of these ;)

> Signed-off-by: Kent Gustavsson <kent@...oris.se>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
Applied to the togreg branch of iio.git and pushed out as testing for the
autobuilders to play with it. 

A few really trivial comments inline.  Also some slightly odd alignment
I'll fix up that I haven't noted, but not every parameter second line
lines up with the opening brackets correctly.

Jonathan

> ---
> 
> Notes:
>     v4:
>     	- remove defined(CONFIG_OF) and of_match_ptr() macro
>     	- do not check adc->clki as clock api is NULL-aware
>     	- add Kent as co-developer
>     v3:
>     	- rename adc_clk to clki
>     	- add error handling/cleanup for clock
>     v2:
>     	- cleanups and bugfixes (thanks Peter Meerwald-Stadler)
>     	- drop hardware gain
>     	- use the presence or lack of regulator to indicate if we go for internal or external voltage reference
>     	- do not store device node in private struct
>     	- drop support to set width in devicetree
>     	- use the presence or lack of clock to indicate if we go for internal or external clock
> 
>  drivers/iio/adc/Kconfig   |  10 ++
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/mcp3911.c | 361 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 372 insertions(+)
>  create mode 100644 drivers/iio/adc/mcp3911.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 15606f237480..f9a41fa96fcc 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -501,6 +501,16 @@ config MCP3422
>  	  This driver can also be built as a module. If so, the module will be
>  	  called mcp3422.
>  
> +config MCP3911
> +	tristate "Microchip Technology MCP3911 driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Microchip Technology's MCP3911
> +	  analog to digital converter.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called mcp3911.
> +
>  config MEDIATEK_MT6577_AUXADC
>          tristate "MediaTek AUXADC driver"
>          depends on ARCH_MEDIATEK || COMPILE_TEST
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 28a9423997f3..3cfebfff7d26 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_MAX1363) += max1363.o
>  obj-$(CONFIG_MAX9611) += max9611.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
> +obj-$(CONFIG_MCP3911) += mcp3911.o
>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
>  obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
>  obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> new file mode 100644
> index 000000000000..540c8fbcce89
> --- /dev/null
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -0,0 +1,361 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for Microchip MCP3911, Two-channel Analog Front End
> + *
> + * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@...il.com>
> + * Copyright (C) 2018 Kent Gustavsson <kent@...oris.se>
> + */
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#define MCP3911_REG_CHANNEL0		0x00
> +#define MCP3911_REG_CHANNEL1		0x03
> +#define MCP3911_REG_MOD			0x06
> +#define MCP3911_REG_PHASE		0x07
> +#define MCP3911_REG_GAIN		0x09
> +
> +#define MCP3911_REG_STATUSCOM		0x0a
> +#define MCP3911_STATUSCOM_CH1_24WIDTH	BIT(4)
> +#define MCP3911_STATUSCOM_CH0_24WIDTH	BIT(3)
> +#define MCP3911_STATUSCOM_EN_OFFCAL	BIT(2)
> +#define MCP3911_STATUSCOM_EN_GAINCAL	BIT(1)
> +
> +#define MCP3911_REG_CONFIG		0x0c
> +#define MCP3911_CONFIG_CLKEXT		BIT(1)
> +#define MCP3911_CONFIG_VREFEXT		BIT(2)
> +
> +#define MCP3911_REG_OFFCAL_CH0		0x0e
> +#define MCP3911_REG_GAINCAL_CH0		0x11
> +#define MCP3911_REG_OFFCAL_CH1		0x14
> +#define MCP3911_REG_GAINCAL_CH1		0x17
> +#define MCP3911_REG_VREFCAL		0x1a
> +
> +#define MCP3911_CHANNEL(x)		(MCP3911_REG_CHANNEL0 + x * 3)
> +#define MCP3911_OFFCAL(x)		(MCP3911_REG_OFFCAL_CH0 + x * 6)
> +
> +/* Internal voltage reference in uV */
> +#define MCP3911_INT_VREF_UV		1200000
> +
> +#define MCP3911_REG_READ(reg, id)	((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff)
> +#define MCP3911_REG_WRITE(reg, id)	((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff)
> +
> +#define MCP3911_NUM_CHANNELS		2
> +
> +struct mcp3911 {
> +	struct spi_device *spi;
> +	struct mutex lock;
> +	struct regulator *vref;
> +	struct clk *clki;
> +	u32 dev_addr;
> +};
> +
> +static int mcp3911_read(struct mcp3911 *adc, u8 reg, u32 *val, u8 len)
> +{
> +	int ret;
> +
> +	reg = MCP3911_REG_READ(reg, adc->dev_addr);
> +	ret = spi_write_then_read(adc->spi, &reg, 1, val, len);
> +	if (ret < 0)
> +		return ret;
> +
> +	be32_to_cpus(val);
> +	*val >>= ((4 - len) * 8);
> +	dev_dbg(&adc->spi->dev, "reading 0x%x from register 0x%x\n", *val,
> +			reg>>1);

Spaces around that >> preferred - I'll add them.

> +	return ret;
> +}
> +
> +static int mcp3911_write(struct mcp3911 *adc, u8 reg, u32 val, u8 len)
> +{
> +	dev_dbg(&adc->spi->dev, "writing 0x%x to register 0x%x\n", val, reg);
> +
> +	val <<= (3 - len) * 8;
> +	cpu_to_be32s(&val);
> +	val |= MCP3911_REG_WRITE(reg, adc->dev_addr);
> +
> +	return spi_write(adc->spi, &val, len + 1);
> +}
> +
> +static int mcp3911_update(struct mcp3911 *adc, u8 reg, u32 mask,
> +		u32 val, u8 len)
> +{
> +	u32 tmp;
> +	int ret;
> +
> +	ret = mcp3911_read(adc, reg, &tmp, len);
> +	if (ret)
> +		return ret;
> +
> +	val &= mask;
> +	val |= tmp & ~mask;
> +	return mcp3911_write(adc, reg, val, len);
> +}
> +
> +static int mcp3911_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *channel, int *val,
> +			    int *val2, long mask)
> +{
> +	struct mcp3911 *adc = iio_priv(indio_dev);
> +	int ret = -EINVAL;
> +
> +	mutex_lock(&adc->lock);
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = mcp3911_read(adc,
> +				MCP3911_CHANNEL(channel->channel), val, 3);
> +		if (ret)
> +			goto out;
> +
> +		ret = IIO_VAL_INT;
> +		break;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		ret = mcp3911_read(adc,
> +				MCP3911_OFFCAL(channel->channel), val, 3);
> +		if (ret)
> +			goto out;
> +
> +		ret = IIO_VAL_INT;
> +		break;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		if (adc->vref) {
> +			ret = regulator_get_voltage(adc->vref);
> +			if (ret < 0) {
> +				dev_err(indio_dev->dev.parent,
> +					"failed to get vref voltage: %d\n",
> +				       ret);
> +				goto out;
> +			}
> +
> +			*val = ret / 1000;
> +		} else {
> +			*val = MCP3911_INT_VREF_UV;
> +		}
> +
> +		*val2 = 24;
> +		ret = IIO_VAL_FRACTIONAL_LOG2;
> +		break;
> +	}
> +
> +out:
> +	mutex_unlock(&adc->lock);
> +	return ret;
> +}
> +
> +static int mcp3911_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *channel, int val,
> +			    int val2, long mask)
> +{
> +	struct mcp3911 *adc = iio_priv(indio_dev);
> +	int ret = -EINVAL;
> +
> +	mutex_lock(&adc->lock);
> +	switch (mask) {
> +	case IIO_CHAN_INFO_OFFSET:
> +		if (val2 != 0) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
Nitpick that I don't care about enough to delay on this.  Could have
moved the lock into the case statement then done the check outside the lock
which would have been slightly nicer.
> +
> +		/* Write offset */
> +		ret = mcp3911_write(adc, MCP3911_OFFCAL(channel->channel), val,
> +				3);
> +		if (ret)
> +			goto out;
> +
> +		/* Enable offset*/
> +		ret = mcp3911_update(adc, MCP3911_REG_STATUSCOM,
> +				MCP3911_STATUSCOM_EN_OFFCAL,
> +				MCP3911_STATUSCOM_EN_OFFCAL, 2);
> +		break;
> +	}
> +
> +out:
> +	mutex_unlock(&adc->lock);
> +	return ret;
> +}
> +
> +#define MCP3911_CHAN(idx) {					\
> +		.type = IIO_VOLTAGE,				\
> +		.indexed = 1,					\
> +		.channel = idx,					\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
> +			BIT(IIO_CHAN_INFO_OFFSET) |		\
> +			BIT(IIO_CHAN_INFO_SCALE),		\
> +}
> +
> +static const struct iio_chan_spec mcp3911_channels[] = {
> +	MCP3911_CHAN(0),
> +	MCP3911_CHAN(1),
> +};
> +
> +static const struct iio_info mcp3911_info = {
> +	.read_raw = mcp3911_read_raw,
> +	.write_raw = mcp3911_write_raw,
> +};
> +
> +static int mcp3911_config(struct mcp3911 *adc, struct device_node *of_node)
> +{
> +	u32 configreg;
> +	int ret;
> +
> +	of_property_read_u32(of_node, "device-addr", &adc->dev_addr);
> +	if (adc->dev_addr > 3) {
> +		dev_err(&adc->spi->dev,
> +				"invalid device address (%i). Must be in range 0-3.\n",
> +				adc->dev_addr);
> +		return -EINVAL;
> +	}
> +	dev_dbg(&adc->spi->dev, "use device address %i\n", adc->dev_addr);
> +
> +	ret = mcp3911_read(adc, MCP3911_REG_CONFIG, &configreg, 2);
> +	if (ret)
> +		return ret;
> +
> +	if (adc->vref) {
> +		dev_dbg(&adc->spi->dev, "use external voltage reference\n");
> +		configreg |= MCP3911_CONFIG_VREFEXT;
> +	} else {
> +		dev_dbg(&adc->spi->dev, "use internal voltage reference (1.2V)\n");
> +		configreg &= ~MCP3911_CONFIG_VREFEXT;
> +	}
> +
> +	if (adc->clki) {
> +		dev_dbg(&adc->spi->dev, "use external clock as clocksource\n");
> +		configreg |= MCP3911_CONFIG_CLKEXT;
> +	} else {
> +		dev_dbg(&adc->spi->dev, "use crystal oscillator as clocksource\n");
> +		configreg &= ~MCP3911_CONFIG_CLKEXT;
> +	}
> +
> +	return  mcp3911_write(adc, MCP3911_REG_CONFIG, configreg, 2);
> +}
> +
> +static int mcp3911_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct mcp3911 *adc;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	adc = iio_priv(indio_dev);
> +	adc->spi = spi;
> +
> +	adc->vref = devm_regulator_get_optional(&adc->spi->dev, "vref");
> +	if (IS_ERR(adc->vref)) {
> +		if (PTR_ERR(adc->vref) == -ENODEV) {
> +			adc->vref = NULL;
> +		} else {
> +			dev_err(&adc->spi->dev,
> +					"failed to get regulator (%ld)\n",
> +					PTR_ERR(adc->vref));
> +			return PTR_ERR(adc->vref);
> +		}
> +
> +	} else {
> +		ret = regulator_enable(adc->vref);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	adc->clki = devm_clk_get(&adc->spi->dev, NULL);
> +	if (IS_ERR(adc->clki)) {
> +		if (PTR_ERR(adc->clki) == -ENOENT) {
> +			adc->clki = NULL;
> +		} else {
> +			dev_err(&adc->spi->dev,
> +					"failed to get adc clk (%ld)\n",
> +					PTR_ERR(adc->clki));
> +			ret = PTR_ERR(adc->clki);
> +			goto reg_disable;
> +		}
> +	} else {
> +		ret = clk_prepare_enable(adc->clki);
> +		if (ret < 0) {
> +			dev_err(&adc->spi->dev,
> +				"Failed to enable clki: %d\n", ret);
> +			goto reg_disable;
> +		}
> +	}
> +
> +	ret = mcp3911_config(adc, spi->dev.of_node);
> +	if (ret)
> +		goto clk_disable;
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &mcp3911_info;
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	indio_dev->channels = mcp3911_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(mcp3911_channels);
> +
> +	mutex_init(&adc->lock);
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto clk_disable;
> +
> +	return ret;
> +
> +clk_disable:
> +	clk_disable_unprepare(adc->clki);
> +reg_disable:
> +	if (adc->vref)
> +		regulator_disable(adc->vref);
> +
> +	return ret;
> +}
> +
> +static int mcp3911_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct mcp3911 *adc = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	clk_disable_unprepare(adc->clki);
> +	if (adc->vref)
> +		regulator_disable(adc->vref);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id mcp3911_dt_ids[] = {
> +	{ .compatible = "microchip,mcp3911" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, mcp3911_dt_ids);
> +
> +static const struct spi_device_id mcp3911_id[] = {
> +	{ "mcp3911", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, mcp3911_id);
> +
> +static struct spi_driver mcp3911_driver = {
> +	.driver = {
> +		.name = "mcp3911",
> +		.of_match_table = mcp3911_dt_ids,
> +	},
> +	.probe = mcp3911_probe,
> +	.remove = mcp3911_remove,
> +	.id_table = mcp3911_id,
> +};
> +module_spi_driver(mcp3911_driver);
> +
> +MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@...il.com>");
> +MODULE_AUTHOR("Kent Gustavsson <kent@...oris.se>");
> +MODULE_DESCRIPTION("Microchip Technology MCP3911");
> +MODULE_LICENSE("GPL v2");

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