Message-ID: <20181216110448.725ed2e0@archlinux>
Date:   Sun, 16 Dec 2018 11:04:48 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Dan Murphy <dmurphy@...com>
Cc:     <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <robh+dt@...nel.org>
Subject: Re: [PATCH v2 2/4] iio: adc: Add the TI ads124s08 ADC code

On Tue, 11 Dec 2018 13:12:05 -0600
Dan Murphy <dmurphy@...com> wrote:

> Introduce the TI ADS124S08 and the ADS124S06 ADC
> devices from TI.  The ADS124S08 is the 12 channel ADC
> and the ADS124S06 is the 6 channel ADC device
> 
> These devices share a common datasheet:
> http://www.ti.com/lit/gpn/ads124s08
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>

Hi Dan,

Something a bit odd around the size of data in here. You seem to be
putting 24 bit data into an unsigned short (which I'm fairly sure is 16
bits here..) Also, alignment in the buffer should 'naturally aligned'
so you need to have the storage size at 32 bits.

A few other minor bits and pieces inline.

Thanks,

Jonathan
> ---
> 
> v2 - Removed the fill_noop call, updated probe to use device managed calls,
> removed regulator support, fixed the buffer to allow 64 bit timestamp, changed
> all the defines from S0X to S08, added an enum for the IDs and updated copyright
> header format.  I may have missed a few summary changes here but here is the
> review reference - https://lore.kernel.org/patchwork/patch/1021048/
> 
>  drivers/iio/adc/Kconfig        |  10 +
>  drivers/iio/adc/Makefile       |   1 +
>  drivers/iio/adc/ti-ads124s08.c | 375 +++++++++++++++++++++++++++++++++
>  3 files changed, 386 insertions(+)
>  create mode 100644 drivers/iio/adc/ti-ads124s08.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index a52fea8749a9..e8c5686e6716 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -887,6 +887,16 @@ config TI_ADS8688
>  	  This driver can also be built as a module. If so, the module will be
>  	  called ti-ads8688.
>  
> +config TI_ADS124S08
> +	tristate "Texas Instruments ADS124S08"
> +	depends on SPI && OF
> +	help
> +	  If you say yes here you get support for Texas Instruments ADS124S08
> +	  and ADS124S06 ADC chips
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called ti-ads124s08.
> +
>  config TI_AM335X_ADC
>  	tristate "TI's AM335X ADC driver"
>  	depends on MFD_TI_AM335X_TSCADC && HAS_DMA
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index a6e6a0b659e2..d70293abfdba 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -79,6 +79,7 @@ obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
>  obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
>  obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
>  obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
> +obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.o
>  obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
>  obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
>  obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
> diff --git a/drivers/iio/adc/ti-ads124s08.c b/drivers/iio/adc/ti-ads124s08.c
> new file mode 100644
> index 000000000000..328dfe330088
> --- /dev/null
> +++ b/drivers/iio/adc/ti-ads124s08.c
> @@ -0,0 +1,375 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* TI ADS124S0X chip family driver
> + * Copyright (C) 2018 Texas Instruments Incorporated - http://www.ti.com/
> + */
> +
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/sysfs.h>
> +
> +/* Commands */
> +#define ADS124S08_CMD_NOP	0x00
> +#define ADS124S08_CMD_WAKEUP	0x02
> +#define ADS124S08_CMD_PWRDWN	0x04
> +#define ADS124S08_CMD_RESET	0x06
> +#define ADS124S08_CMD_START	0x08
> +#define ADS124S08_CMD_STOP	0x0a
> +#define ADS124S08_CMD_SYOCAL	0x16
> +#define ADS124S08_CMD_SYGCAL	0x17
> +#define ADS124S08_CMD_SFOCAL	0x19
> +#define ADS124S08_CMD_RDATA	0x12
> +#define ADS124S08_CMD_RREG	0x20
> +#define ADS124S08_CMD_WREG	0x40
> +
> +/* Registers */
> +#define ADS124S08_ID_REG	0x00
> +#define ADS124S08_STATUS	0x01
> +#define ADS124S08_INPUT_MUX	0x02
> +#define ADS124S08_PGA		0x03
> +#define ADS124S08_DATA_RATE	0x04
> +#define ADS124S08_REF		0x05
> +#define ADS124S08_IDACMAG	0x06
> +#define ADS124S08_IDACMUX	0x07
> +#define ADS124S08_VBIAS		0x08
> +#define ADS124S08_SYS		0x09
> +#define ADS124S08_OFCAL0	0x0a
> +#define ADS124S08_OFCAL1	0x0b
> +#define ADS124S08_OFCAL2	0x0c
> +#define ADS124S08_FSCAL0	0x0d
> +#define ADS124S08_FSCAL1	0x0e
> +#define ADS124S08_FSCAL2	0x0f
> +#define ADS124S08_GPIODAT	0x10
> +#define ADS124S08_GPIOCON	0x11
> +
> +/* ADS124S0x common channels */
> +#define ADS124S08_AIN0		0x00
> +#define ADS124S08_AIN1		0x01
> +#define ADS124S08_AIN2		0x02
> +#define ADS124S08_AIN3		0x03
> +#define ADS124S08_AIN4		0x04
> +#define ADS124S08_AIN5		0x05
> +#define ADS124S08_AINCOM	0x0c
> +/* ADS124S08 only channels */
> +#define ADS124S08_AIN6		0x06
> +#define ADS124S08_AIN7		0x07
> +#define ADS124S08_AIN8		0x08
> +#define ADS124S08_AIN9		0x09
> +#define ADS124S08_AIN10		0x0a
> +#define ADS124S08_AIN11		0x0b
> +#define ADS124S08_MAX_CHANNELS	12
> +
> +#define ADS124S08_POS_MUX_SHIFT	0x04
> +#define ADS124S08_INT_REF		0x09
> +
> +#define ADS124S08_START_REG_MASK	0x1f
> +#define ADS124S08_NUM_BYTES_MASK	0x1f
> +
> +#define ADS124S08_START_CONV	0x01
> +#define ADS124S08_STOP_CONV	0x00
> +
> +enum ads124s_id {
> +	ADS124S08_ID,
> +	ADS124S06_ID,
> +};
> +
> +struct ads124s_chip_info {
> +	const struct iio_chan_spec *channels;
> +	unsigned int num_channels;
> +};
> +
> +struct ads124s_private {
> +	const struct ads124s_chip_info	*chip_info;
> +	struct gpio_desc *reset_gpio;
> +	struct spi_device *spi;
> +	struct mutex lock;
> +	u8 data[ADS124S08_MAX_CHANNELS] ____cacheline_aligned;
> +};
> +
> +#define ADS124S08_CHAN(index)					\
> +{								\
> +	.type = IIO_VOLTAGE,					\
> +	.indexed = 1,						\
> +	.channel = index,					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.scan_index = index,					\
> +	.scan_type = {						\
> +		.sign = 'u',					\
> +		.realbits = 24,					\
> +		.storagebits = 24,				\

Ah I'd missed this before.  Storage bits needs to be rounded
up to 32 bits.  So to nearest 'natural alignment'.  The reason is
that it makes life easier for userspace code.

Interestingly the code below seems to pack them at 16 bits...

> +		.endianness = IIO_BE,				\

May be true on the hardware, but your read function is converting
it to IIO_CPU.

> +	},							\
> +}
> +
> +static const struct iio_chan_spec ads124s06_channels[] = {
> +	ADS124S08_CHAN(0),
> +	ADS124S08_CHAN(1),
> +	ADS124S08_CHAN(2),
> +	ADS124S08_CHAN(3),
> +	ADS124S08_CHAN(4),
> +	ADS124S08_CHAN(5),
> +};
> +
> +static const struct iio_chan_spec ads124s08_channels[] = {
> +	ADS124S08_CHAN(0),
> +	ADS124S08_CHAN(1),
> +	ADS124S08_CHAN(2),
> +	ADS124S08_CHAN(3),
> +	ADS124S08_CHAN(4),
> +	ADS124S08_CHAN(5),
> +	ADS124S08_CHAN(6),
> +	ADS124S08_CHAN(7),
> +	ADS124S08_CHAN(8),
> +	ADS124S08_CHAN(9),
> +	ADS124S08_CHAN(10),
> +	ADS124S08_CHAN(11),
> +};
> +
> +static const struct ads124s_chip_info ads124s_chip_info_tbl[] = {
> +	[ADS124S08_ID] = {
> +		.channels = ads124s08_channels,
> +		.num_channels = ARRAY_SIZE(ads124s08_channels),
> +	},
> +	[ADS124S06_ID] = {
> +		.channels = ads124s06_channels,
> +		.num_channels = ARRAY_SIZE(ads124s06_channels),
> +	},
> +};
> +
> +static int ads124s_write_cmd(struct iio_dev *indio_dev, u8 command)
> +{
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +
> +	priv->data[0] = command;
> +
> +	return spi_write(priv->spi, &priv->data[0], 1);
> +}
> +
> +static int ads124s_write_reg(struct iio_dev *indio_dev, u8 reg, u8 data)
> +{
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +
> +	priv->data[0] = ADS124S08_CMD_WREG | reg;
> +	priv->data[1] = 0x0;
> +	priv->data[2] = data;
> +
> +	return spi_write(priv->spi, &priv->data[0], 3);
> +}
> +
> +static int ads124s_reset(struct iio_dev *indio_dev)
> +{
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +
> +	if (priv->reset_gpio) {
> +		gpiod_set_value(priv->reset_gpio, 0);
> +		udelay(200);
> +		gpiod_set_value(priv->reset_gpio, 1);
> +	} else {
> +		return ads124s_write_cmd(indio_dev, ADS124S08_CMD_RESET);
> +	}
> +
> +	return 0;
> +};
> +
> +static int ads124s_read(struct iio_dev *indio_dev, unsigned int chan)
> +{
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +	int ret;
> +	u32 tmp;
> +	struct spi_transfer t[] = {
> +		{
> +			.tx_buf = &priv->data[0],
> +			.len = 4,
> +			.cs_change = 1,
> +		}, {
> +			.tx_buf = &priv->data[1],
> +			.rx_buf = &priv->data[1],
> +			.len = 4,
> +		},
> +	};
> +
> +	priv->data[0] = ADS124S08_CMD_RDATA;
> +	memset(&priv->data[1], ADS124S08_CMD_NOP, sizeof(priv->data));
> +
> +	ret = spi_sync_transfer(priv->spi, t, ARRAY_SIZE(t));
> +	if (ret < 0)
> +		return ret;
> +
> +	tmp = priv->data[2] << 16 | priv->data[3] << 8 | priv->data[4];
> +
> +	return tmp;
> +}
> +
> +static int ads124s_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long m)
> +{
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&priv->lock);
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = ads124s_write_reg(indio_dev, ADS124S08_INPUT_MUX,
> +					chan->channel);
> +		if (ret) {
> +			dev_err(&priv->spi->dev, "Set ADC CH failed\n");
> +			goto out;
> +		}
> +
> +		ret = ads124s_write_cmd(indio_dev, ADS124S08_START_CONV);
> +		if (ret) {
> +			dev_err(&priv->spi->dev, "Start ADC converions failed\n");
> +			goto out;
> +		}
> +
> +		ret = ads124s_read(indio_dev, chan->channel);
> +		if (ret < 0) {
> +			dev_err(&priv->spi->dev, "Read ADC failed\n");
> +			goto out;
> +		} else
> +			*val = ret;
> +
> +		ret = ads124s_write_cmd(indio_dev, ADS124S08_STOP_CONV);
> +		if (ret) {
> +			dev_err(&priv->spi->dev, "Stop ADC converions failed\n");
> +			goto out;
> +		}
> +
> +		ret = IIO_VAL_INT;
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +out:
> +	mutex_unlock(&priv->lock);
> +	return ret;
> +}
> +
> +static const struct iio_info ads124s_info = {
> +	.read_raw = &ads124s_read_raw,
> +};
> +
> +static irqreturn_t ads124s_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct ads124s_private *priv = iio_priv(indio_dev);
> +	unsigned short buffer[ADS124S08_MAX_CHANNELS + sizeof(s64)/sizeof(short)];

Please uses the kernel's fixed width sizes for clarity.
u16, u32 etc.  Also is a short big enough given you have 24 bit channels?

> +	int scan_index, j = 0;
> +	int ret;
> +
> +	for_each_set_bit(scan_index, indio_dev->active_scan_mask,
> +			 indio_dev->masklength) {
> +		ret = ads124s_write_reg(indio_dev, ADS124S08_INPUT_MUX,
> +					scan_index);
> +		if (ret)
> +			dev_err(&priv->spi->dev, "Set ADC CH failed\n");
> +
> +		ret = ads124s_write_cmd(indio_dev, ADS124S08_START_CONV);
> +		if (ret)
> +			dev_err(&priv->spi->dev, "Start ADC converions failed\n");
> +
> +		buffer[j] = ads124s_read(indio_dev, scan_index);
> +		ret = ads124s_write_cmd(indio_dev, ADS124S08_STOP_CONV);
> +		if (ret)
> +			dev_err(&priv->spi->dev, "Stop ADC converions failed\n");
> +
> +		j++;
> +	}
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
> +			pf->timestamp);
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int ads124s_probe(struct spi_device *spi)
> +{
> +	struct ads124s_private *ads124s_priv;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*ads124s_priv));
> +	if (indio_dev == NULL)
> +		return -ENOMEM;
> +
> +	ads124s_priv = iio_priv(indio_dev);
> +
> +	ads124s_priv->reset_gpio = devm_gpiod_get_optional(&spi->dev,
> +						   "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(ads124s_priv->reset_gpio))
> +		dev_info(&spi->dev, "Reset GPIO not defined\n");
> +
> +	ads124s_priv->chip_info = &ads124s_chip_info_tbl[spi_get_device_id(spi)->driver_data];

This is a very long line and easily solved with a local variable for the
driver_data value. I don't mind the over long lines if breaking them up will
hurt readability but that isn't the case here.

> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	ads124s_priv->spi = spi;
> +
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ads124s_priv->chip_info->channels;
> +	indio_dev->num_channels = ads124s_priv->chip_info->num_channels;
> +	indio_dev->info = &ads124s_info;
> +
> +	mutex_init(&ads124s_priv->lock);
> +
> +	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev, NULL,
> +					      ads124s_trigger_handler, NULL);
> +	if (ret) {
> +		dev_err(&spi->dev, "iio triggered buffer setup failed\n");
> +		return ret;
> +	}
> +
> +	ads124s_reset(indio_dev);
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct spi_device_id ads124s_id[] = {
> +	{ "ads124s06", ADS124S06_ID },
> +	{ "ads124s08", ADS124S08_ID },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, ads124s_id);
> +
> +static const struct of_device_id ads124s_of_table[] = {
> +	{ .compatible = "ti,ads124s06" },
> +	{ .compatible = "ti,ads124s08" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, ads124s_of_table);
> +
> +static struct spi_driver ads124s_driver = {
> +	.driver = {
> +		.name	= "ads124s08",
> +		.of_match_table = ads124s_of_table,
> +	},
> +	.probe		= ads124s_probe,
> +	.id_table	= ads124s_id,
> +};
> +module_spi_driver(ads124s_driver);
> +
> +MODULE_AUTHOR("Dan Murphy <dmuprhy@...com>");
> +MODULE_DESCRIPTION("TI TI_ADS12S0X ADC");
> +MODULE_LICENSE("GPL v2");

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