Message-ID: <20190316144814.0f8ddacf@archlinux>
Date:   Sat, 16 Mar 2019 14:48:37 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ibtsam Ul-Haq <ibtsam.haq.0x01@...il.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v2] iio: Add driver for TLA202x ADCs

On Wed, 13 Mar 2019 12:14:03 +0100
Ibtsam Ul-Haq <ibtsam.haq.0x01@...il.com> wrote:

> Basic driver for Texas Instruments TLA202x series ADCs. Input
> channels are configurable from the device tree. Input scaling
> is supported. Trigger buffer support is not yet implemented.
> 
> Signed-off-by: Ibtsam Ul-Haq <ibtsam.haq.0x01@...il.com>
One quick process thing - and this varies a bit by subsystem
so worth checking for each one what happened for previous drivers..

Please don't post new versions in replies to old threads.
They become buried in most email clients and it's not always
obvious whether different branches of the thread are talking
about particular versions of the driver.

Much better to just start a fresh thread and rely on the
consistent naming to make it obvious that it's a new version
of the same patch.

Anyhow, on to the review.

This needs a devicetree binding document.

Various minor bits inline.

Jonathan
> ---
> Changes in v2:
> - changed commit message
> - Added mutex to protect channel selection
> - Removed redundant mutex around i2c transfers
> - Removed PROCESSED channel output
> - Added SCALE info
> - Removed Continuous Mode since continuous read not supported
> - Removed SAMP_FREQ info since continuous read not supported
> ---
>  drivers/iio/adc/Kconfig      |  11 +
>  drivers/iio/adc/Makefile     |   1 +
>  drivers/iio/adc/ti-tla2024.c | 463 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 475 insertions(+)
>  create mode 100644 drivers/iio/adc/ti-tla2024.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 5762565..8c214c8 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -816,6 +816,17 @@ config TI_AM335X_ADC
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called ti_am335x_adc.
>  
> +config TI_TLA2024
> +	tristate "Texas Instruments TLA2024/TLA2022/TLA2021 ADC driver"
> +	depends on OF
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Texas Instruments TLA2024,
> +	  TLA2022 or TLA2021 I2C Analog to Digital Converters.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ti-tla2024.
> +
>  config TI_TLC4541
>  	tristate "Texas Instruments TLC4541 ADC driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 9874e05..819f35b 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
>  obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
>  obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
>  obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
> +obj-$(CONFIG_TI_TLA2024) += ti-tla2024.o
>  obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
>  obj-$(CONFIG_TWL6030_GPADC) += twl6030-gpadc.o
>  obj-$(CONFIG_VF610_ADC) += vf610_adc.o
> diff --git a/drivers/iio/adc/ti-tla2024.c b/drivers/iio/adc/ti-tla2024.c
> new file mode 100644
> index 0000000..e902eb8
> --- /dev/null
> +++ b/drivers/iio/adc/ti-tla2024.c
> @@ -0,0 +1,463 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Texas Instruments TLA2021/TLA2022/TLA2024 12-bit ADC driver
> + *
> + * Copyright (C) 2019 Koninklijke Philips N.V.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +
> +#define TLA2024_DATA 0x00
> +#define TLA2024_DATA_RES_MASK GENMASK(15, 4)
> +#define TLA2024_DATA_RES_SHIFT 4
> +
> +#define TLA2024_CONF 0x01
> +#define TLA2024_CONF_OS_MASK BIT(15)
> +#define TLA2024_CONF_OS_SHIFT 15
> +#define TLA2024_CONF_MUX_MASK GENMASK(14, 12)
> +#define TLA2024_CONF_MUX_SHIFT 12
> +#define TLA2024_CONF_PGA_MASK GENMASK(11, 9)
> +#define TLA2024_CONF_PGA_SHIFT 9
> +#define TLA2024_CONF_MODE_MASK BIT(8)
> +#define TLA2024_CONF_MODE_SHIFT 8
> +#define TLA2024_CONF_DR_MASK GENMASK(7, 5)
> +#define TLA2024_CONF_DR_SHIFT 5
> +
> +#define TLA2024_CONV_RETRY 10
> +
> +struct tla202x_model {
> +	unsigned int mux_available;
> +	unsigned int pga_available;
> +};
> +
> +struct tla2024 {
> +	struct i2c_client *i2c;
> +	struct tla202x_model *model;
> +	struct mutex lock; /* protect channel selection */
> +	u8 used_mux_channels;
> +};
> +
> +struct tla2024_channel {
> +	int ainp;
> +	int ainn;
> +	const char *datasheet_name;
> +	bool differential;
> +};
> +
> +static const struct tla2024_channel tla2024_all_channels[] = {
> +	{0, 1, "AIN0-AIN1", 1},
> +	{0, 3, "AIN0-AIN3", 1},
> +	{1, 3, "AIN1-AIN3", 1},
> +	{2, 3, "AIN2-AIN3", 1},
> +	{0, -1, "AIN0-GND", 0},

Single ended, so normal convention would just be AIN0

> +	{1, -1, "AIN1-GND", 0},
> +	{2, -1, "AIN2-GND", 0},
> +	{3, -1, "AIN3-GND", 0},
> +};
> +
> +static int tla2024_find_chan_idx(int ainp_in, int ainn_in, u16 *idx)
> +{
> +	u16 i;
> +
> +	for (i = 0; i < ARRAY_SIZE(tla2024_all_channels); i++) {
> +		if ((tla2024_all_channels[i].ainp == ainp_in) &&
> +		    (tla2024_all_channels[i].ainn == ainn_in)) {
> +			*idx = i;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +#define TLA202x_MODEL(_mux, _pga)		\
> +	{					\
> +		.mux_available = (_mux),	\
> +		.pga_available = (_pga),	\
> +	}
> +
> +enum tla2024_model_id {
> +	TLA2024 = 0,
> +	TLA2022 = 1,
> +	TLA2021 = 2,
> +};
> +
> +static struct tla202x_model tla202x_models[] = {
> +	TLA202x_MODEL(1, 1), // TLA2024
[TLA2024] = TLA202x_MODEL(1, 1), 

Makes it clear which is which and avoids the ugly c++ comments.

> +	TLA202x_MODEL(0, 1), // TLA2022
> +	TLA202x_MODEL(0, 0), // TLA2021
> +};
> +
> +static const int tla2024_scale[] = { /* scale, int plus micro */
> +	3, 0, 2, 0, 1, 0, 0, 500000, 0, 250000, 0, 125000 };
> +
> +static int tla2024_get(struct tla2024 *priv, u8 addr, u16 mask,
> +		       u16 shift, u16 *val)
> +{
> +	int ret;
> +	u16 data;
> +
> +	ret = i2c_smbus_read_word_swapped(priv->i2c, addr);
> +	if (ret < 0)
> +		return ret;
> +
> +	data = ret;
> +	*val = (mask & data) >> shift;
I'm going to guess that your shift is always just that needed
to move the mask to 0?  As such we have the really neat
FIELD_GET macros to avoid the need to pass both shifts and
masks around (it computes the shift from the mask).

> +
> +	return 0;
> +}
> +
> +static int tla2024_set(struct tla2024 *priv, u8 addr, u16 mask,
> +		       u16 shift, u16 val)
> +{
> +	int ret;
> +	u16 data;
> +
> +	ret = i2c_smbus_read_word_swapped(priv->i2c, addr);
> +	if (ret < 0)
> +		return ret;
> +
> +	data = ret;
> +	data &= ~mask;
> +	data |= mask & (val << shift);
> +
> +	ret = i2c_smbus_write_word_swapped(priv->i2c, addr, data);
> +
> +	return ret;
> +}
> +
> +static int tla2024_read_avail(struct iio_dev *idev,
> +			      struct iio_chan_spec const *chan,
> +			      const int **vals, int *type, int *length,
> +			      long mask)
> +{
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +
> +		*length = ARRAY_SIZE(tla2024_scale);
> +		*vals = tla2024_scale;
> +
> +		*type = IIO_VAL_INT_PLUS_MICRO;
> +		return IIO_AVAIL_LIST;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int tla2024_of_find_chan(struct tla2024 *priv, struct device_node *ch)
> +{
> +	u16 chan_idx = 0;
> +	u32 tmp_p, tmp_n;
> +	int ainp, ainn;
> +	int ret;
> +
> +	ret = of_property_read_u32_index(ch, "single-channel", 0, &tmp_p);

This property isn't currently in the dt docs (I think...)
Hence the generic binding doc needs amending.

> +	if (ret) {
> +		ret = of_property_read_u32_index(ch,
> +						 "diff-channels", 0, &tmp_p);
> +		if (ret)
> +			return ret;
> +
> +		ret = of_property_read_u32_index(ch,
> +						 "diff-channels", 1, &tmp_n);
> +		if (ret)
> +			return ret;
> +
> +		ainp = (int)tmp_p;
> +		ainn = (int)tmp_n;
> +	} else {
> +		ainp = (int)tmp_p;
> +		ainn = -1;

Given this value is 'magic' anyway just use MAX_UINT instead and avoid
the need for negative handling?  That gets rid of the need for tmp_p, tmp_n
above.

> +	}
> +
> +	ret = tla2024_find_chan_idx(ainp, ainn, &chan_idx);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* if model doesn"t have mux then only channel 0 is allowed */
> +	if (!priv->model->mux_available && chan_idx)
> +		return -EINVAL;
> +
> +	/* if already used */
> +	if ((priv->used_mux_channels) & (1 << chan_idx))
> +		return -EINVAL;
> +
> +	return chan_idx;
> +}
> +
> +static int tla2024_init_chan(struct iio_dev *idev, struct device_node *node,
> +			     struct iio_chan_spec *chan)
> +{
> +	struct tla2024 *priv = iio_priv(idev);
> +	u16 chan_idx;
> +	int ret;
> +
> +	ret = tla2024_of_find_chan(priv, node);
> +	if (ret < 0)
> +		return ret;
> +
> +	chan_idx = ret;
> +	priv->used_mux_channels |= BIT(chan_idx);
> +	chan->type = IIO_VOLTAGE;
> +	chan->channel = tla2024_all_channels[chan_idx].ainp;
> +	chan->channel2 = tla2024_all_channels[chan_idx].ainn;
> +	chan->differential = tla2024_all_channels[chan_idx].differential;
> +	chan->extend_name = node->name;
This is a bad idea.  You've just created a device specific userspace ABI
so all generic tools cannot be used.  What is the intended purpose of
doing this?

> +	chan->datasheet_name = tla2024_all_channels[chan_idx].datasheet_name;
> +	chan->indexed = 1;
> +	chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
> +	chan->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE);
> +	chan->info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SCALE);
> +
> +	return 0;
> +}
> +
> +static int tla2024_wait(struct tla2024 *priv)
> +{
> +	int ret;
> +	unsigned int retry = TLA2024_CONV_RETRY;
> +	u16 status;
> +
> +	do {
> +		if (!--retry)
> +			return -EIO;
> +		ret = tla2024_get(priv, TLA2024_CONF, TLA2024_CONF_OS_MASK,
> +				  TLA2024_CONF_OS_SHIFT, &status);
> +		if (ret < 0)
> +			return ret;
> +		if (!status)
> +			usleep_range(25, 1000);
> +	} while (!status);
> +
> +	return ret;
> +}
> +
> +static int tla2024_select_channel(struct tla2024 *priv,
> +				  struct iio_chan_spec const *chan)
> +{
> +	int ret;
> +	int ainp = chan->channel;
> +	int ainn = chan->channel2;
> +	u16 chan_id = 0;
> +
> +	ret = tla2024_find_chan_idx(ainp, ainn, &chan_id);
> +	if (ret < 0)
> +		return ret;
> +
> +	return tla2024_set(priv, TLA2024_CONF, TLA2024_CONF_MUX_MASK,
> +					   TLA2024_CONF_MUX_SHIFT, chan_id);
> +}
> +
> +static int tla2024_convert(struct tla2024 *priv)
> +{
> +	int ret = 0;
> +
> +	ret = tla2024_set(priv, TLA2024_CONF, TLA2024_CONF_OS_MASK,
> +			  TLA2024_CONF_OS_SHIFT, 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	return tla2024_wait(priv);
> +}
> +
> +static int tla2024_read_raw(struct iio_dev *idev,
> +			    struct iio_chan_spec const *channel, int *val,
> +			    int *val2, long mask)
> +{
> +	struct tla2024 *priv = iio_priv(idev);
> +	int ret;
> +	u16 data;
> +	s16 tmp;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&priv->lock);
> +		ret = tla2024_select_channel(priv, channel);
> +		if (ret < 0)
> +			goto return_unlock;
> +
> +		ret = tla2024_convert(priv);
> +		if (ret < 0)
> +			goto return_unlock;
> +
> +		ret = tla2024_get(priv, TLA2024_DATA, TLA2024_DATA_RES_MASK,
> +				  TLA2024_DATA_RES_SHIFT, &data);
> +		if (ret < 0)
> +			goto return_unlock;
> +
> +		tmp = (s16)(data << TLA2024_DATA_RES_SHIFT);
> +		*val = tmp >> TLA2024_DATA_RES_SHIFT;
> +		ret = IIO_VAL_INT;
> +
The moment we get a deeply indented goto target like this it
always suggests to me that we should consider pulling the code
being protected by the lock out to a separate function, leaving
the lock external so you can have a simple

lock
ret = functioncall
unlock
if (ret)... or just return ret;

> +return_unlock:
> +		mutex_unlock(&priv->lock);
> +		return ret;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		if (!(priv->model->pga_available)) {
> +			*val = 1; /* Scale always 1 mV when no PGA */
> +			return IIO_VAL_INT;
> +		}
> +		ret = tla2024_get(priv, TLA2024_CONF, TLA2024_CONF_PGA_MASK,
> +				  TLA2024_CONF_PGA_SHIFT, &data);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* gain for the 3bit pga values 6 and 7 is same as at 5 */
> +		if (data >= (ARRAY_SIZE(tla2024_scale) >> 1))
> +			data = (ARRAY_SIZE(tla2024_scale) >> 1) - 1;
> +
> +		*val = tla2024_scale[data << 1];
> +		*val2 = tla2024_scale[(data << 1) + 1];
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int tla2024_write_raw(struct iio_dev *idev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct tla2024 *priv = iio_priv(idev);
> +	int i;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		if (!(priv->model->pga_available))
> +			return -EINVAL; /* scale can't be changed if no pga */
> +
> +		for (i = 0; i < ARRAY_SIZE(tla2024_scale); i = i + 2) {
> +			if ((tla2024_scale[i] == val) &&
> +			    (tla2024_scale[i + 1] == val2))
> +				break;
> +		}
> +
> +		if (i == ARRAY_SIZE(tla2024_scale))
> +			return -EINVAL;
> +

This need a lock I think...

> +		return tla2024_set(priv, TLA2024_CONF, TLA2024_CONF_PGA_MASK,
> ++					TLA2024_CONF_PGA_SHIFT, i >> 1);
> +
> +	default:
> +		break;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int tla2024_of_chan_init(struct iio_dev *idev)
> +{
> +	struct device_node *node = idev->dev.of_node;
> +	struct device_node *child;
> +	struct iio_chan_spec *channels;
> +	int ret, i, num_channels;

> +
> +	num_channels = of_get_available_child_count(node);
> +	if (!num_channels) {
> +		dev_err(&idev->dev, "no channels configured\n");
> +		return -ENODEV;
> +	}
> +
> +	channels = devm_kcalloc(&idev->dev, num_channels,
> +				sizeof(struct iio_chan_spec), GFP_KERNEL);
> +	if (!channels)
> +		return -ENOMEM;
> +
> +	i = 0;
> +	for_each_available_child_of_node(node, child) {
> +		ret = tla2024_init_chan(idev, child, &channels[i]);
> +		if (ret) {
> +			of_node_put(child);
> +			return ret;
> +		}
> +		i++;
> +	}
> +
> +	idev->channels = channels;
> +	idev->num_channels = num_channels;
> +
> +	return 0;
> +}
> +
> +static const struct iio_info tla2024_info = {
> +	.read_raw = tla2024_read_raw,
> +	.write_raw = tla2024_write_raw,
> +	.read_avail = tla2024_read_avail,
> +};
> +
> +static int tla2024_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct iio_dev *iio;
> +	struct tla2024 *priv;
> +	struct tla202x_model *model;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WORD_DATA))
> +		return -EOPNOTSUPP;
> +
> +	model = &tla202x_models[id->driver_data];

What is the point in this local variable?  I would just
assign this directly below.

> +
> +	iio = devm_iio_device_alloc(&client->dev, sizeof(*priv));
> +	if (!iio)
> +		return -ENOMEM;
> +
> +	priv = iio_priv(iio);
> +	priv->i2c = client;
> +	priv->model = model;
> +	mutex_init(&priv->lock);
> +
> +	iio->dev.parent = &client->dev;
> +	iio->dev.of_node = client->dev.of_node;
> +	iio->name = client->name;
> +	iio->modes = INDIO_DIRECT_MODE;
> +	iio->info = &tla2024_info;
> +
> +	ret = tla2024_of_chan_init(iio);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = tla2024_set(priv, TLA2024_CONF, TLA2024_CONF_MODE_MASK,
> +			  TLA2024_CONF_MODE_SHIFT, 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	return devm_iio_device_register(&client->dev, iio);
> +}
> +
> +static const struct i2c_device_id tla2024_id[] = {
> +	{ "tla2024", TLA2024 },
> +	{ "tla2022", TLA2022 },
> +	{ "tla2021", TLA2021 },

Really minor point, but reverse numerical order is 'unusual'.. 

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, tla2024_id);
> +
> +static const struct of_device_id tla2024_of_match[] = {
> +	{ .compatible = "ti,tla2024" },
> +	{ .compatible = "ti,tla2022" },
> +	{ .compatible = "ti,tla2021" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, tla2024_of_match);
> +
> +static struct i2c_driver tla2024_driver = {
> +	.driver = {
> +		.name = "tla2024",
> +		.of_match_table = of_match_ptr(tla2024_of_match),
> +	},
> +	.probe = tla2024_probe,
> +	.id_table = tla2024_id,
> +};
> +module_i2c_driver(tla2024_driver);
> +
> +MODULE_AUTHOR("Ibtsam Haq <ibtsam.haq@...lips.com>");
> +MODULE_DESCRIPTION("Texas Instruments TLA2021/TLA2022/TLA2024 ADC driver");
> +MODULE_LICENSE("GPL v2");

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