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Date:   Sat, 1 Dec 2018 17:20:13 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Giuliano Belinassi <giuliano.belinassi@gmail.com>
Cc:     lars@metafoo.de, Michael.Hennerich@analog.com, knaack.h@gmx.de,
        pmeerw@pmeerw.net, gregkh@linuxfoundation.org,
        stefan.popa@analog.com, alexandru.Ardelean@analog.com,
        renatogeh@gmail.com, linux-iio@vger.kernel.org,
        devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
        kernel-usp@googlegroups.com
Subject: Re: [PATCH 2/2] staging: iio: ad7780: Moving ad7780 out of staging
Message-ID: <20181201172001.13b5f818@archlinux>
In-Reply-To: <7756c163cf97c02fac3349dc5e1fa943ed6cc5d1.1543428366.git.giuliano.belinassi@usp.br>
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        <7756c163cf97c02fac3349dc5e1fa943ed6cc5d1.1543428366.git.giuliano.belinassi@usp.br>
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On Wed, 28 Nov 2018 16:16:34 -0200
Giuliano Belinassi <giuliano.belinassi@gmail.com> wrote:

> Move ad7780 sigma-delta adc out of staging to the main tree
Please add a few details here on what the device is and what interfaces
are provided.  It's nice for anyone whose first encounter with this
driver is this patch (as they don't look at activity in staging).
> 
> Signed-off-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
> Signed-off-by: Renato Lui Geh <renatogeh@gmail.com>

Look pretty good.  A few small things inline once patch 1 is sorted.
I'd also see if you can get agreement for SPDX from one of the AD
reviewers (they are normally fine with this I think and can
go ask Michael if they want to be sure and Michael isn't following the
thread)

Note some of the comments are actually on patch 1 but visible here
when placed in the surrounding code.  I'll try to mention any in
that thread as well in a minute...


Jonathan

> ---
>  drivers/iio/adc/Kconfig          |  13 ++
>  drivers/iio/adc/Makefile         |   1 +
>  drivers/iio/adc/ad7780.c         | 347 +++++++++++++++++++++++++++++++
>  drivers/staging/iio/adc/Kconfig  |  13 --
>  drivers/staging/iio/adc/Makefile |   1 -
>  drivers/staging/iio/adc/ad7780.c | 347 -------------------------------
>  6 files changed, 361 insertions(+), 361 deletions(-)
>  create mode 100644 drivers/iio/adc/ad7780.c
>  delete mode 100644 drivers/staging/iio/adc/ad7780.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 575bf69fea57..e517425e364d 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -92,6 +92,19 @@ config AD7793
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called AD7793.
>  
> +config AD7780
> +	tristate "Analog Devices AD7780 and similar ADCs driver"
> +	depends on SPI
> +	depends on GPIOLIB || COMPILE_TEST
> +	select AD_SIGMA_DELTA
> +	help
> +	  Say yes here to build support for Analog Devices AD7170, AD7171,
> +	  AD7780 and AD7781 SPI analog to digital converters (ADC).
> +	  If unsure, say N (but it's safe to say "Y").
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad7780.
> +
>  config AD7887
>  	tristate "Analog Devices AD7887 ADC driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 91ba28aeb150..3301ca10b385 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -11,6 +11,7 @@ obj-$(CONFIG_AD7298) += ad7298.o
>  obj-$(CONFIG_AD7923) += ad7923.o
>  obj-$(CONFIG_AD7476) += ad7476.o
>  obj-$(CONFIG_AD7766) += ad7766.o
> +obj-$(CONFIG_AD7780) += ad7780.o
>  obj-$(CONFIG_AD7791) += ad7791.o
>  obj-$(CONFIG_AD7793) += ad7793.o
>  obj-$(CONFIG_AD7887) += ad7887.o
> diff --git a/drivers/iio/adc/ad7780.c b/drivers/iio/adc/ad7780.c
> new file mode 100644
> index 000000000000..05979a79fda3
> --- /dev/null
> +++ b/drivers/iio/adc/ad7780.c
> @@ -0,0 +1,347 @@
> +/*
> + * AD7170/AD7171 and AD7780/AD7781 SPI ADC driver
> + *
> + * Copyright 2011 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2.

Definitely time to look at moving to SPDX as various AD reviewers
looking at this anyway so should be fine to get their ack!

> + */
> +
> +#include <linux/interrupt.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/spi/spi.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/err.h>
> +#include <linux/sched.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/adc/ad_sigma_delta.h>
> +
> +#define AD7780_RDY		BIT(7)
> +#define AD7780_FILTER		BIT(6)
> +#define AD7780_ERR		BIT(5)
> +#define AD7780_ID1		BIT(4)
> +#define AD7780_ID0		BIT(3)
> +#define AD7780_GAIN		BIT(2)
> +#define AD7780_PAT1		BIT(1)
> +#define AD7780_PAT0		BIT(0)
> +
> +#define AD7780_PATTERN		(AD7780_PAT0)
> +#define AD7780_PATTERN_MASK	(AD7780_PAT0 | AD7780_PAT1)
> +
> +#define AD7170_PAT2		BIT(2)
> +
> +#define AD7170_PATTERN		(AD7780_PAT0 | AD7170_PAT2)
> +#define AD7170_PATTERN_MASK	(AD7780_PAT0 | AD7780_PAT1 | AD7170_PAT2)
> +
> +#define AD7780_GAIN_GPIO	0
> +#define AD7780_FILTER_GPIO	1
> +
> +#define AD7780_GAIN_MIDPOINT	64
> +#define AD7780_FILTER_MIDPOINT	13350
> +
> +struct ad7780_chip_info {
> +	struct iio_chan_spec	channel;
> +	unsigned int		pattern_mask;
> +	unsigned int		pattern;
> +	bool			is_ad778x;
> +};
> +
> +struct ad7780_state {
> +	const struct ad7780_chip_info	*chip_info;
> +	struct regulator		*reg;
> +	struct gpio_desc		*powerdown_gpio;
> +	struct gpio_desc		*gain_gpio;
> +	struct gpio_desc		*filter_gpio;
> +	unsigned int	gain;
> +
> +	struct ad_sigma_delta sd;
> +};
> +
> +enum ad7780_supported_device_ids {
> +	ID_AD7170,
> +	ID_AD7171,
> +	ID_AD7780,
> +	ID_AD7781,
> +};
> +
> +static struct ad7780_state *ad_sigma_delta_to_ad7780(struct ad_sigma_delta *sd)
> +{
> +	return container_of(sd, struct ad7780_state, sd);
> +}
> +
> +static int ad7780_set_mode(struct ad_sigma_delta *sigma_delta,
> +			   enum ad_sigma_delta_mode mode)
> +{
> +	struct ad7780_state *st = ad_sigma_delta_to_ad7780(sigma_delta);
> +	unsigned int val;
> +
> +	switch (mode) {
> +	case AD_SD_MODE_SINGLE:
> +	case AD_SD_MODE_CONTINUOUS:
> +		val = 1;
> +		break;
> +	default:
> +		val = 0;
> +		break;
> +	}
> +
> +	gpiod_set_value(st->powerdown_gpio, val);
> +
> +	return 0;
> +}
> +
> +static int ad7780_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val,
> +			   int *val2,
> +			   long m)
> +{
> +	struct ad7780_state *st = iio_priv(indio_dev);
> +	int voltage_uv;
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		return ad_sigma_delta_single_conversion(indio_dev, chan, val);
> +	case IIO_CHAN_INFO_SCALE:
> +		voltage_uv = regulator_get_voltage(st->reg);
> +		if (voltage_uv < 0)
> +			return voltage_uv;
> +		*val = (voltage_uv / 1000) * st->gain;
> +		*val2 = chan->scan_type.realbits - 1;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = -(1 << (chan->scan_type.realbits - 1));
> +		return IIO_VAL_INT;
> +	}

We should be able to read back the current sampling frequency as well
(from a cached value).

> +
> +	return -EINVAL;
> +}
> +
> +static int ad7780_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val,
> +			    int val2,
> +			    long m)
> +{
> +	struct ad7780_state *st = iio_priv(indio_dev);
> +	const struct ad7780_chip_info *chip_info = st->chip_info;
> +	int uvref, gain;
> +	unsigned int full_scale;
> +
> +	if (!chip_info->is_ad778x)
> +		return 0;
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_SCALE:
> +		if (val != 0)
> +			return -EINVAL;
> +
> +		uvref = regulator_get_voltage(st->reg);
> +
> +		if (uvref < 0)
> +			return uvref;
> +
> +		full_scale = 1 << (chip_info->channel.scan_type.realbits - 1);
> +		gain = DIV_ROUND_CLOSEST(uvref, full_scale);
> +		gain = DIV_ROUND_CLOSEST(gain, val2);
> +
> +		gpiod_set_value(st->gain_gpio, gain < AD7780_GAIN_MIDPOINT ? 0 : 1);
> +	break;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		if (val2 != 0)

It's a bit odd to do a combination of a precise match (nothing after decimal
point) but then use just a threshold for the integer part... 

If you are going to do block this then insist on a precise match for the
filter value below and provide an available attribute to give the two possible values.

> +			return -EINVAL;
> +
> +		gpiod_set_value(st->filter_gpio, val < AD7780_FILTER_MIDPOINT ? 0 : 1);
> +	break;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
> +				     unsigned int raw_sample)
> +{
> +	struct ad7780_state *st = ad_sigma_delta_to_ad7780(sigma_delta);
> +	const struct ad7780_chip_info *chip_info = st->chip_info;
> +	int val;
> +
> +	if ((raw_sample & AD7780_ERR) ||
> +	    ((raw_sample & chip_info->pattern_mask) != chip_info->pattern))
> +		return -EIO;
> +
> +	if (chip_info->is_ad778x) {
> +		val = raw_sample & AD7780_GAIN;
> +
> +		if (val != gpiod_get_value(st->gain_gpio))
> +			return -EIO;
> +
> +		if (val)
> +			st->gain = 1;
> +		else
> +			st->gain = 128;

There are outstanding comments on this code in patch 1, I won't comment on
it here.

> +	}
> +
> +	return 0;
> +}
> +
> +static const struct ad_sigma_delta_info ad7780_sigma_delta_info = {
> +	.set_mode = ad7780_set_mode,
> +	.postprocess_sample = ad7780_postprocess_sample,
> +	.has_registers = false,
> +};
> +
> +#define AD7170_CHANNEL(bits, wordsize) \
> +	AD_SD_CHANNEL_NO_SAMP_FREQ(1, 0, 0, bits, 32, wordsize - bits)
> +#define AD7780_CHANNEL(bits, wordsize) \
> +	AD_SD_CHANNEL_GAIN_FILTER(1, 0, 0, bits, 32, wordsize - bits)
> +
> +static const struct ad7780_chip_info ad7780_chip_info_tbl[] = {
> +	[ID_AD7170] = {
> +		.channel = AD7170_CHANNEL(12, 24),
> +		.pattern = AD7170_PATTERN,
> +		.pattern_mask = AD7170_PATTERN_MASK,
> +		.is_ad778x = false,
> +	},
> +	[ID_AD7171] = {
> +		.channel = AD7170_CHANNEL(16, 24),
> +		.pattern = AD7170_PATTERN,
> +		.pattern_mask = AD7170_PATTERN_MASK,
> +		.is_ad778x = false,
> +	},
> +	[ID_AD7780] = {
> +		.channel = AD7780_CHANNEL(24, 32),
> +		.pattern = AD7780_PATTERN,
> +		.pattern_mask = AD7780_PATTERN_MASK,
> +		.is_ad778x = true,
> +	},
> +	[ID_AD7781] = {
> +		.channel = AD7780_CHANNEL(20, 32),
> +		.pattern = AD7780_PATTERN,
> +		.pattern_mask = AD7780_PATTERN_MASK,
> +		.is_ad778x = true,
> +	},
> +};
> +
> +static const struct iio_info ad7780_info = {
> +	.read_raw = ad7780_read_raw,
> +	.write_raw = ad7780_write_raw,
> +};
> +
> +static int ad7780_probe(struct spi_device *spi)
> +{
> +	struct ad7780_state *st;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	st->gain = 1;
> +
> +	ad_sd_init(&st->sd, indio_dev, spi, &ad7780_sigma_delta_info);
> +
> +	st->reg = devm_regulator_get(&spi->dev, "avdd");
> +	if (IS_ERR(st->reg))
> +		return PTR_ERR(st->reg);
> +
> +	ret = regulator_enable(st->reg);

Hmm.  This is obviously not an actual bug, but from my 'obviously correct'
mental filter is tripping over the fact the remove ordering is not
the precise opposite of the probe order.  As devm managed cleanup occurs
after remove finishes, the two gpios below are freed after the regulator
disable, whereas for precise reverse order they would be before it.

The easiest 'fix' for this would be to just move this regulator enable
until after we have grabbed the gpios.  I don't think that makes any
real difference as we use neither of them in this function anyway.

Another option would be to use devm_add_action_or_reset to do
the unwinding of this regulator_enable so that it gets cleaned up
in the devm unwind rather than by hand.

> +	if (ret) {
> +		dev_err(&spi->dev, "Failed to enable specified AVdd supply\n");
> +		return ret;
> +	}
> +
> +	st->chip_info =
> +		&ad7780_chip_info_tbl[spi_get_device_id(spi)->driver_data];
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = &st->chip_info->channel;
> +	indio_dev->num_channels = 1;
> +	indio_dev->info = &ad7780_info;
> +
> +	st->powerdown_gpio = devm_gpiod_get_optional(&spi->dev,
> +						     "powerdown",
> +						     GPIOD_OUT_LOW);
> +	if (IS_ERR(st->powerdown_gpio)) {
> +		ret = PTR_ERR(st->powerdown_gpio);
> +		dev_err(&spi->dev, "Failed to request powerdown GPIO: %d\n",
> +			ret);
> +		goto error_disable_reg;
> +	}
> +
> +	if (st->chip_info->is_ad778x) {
> +		st->gain_gpio = devm_gpiod_get_optional(&spi->dev,
> +							"gain",
> +							GPIOD_OUT_HIGH);
> +		if (IS_ERR(st->gain_gpio)) {
> +			ret = PTR_ERR(st->gain_gpio);
> +			dev_err(&spi->dev, "Failed to request gain GPIO: %d\n",
> +				ret);
> +			goto error_disable_reg;
> +		}
> +	}
> +
> +	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
> +	if (ret)
> +		goto error_disable_reg;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto error_cleanup_buffer_and_trigger;
> +
> +	return 0;
> +
> +error_cleanup_buffer_and_trigger:
> +	ad_sd_cleanup_buffer_and_trigger(indio_dev);
> +error_disable_reg:
> +	regulator_disable(st->reg);
> +
> +	return ret;
> +}
> +
> +static int ad7780_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct ad7780_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	ad_sd_cleanup_buffer_and_trigger(indio_dev);
> +
> +	regulator_disable(st->reg);
> +
> +	return 0;
> +}
> +
> +static const struct spi_device_id ad7780_id[] = {
> +	{"ad7170", ID_AD7170},
> +	{"ad7171", ID_AD7171},
> +	{"ad7780", ID_AD7780},
> +	{"ad7781", ID_AD7781},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, ad7780_id);
> +
> +static struct spi_driver ad7780_driver = {
> +	.driver = {
> +		.name	= "ad7780",
> +	},
> +	.probe		= ad7780_probe,
> +	.remove		= ad7780_remove,
> +	.id_table	= ad7780_id,
> +};
> +module_spi_driver(ad7780_driver);
> +
> +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
> +MODULE_DESCRIPTION("Analog Devices AD7780 and similar ADCs");
> +MODULE_LICENSE("GPL v2");

<cut removed code>