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Date:   Sat, 18 Jan 2020 14:53:18 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Andreas Kemnade <andreas@kemnade.info>
Cc:     knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net,
        lee.jones@linaro.org, b.galvani@gmail.com,
        linus.walleij@linaro.org, linux-kernel@vger.kernel.org,
        linux-iio@vger.kernel.org, phh@phh.me, stefan@agner.ch,
        letux-kernel@openphoenux.org
Subject: Re: [PATCH 3/5] iio: adc: rn5t618: Add ADC driver for
 RN5T618/RC5T619
Message-ID: <20200118145318.399e8318@archlinux>
In-Reply-To: <20200117215926.15194-4-andreas@kemnade.info>
References: <20200117215926.15194-1-andreas@kemnade.info>
        <20200117215926.15194-4-andreas@kemnade.info>
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On Fri, 17 Jan 2020 22:59:24 +0100
Andreas Kemnade <andreas@kemnade.info> wrote:

> Both chips have an A/D converter capable of measuring
> things like VBAT, VUSB and analog inputs.
> 
> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
A few comments inline, but looks pretty good on the whole.

Jonathan

> ---
>  drivers/iio/adc/Kconfig       |  10 ++
>  drivers/iio/adc/Makefile      |   1 +
>  drivers/iio/adc/rn5t618-adc.c | 266 ++++++++++++++++++++++++++++++++++
>  3 files changed, 277 insertions(+)
>  create mode 100644 drivers/iio/adc/rn5t618-adc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index f0af3a42f53c..9ea9489e3f0a 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -735,6 +735,16 @@ config RCAR_GYRO_ADC
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called rcar-gyroadc.
>  
> +config RN5T618_ADC
> +	tristate "ADC for the RN5T618/RC5T619 family of chips"
> +	depends on MFD_RN5T618
> +	help
> +	  Say yes here to build support for the integrated ADC inside the
> +	  RN5T618/619 series PMICs:
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rn5t618-adc.
> +
>  config ROCKCHIP_SARADC
>  	tristate "Rockchip SARADC driver"
>  	depends on ARCH_ROCKCHIP || (ARM && COMPILE_TEST)
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index ef9cc485fb67..2aea70556ed0 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -69,6 +69,7 @@ obj-$(CONFIG_QCOM_VADC_COMMON) += qcom-vadc-common.o
>  obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
>  obj-$(CONFIG_QCOM_PM8XXX_XOADC) += qcom-pm8xxx-xoadc.o
>  obj-$(CONFIG_RCAR_GYRO_ADC) += rcar-gyroadc.o
> +obj-$(CONFIG_RN5T618_ADC) += rn5t618-adc.o
>  obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
>  obj-$(CONFIG_SC27XX_ADC) += sc27xx_adc.o
>  obj-$(CONFIG_SPEAR_ADC) += spear_adc.o
> diff --git a/drivers/iio/adc/rn5t618-adc.c b/drivers/iio/adc/rn5t618-adc.c
> new file mode 100644
> index 000000000000..81f872a7ad7f
> --- /dev/null
> +++ b/drivers/iio/adc/rn5t618-adc.c
> @@ -0,0 +1,266 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * ADC driver for the RICOH RN5T618 power management chip family
> + *
> + * Copyright (C) 2019 Andreas Kemnade
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/interrupt.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/mfd/rn5t618.h>
> +#include <linux/platform_device.h>
> +#include <linux/completion.h>
> +#include <linux/regmap.h>
> +#include <linux/iio/iio.h>
> +#include <linux/slab.h>
> +#include <linux/irqdomain.h>
> +
> +#define RN5T618_ADC_CONVERSION_TIMEOUT   (msecs_to_jiffies(500))
> +#define REFERENCE_VOLT 2500
> +
> +/* mask for selecting channels for single conversion */
> +#define ADCCNT3_CHANNEL_MASK 0x7
> +/* average 4-time conversion mode */
> +#define ADCCNT3_AVG BIT(3)
> +/* set for starting a single conversion, gets cleared by hw when done */
> +#define ADCCNT3_GODONE BIT(4)
> +/* automatic conversion, period is in ADCCNT2, selected channels are
> + * in ADCCNT1
> + */
> +#define ADCCNT3_AUTO BIT(5)
> +#define ADCEND_IRQ BIT(0)
> +
> +struct rn5t618_adc_data {
> +	struct device *dev;
> +	struct rn5t618 *rn5t618;
> +	struct completion conv_completion;
> +	int irq;
> +};
> +
> +struct rn5t618_channel_ratios {
> +	u16 numerator;
> +	u16 denominator;
> +};
> +
> +static const struct rn5t618_channel_ratios rn5t618_ratios[8] = {
> +	{50, 32}, /* LIMMON measured across 20mOhm, amplified by 32 */
Define an enum for the channel.  Then you can use explicit element
setting to make this code self docuemnting.

[LIMMON] = {50, 32},
[VBAT] = {2, 1}, etc.

Use the enum to fill in the channel numbers below as well and
it all becomes 'obviously' correct rather than having to check the
two things are in the same order.

> +	{2, 1}, /* VBAT */
> +	{3, 1}, /* VADP */
> +	{3, 1}, /* VUSB */
> +	{3, 1}, /* VSYS */
> +	{1, 1}, /* VTHM */
> +	{1, 1}, /* AIN1 */
> +	{1, 1}, /* AIN0 */
> +};
> +
> +static int rn5t618_read_adc_reg(struct rn5t618 *rn5t618, int reg, u16 *val)
> +{
> +	unsigned int h;
> +	unsigned int l;
> +	int ret;
> +
> +	ret = regmap_read(rn5t618->regmap, reg, &h);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = regmap_read(rn5t618->regmap, reg + 1, &l);
> +	if (ret < 0)
> +		return ret;

regmap_bulk_read perhaps? 

> +
> +	h <<= 4;
> +	h |= (l & 0xF);
> +	h &= 0xFFF;

I'd mask h before the shift.  More readable I think than
masking the l part twice.

> +	*val = h;
> +
> +	return 0;
> +}
> +
> +static irqreturn_t rn5t618_adc_irq(int irq, void *data)
> +{
> +	struct rn5t618_adc_data *adc = data;
> +	unsigned int r = 0;
> +	int ret;
> +
> +	/* clear low & high threshold irqs */
> +	regmap_write(adc->rn5t618->regmap, RN5T618_IR_ADC1, 0);
> +	regmap_write(adc->rn5t618->regmap, RN5T618_IR_ADC2, 0);
> +
> +	ret = regmap_read(adc->rn5t618->regmap, RN5T618_IR_ADC3, &r);
> +	if (ret < 0)
> +		dev_err(adc->dev, "failed to read IRQ status: %d\n", ret);
> +
> +	regmap_write(adc->rn5t618->regmap, RN5T618_IR_ADC3, 0);
> +
> +	if (r & ADCEND_IRQ)
> +		complete(&adc->conv_completion);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int rn5t618_adc_read(struct iio_dev *iio_dev,
> +			    const struct iio_chan_spec *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct rn5t618_adc_data *adc = iio_priv(iio_dev);
> +	u16 raw;
> +	int ret;
> +
> +	/* select channel */
> +	ret = regmap_update_bits(adc->rn5t618->regmap, RN5T618_ADCCNT3,
> +				 ADCCNT3_CHANNEL_MASK,
> +				 chan->channel);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = regmap_write(adc->rn5t618->regmap, RN5T618_EN_ADCIR3, ADCEND_IRQ);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = regmap_update_bits(adc->rn5t618->regmap, RN5T618_ADCCNT3,
> +				 ADCCNT3_AVG,
> +				 mask == IIO_CHAN_INFO_AVERAGE_RAW ?
> +				 ADCCNT3_AVG : 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	init_completion(&adc->conv_completion);
> +	/* single conversion */
> +	ret = regmap_update_bits(adc->rn5t618->regmap, RN5T618_ADCCNT3,
> +				 ADCCNT3_GODONE, ADCCNT3_GODONE);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = wait_for_completion_timeout(&adc->conv_completion,
> +					  RN5T618_ADC_CONVERSION_TIMEOUT);
> +	if (ret == 0) {
> +		dev_warn(adc->dev, "timeout waiting for adc result\n");
> +		return -ETIMEDOUT;
> +	}
> +
> +	ret = rn5t618_read_adc_reg(adc->rn5t618,
> +				   RN5T618_ILIMDATAH + 2 * chan->channel,
> +				   &raw);
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = raw;
> +	if (mask == IIO_CHAN_INFO_PROCESSED)
> +		*val = *val * REFERENCE_VOLT *
> +		       rn5t618_ratios[chan->channel].numerator /
> +		       rn5t618_ratios[chan->channel].denominator / 4095;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static const struct iio_info rn5t618_adc_iio_info = {
> +	.read_raw = &rn5t618_adc_read,
> +};
> +
> +#define RN5T618_ADC_CHANNEL(_channel, _type, _name) { \
> +	.type = _type, \
> +	.channel = _channel, \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> +			      BIT(IIO_CHAN_INFO_AVERAGE_RAW) | \
> +			      BIT(IIO_CHAN_INFO_PROCESSED), \
> +	.datasheet_name = _name, \
> +	.indexed = 1. \
> +}
> +
> +static const struct iio_chan_spec rn5t618_adc_iio_channels[] = {
> +	RN5T618_ADC_CHANNEL(0, IIO_CURRENT, "LIMMON"),
> +	RN5T618_ADC_CHANNEL(1, IIO_VOLTAGE, "VBAT"),
> +	RN5T618_ADC_CHANNEL(2, IIO_VOLTAGE, "VADP"),
> +	RN5T618_ADC_CHANNEL(3, IIO_VOLTAGE, "VUSB"),
> +	RN5T618_ADC_CHANNEL(4, IIO_VOLTAGE, "VSYS"),
> +	RN5T618_ADC_CHANNEL(5, IIO_VOLTAGE, "VTHM"),
> +	RN5T618_ADC_CHANNEL(6, IIO_VOLTAGE, "AIN1"),
> +	RN5T618_ADC_CHANNEL(7, IIO_VOLTAGE, "AIN0")
> +};
> +
> +static int rn5t618_adc_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct iio_dev *iio_dev;
> +	struct rn5t618_adc_data *adc;
> +	struct rn5t618 *rn5t618 = dev_get_drvdata(pdev->dev.parent);
> +
> +	iio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
> +	if (!iio_dev) {
> +		dev_err(&pdev->dev, "failed allocating iio device\n");
> +		return -ENOMEM;
> +	}
> +
> +	adc = iio_priv(iio_dev);
> +	adc->dev = &pdev->dev;
> +	adc->rn5t618 = rn5t618;
> +	adc->irq = -ENOENT;
> +
> +	if (rn5t618->irq_data)
> +		adc->irq = regmap_irq_get_virq(rn5t618->irq_data,
> +					       RN5T618_IRQ_ADC);
> +
> +	if (adc->irq  < 0) {

Extra space before the <
For an irq 0 usually counts as 'no irq'.  Can that particular
path ever give that?

> +		dev_err(&pdev->dev, "get virq failed\n");
> +		return adc->irq;
> +	}
> +
> +	init_completion(&adc->conv_completion);
> +
> +	iio_dev->name = dev_name(&pdev->dev);
> +	iio_dev->dev.parent = &pdev->dev;
> +	iio_dev->info = &rn5t618_adc_iio_info;
> +	iio_dev->modes = INDIO_DIRECT_MODE;
> +	iio_dev->channels = rn5t618_adc_iio_channels;
> +	iio_dev->num_channels = ARRAY_SIZE(rn5t618_adc_iio_channels);
> +
> +	/* stop any auto-conversion */
> +	ret = regmap_write(rn5t618->regmap, RN5T618_ADCCNT3, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, iio_dev);
> +
> +	ret = request_threaded_irq(adc->irq, NULL,
> +				   rn5t618_adc_irq,
> +				   IRQF_ONESHOT, dev_name(adc->dev),
> +				   adc);
> +	if (ret < 0) {
> +		dev_err(adc->dev, "request irq %d failed: %d\n", adc->irq, ret);
> +		return ret;
> +	}
> +
> +	ret = iio_device_register(iio_dev);
> +	if (ret < 0)
> +		free_irq(adc->irq, adc);
> +
> +	return ret;
> +}
> +
> +static int rn5t618_adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *iio_dev = platform_get_drvdata(pdev);
> +	struct rn5t618_adc_data *adc = iio_priv(iio_dev);
> +
> +	iio_device_unregister(iio_dev);
> +	free_irq(adc->irq, adc);

If this is all we are going to have in remove, why not just use
the device managed form to do it for us and get rid of remove.

> +
> +	return 0;
> +}
> +
> +static struct platform_driver rn5t618_adc_driver = {
> +	.driver = {
> +		.name   = "rn5t618-adc",
> +	},
> +	.probe = rn5t618_adc_probe,
> +	.remove = rn5t618_adc_remove,
> +};
> +
> +module_platform_driver(rn5t618_adc_driver);
> +MODULE_ALIAS("platform:rn5t618-adc");
> +MODULE_DESCRIPTION("RICOH RN5T618 ADC driver");
> +MODULE_LICENSE("GPL");
> +