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Date:   Sun, 2 Feb 2020 17:33:55 +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, martin.blumenstingl@googlemail.com
Subject: Re: [PATCH v2 1/3] iio: adc: rn5t618: Add ADC driver for
 RN5T618/RC5T619
Message-ID: <20200202173355.1b949a37@archlinux>
In-Reply-To: <20200120212056.28806-2-andreas@kemnade.info>
References: <20200120212056.28806-1-andreas@kemnade.info>
        <20200120212056.28806-2-andreas@kemnade.info>
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On Mon, 20 Jan 2020 22:20:54 +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>
Sorry I missed one bigger thing in here around PROCESSED vs RAW.
See inline.

Thanks,

Jonathan

> ---
> Changes in v2:
> - enum for channels
> - bulk read instead of single byte read for conversion
>   result
> - fix get_virq error handling
> - use devm for registering device and requesting IRQ
> 
>  drivers/iio/adc/Kconfig       |  10 ++
>  drivers/iio/adc/Makefile      |   1 +
>  drivers/iio/adc/rn5t618-adc.c | 253 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 264 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:
Why :?
> +
> +	  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..667bd814569d
> --- /dev/null
> +++ b/drivers/iio/adc/rn5t618-adc.c
> @@ -0,0 +1,253 @@
> +// 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>
I may be missing something, but I'm not immediately seeing any irq_domain*
calls?  I suspect the only call is via stuff buried in regmap so we probably
don't need the header here.

> +
> +#define RN5T618_ADC_CONVERSION_TIMEOUT   (msecs_to_jiffies(500))
> +#define REFERENCE_VOLT 2500

Please prefix these defines
RN5T618_* 

It avoids potential clashes in future with things defined in headers.

> +
> +/* 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;
> +};
> +
> +enum rn5t618_channels {
> +	LIMMON = 0,
> +	VBAT,
> +	VADP,
> +	VUSB,
> +	VSYS,
> +	VTHM,
> +	AIN1,
> +	AIN0
> +};
> +
> +static const struct rn5t618_channel_ratios rn5t618_ratios[8] = {
> +	[LIMMON] = {50, 32}, /* measured across 20mOhm, amplified by 32 */
> +	[VBAT] = {2, 1},
> +	[VADP] = {3, 1},
> +	[VUSB] = {3, 1},
> +	[VSYS] = {3, 1},
> +	[VTHM] = {1, 1},
> +	[AIN1] = {1, 1},
> +	[AIN0] = {1, 1},
> +};
> +
> +static int rn5t618_read_adc_reg(struct rn5t618 *rn5t618, int reg, u16 *val)
> +{
> +	u8 data[2];
> +	int ret;
> +
> +	ret = regmap_bulk_read(rn5t618->regmap, reg, data, sizeof(data));
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = (data[0] << 4) | (data[1] & 0xF);
> +
> +	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;

This info should be provided as scale so that userspace can do the maths if
it wants to rather than handling it in kernel.

> +
> +	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), \

Sorry, I missed this before. 

As a general rule it makes no sense to expose both RAW and PROCESSED values.
It should be possible to work one out from the other if the relationship is
linear and scale is provided.

> +	.datasheet_name = _name, \
> +	.indexed = 1. \
> +}
> +
> +static const struct iio_chan_spec rn5t618_adc_iio_channels[] = {
> +	RN5T618_ADC_CHANNEL(LIMMON, IIO_CURRENT, "LIMMON"),
> +	RN5T618_ADC_CHANNEL(VBAT, IIO_VOLTAGE, "VBAT"),
> +	RN5T618_ADC_CHANNEL(VADP, IIO_VOLTAGE, "VADP"),
> +	RN5T618_ADC_CHANNEL(VUSB, IIO_VOLTAGE, "VUSB"),
> +	RN5T618_ADC_CHANNEL(VSYS, IIO_VOLTAGE, "VSYS"),
> +	RN5T618_ADC_CHANNEL(VTHM, IIO_VOLTAGE, "VTHM"),
> +	RN5T618_ADC_CHANNEL(AIN1, IIO_VOLTAGE, "AIN1"),
> +	RN5T618_ADC_CHANNEL(AIN0, 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;
> +
> +	if (rn5t618->irq_data)
> +		adc->irq = regmap_irq_get_virq(rn5t618->irq_data,
> +					       RN5T618_IRQ_ADC);
> +
> +	if (adc->irq <= 0) {
> +		dev_err(&pdev->dev, "get virq failed\n");
> +		return -EINVAL;
> +	}
> +
> +	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 = devm_request_threaded_irq(adc->dev, 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 = devm_iio_device_register(adc->dev, iio_dev);
> +
> +	return ret;
> +}
> +
> +static struct platform_driver rn5t618_adc_driver = {
> +	.driver = {
> +		.name   = "rn5t618-adc",
> +	},
> +	.probe = rn5t618_adc_probe,
> +};
> +
> +module_platform_driver(rn5t618_adc_driver);
> +MODULE_ALIAS("platform:rn5t618-adc");
> +MODULE_DESCRIPTION("RICOH RN5T618 ADC driver");
> +MODULE_LICENSE("GPL");