Re: [PATCH v1 2/2] iio: adc: add NPCM ADC driver

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 25 Dec 2018 23:00:11 +0100 (CET)
Peter Meerwald-Stadler <pmeerw@pmeerw.net> wrote:

> Hello,
> 
> > Add Nuvoton NPCM BMC Analog-to-Digital Converter(ADC) driver.  
> 
> some minor comments below...
+ a few more from me.

Generally looking pretty good.

Jonathan

>  
> > The NPCM ADC is a 10-bit converter for eight channel inputs.
> > 
> > Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
> > ---
> >  drivers/iio/adc/Kconfig    |  10 ++
> >  drivers/iio/adc/Makefile   |   1 +
> >  drivers/iio/adc/npcm_adc.c | 336 +++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 347 insertions(+)
> >  create mode 100644 drivers/iio/adc/npcm_adc.c
> > 
> > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> > index a52fea8749a9..63a4204c5673 100644
> > --- a/drivers/iio/adc/Kconfig
> > +++ b/drivers/iio/adc/Kconfig
> > @@ -555,6 +555,16 @@ config NAU7802
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called nau7802.
> >  
> > +config NPCM_ADC
> > +	tristate "Nuvoton NPCM ADC driver"
> > +	depends on ARCH_NPCM || COMPILE_TEST
> > +	depends on HAS_IOMEM
> > +	help
> > +	  Say yes here to build support for Nuvoton NPCM ADC.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called npcm_adc.
> > +
> >  config PALMAS_GPADC
> >  	tristate "TI Palmas General Purpose ADC"
> >  	depends on MFD_PALMAS
> > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> > index a6e6a0b659e2..b0c3f3b73a5f 100644
> > --- a/drivers/iio/adc/Makefile
> > +++ b/drivers/iio/adc/Makefile
> > @@ -53,6 +53,7 @@ obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
> >  obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
> >  obj-$(CONFIG_MXS_LRADC_ADC) += mxs-lradc-adc.o
> >  obj-$(CONFIG_NAU7802) += nau7802.o
> > +obj-$(CONFIG_NPCM_ADC) += npcm_adc.o
> >  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
> >  obj-$(CONFIG_QCOM_SPMI_ADC5) += qcom-spmi-adc5.o
> >  obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
> > diff --git a/drivers/iio/adc/npcm_adc.c b/drivers/iio/adc/npcm_adc.c
> > new file mode 100644
> > index 000000000000..4f7851472997
> > --- /dev/null
> > +++ b/drivers/iio/adc/npcm_adc.c
> > @@ -0,0 +1,336 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (c) 2016-2018 Nuvoton Technology corporation.

Slight preference for not using c++ comments except for the 
SPDX line.  This is mostly for consistency with older
code that predates this even being an accepted option!

> > +
> > +#include <linux/clk.h>
> > +#include <linux/device.h>
> > +#include <linux/mfd/syscon.h>
> > +#include <linux/io.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/regmap.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/spinlock.h>
> > +#include <linux/uaccess.h>
> > +
> > +struct npcm_adc {
> > +	u32 vref_mv;
> > +	bool int_status;
> > +	u32 adc_sample_hz;
> > +	struct device *dev;
> > +	void __iomem *regs;
> > +	struct clk *adc_clk;
> > +	wait_queue_head_t wq;
> > +	struct regulator *vref;
> > +	struct regmap *rst_regmap;
> > +};
> > +
> > +/* NPCM7xx reset module */
> > +#define IPSRST1_OFFSET		0x020  
> 
> NPCM_ prefix please
> 
> > +#define IPSRST1_ADC_RST		BIT(27)
> > +
> > +/* ADC registers */
> > +#define NPCM_ADCCON	 0x00
> > +#define NPCM_ADCDATA	 0x04
> > +
> > +/* ADCCON Register Bits */
> > +#define NPCM_ADCCON_ADC_INT_EN		BIT(21)
> > +#define NPCM_ADCCON_REFSEL		BIT(19)
> > +#define NPCM_ADCCON_ADC_INT_ST		BIT(18)
> > +#define NPCM_ADCCON_ADC_EN		BIT(17)
> > +#define NPCM_ADCCON_ADC_RST		BIT(16)
> > +#define NPCM_ADCCON_ADC_CONV		BIT(13)
> > +
> > +#define NPCM_ADCCON_CH_MASK		GENMASK(27, 24)
> > +#define NPCM_ADCCON_CH(x)		((x) << 24)
> > +#define NPCM_ADCCON_DIV_SHIFT		1
> > +#define NPCM_ADCCON_DIV_MASK		GENMASK(8, 1)
> > +#define NPCM_ADC_DATA_MASK(x)		((x) & GENMASK(9, 0))
> > +
> > +#define NPCM_ADC_ENABLE		(NPCM_ADCCON_ADC_EN | NPCM_ADCCON_ADC_INT_EN)
> > +
> > +/* ADC General Definition */
> > +#define NPCM_RESOLUTION_BITS		10
> > +#define ADC_DEFAULT_SAMPLE_RATE		12500000  
> 
> NPCM_ prefix please
> 
> > +#define INT_VREF_MV			2000
> > +
> > +#define NPCM_ADC_CHAN(ch) {					\
> > +	.type = IIO_VOLTAGE,					\
> > +	.indexed = 1,						\
> > +	.channel = ch,						\
> > +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> > +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\  
> 
> SAMPLE_FREQ might be missing, it is implemented in _read()
> 
> > +}
> > +
> > +static const struct iio_chan_spec npcm_adc_iio_channels[] = {
> > +	NPCM_ADC_CHAN(0),
> > +	NPCM_ADC_CHAN(1),
> > +	NPCM_ADC_CHAN(2),
> > +	NPCM_ADC_CHAN(3),
> > +	NPCM_ADC_CHAN(4),
> > +	NPCM_ADC_CHAN(5),
> > +	NPCM_ADC_CHAN(6),
> > +	NPCM_ADC_CHAN(7),
> > +};
> > +
> > +static irqreturn_t npcm_adc_isr(int irq, void *data)
> > +{
> > +	u32 regtemp = 0;  
> 
> initialization not needed
> 
> > +	struct iio_dev *indio_dev = data;
> > +	struct npcm_adc *info = iio_priv(indio_dev);
> > +
> > +	regtemp = ioread32(info->regs + NPCM_ADCCON);
> > +	if (regtemp & NPCM_ADCCON_ADC_INT_ST) {
> > +		iowrite32(regtemp, info->regs + NPCM_ADCCON);
> > +		wake_up_interruptible(&info->wq);
> > +		info->int_status = true;
> > +	}
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int npcm_adc_read(struct npcm_adc *info, int *val, u8 channel)
> > +{
> > +	int ret;
> > +	u32 regtemp = 0;  
> 
> initialization not needed
> > +
> > +	/* Select ADC channal */  
> 
> channel
> 
> > +	regtemp = ioread32(info->regs + NPCM_ADCCON);
> > +	regtemp &= ~NPCM_ADCCON_CH_MASK;
> > +	iowrite32(regtemp | NPCM_ADCCON_CH(channel) |
> > +		  NPCM_ADCCON_ADC_CONV, info->regs + NPCM_ADCCON);
> > +
> > +	info->int_status = false;  
> 
> this might be racy; shouldn't int_status be set to false before starting 
> the conversion
> 
> > +	ret = wait_event_interruptible_timeout(info->wq, info->int_status,
> > +					       msecs_to_jiffies(10));
> > +	if (ret == 0) {
> > +		regtemp = ioread32(info->regs + NPCM_ADCCON);
> > +		if ((regtemp & NPCM_ADCCON_ADC_CONV) && info->rst_regmap) {
> > +			/* if conversion failed - reset ADC module */
> > +			regmap_write(info->rst_regmap, IPSRST1_OFFSET,
> > +				     IPSRST1_ADC_RST);
> > +			msleep(100);
> > +			regmap_write(info->rst_regmap, IPSRST1_OFFSET, 0x0);
> > +			msleep(100);
> > +
> > +			/* Enable ADC and start conversion Module */  
> 
> module (lowercase)
> 
> > +			iowrite32(NPCM_ADC_ENABLE | NPCM_ADCCON_ADC_CONV,
> > +				  info->regs + NPCM_ADCCON);
> > +			dev_err(info->dev, "RESET ADC Complete\n");
> > +		}
> > +		return -ETIMEDOUT;
> > +	}
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*val = NPCM_ADC_DATA_MASK(ioread32(info->regs + NPCM_ADCDATA));
> > +
> > +	return 0;
> > +}
> > +
> > +static int npcm_adc_read_raw(struct iio_dev *indio_dev,
> > +			     struct iio_chan_spec const *chan, int *val,
> > +			     int *val2, long mask)
> > +{
> > +	int ret;
> > +	struct npcm_adc *info = iio_priv(indio_dev);
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		mutex_lock(&indio_dev->mlock);
> > +		ret = npcm_adc_read(info, val, chan->channel);
> > +		if (ret) {
> > +			dev_err(info->dev, "NPCM ADC read failed\n");
> > +			mutex_unlock(&indio_dev->mlock);

Unlock before checking ret.  Then only one unlock is needed for the
good and bad paths.

> > +			return ret;
> > +		}
> > +		mutex_unlock(&indio_dev->mlock);
> > +		return IIO_VAL_INT;
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*val = info->vref_mv;
> > +		*val2 = NPCM_RESOLUTION_BITS;
> > +		return IIO_VAL_FRACTIONAL_LOG2;
> > +	case IIO_CHAN_INFO_SAMP_FREQ:
> > +		*val = info->adc_sample_hz;
> > +		return IIO_VAL_INT;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct iio_info npcm_adc_iio_info = {
> > +	.read_raw = &npcm_adc_read_raw,
> > +};
> > +
> > +static const struct of_device_id npcm_adc_match[] = {
> > +	{ .compatible = "nuvoton,npcm750-adc", },
> > +	{ /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, npcm_adc_match);
> > +
> > +static int npcm_adc_probe(struct platform_device *pdev)
> > +{
> > +	int ret;
> > +	int irq;
> > +	u32 div;
> > +	u32 reg_con;
> > +	struct resource *res;
> > +	struct npcm_adc *info;
> > +	struct iio_dev *indio_dev;
> > +	struct device *dev = &pdev->dev;
> > +	struct device_node *np = pdev->dev.of_node;
> > +
> > +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*info));
> > +	if (!indio_dev)
> > +		return -ENOMEM;
> > +	info = iio_priv(indio_dev);
> > +
> > +	info->dev = &pdev->dev;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	info->regs = devm_ioremap_resource(&pdev->dev, res);
> > +	if (IS_ERR(info->regs))
> > +		return PTR_ERR(info->regs);
> > +
> > +	info->adc_clk = devm_clk_get(&pdev->dev, NULL);
> > +	if (IS_ERR(info->adc_clk)) {
> > +		dev_warn(&pdev->dev, "ADC clock failed: can't read clk, Assuming ADC clock Rate 12.5MHz\n");  
> 
> assuming, rate (lowercase)
> 
> > +		info->adc_sample_hz = ADC_DEFAULT_SAMPLE_RATE;
> > +	} else {
> > +		/* calculate ADC clock sample rate */
> > +		reg_con = ioread32(info->regs + NPCM_ADCCON);
> > +		div = reg_con & NPCM_ADCCON_DIV_MASK;
> > +		div = div >> NPCM_ADCCON_DIV_SHIFT;
> > +		info->adc_sample_hz = clk_get_rate(info->adc_clk) /
> > +			((div + 1) * 2);
> > +	}
> > +
> > +	if (of_device_is_compatible(np, "nuvoton,npcm750-adc")) {
> > +		info->rst_regmap = syscon_regmap_lookup_by_compatible
> > +			("nuvoton,npcm750-rst");
> > +		if (IS_ERR(info->rst_regmap)) {
> > +			dev_err(&pdev->dev, "Failed to find nuvoton,npcm750-rst\n");
> > +			ret = PTR_ERR(info->rst_regmap);
> > +			goto err_disable_clk;
> > +		}
> > +	}
> > +
> > +	reg_con = ioread32(info->regs + NPCM_ADCCON);
> > +	info->vref = devm_regulator_get_optional(&pdev->dev, "vref");
> > +	if (!IS_ERR(info->vref)) {
> > +		ret = regulator_enable(info->vref);
> > +		if (ret) {
> > +			dev_err(&pdev->dev, "Can't enable ADC reference voltage\n");
> > +			goto err_disable_clk;
> > +		}
> > +
> > +		ret = regulator_get_voltage(info->vref);
> > +		if (ret < 0)
> > +			goto err_disable_vref_reg;

As reading voltage is normally only done for the scale attribute and that
should never be in a fast path, I generally think it is better to read
the reference voltage when needed.  It might have changed...

> > +
> > +		info->vref_mv = ret / 1000;
> > +		iowrite32(reg_con & ~NPCM_ADCCON_REFSEL,
> > +			  info->regs + NPCM_ADCCON);
> > +	} else {
> > +		/* Any other error indicates that the regulator does exist */  
> 
> does not?
I think it is correct as it stands, but could be worded clearer.
Perhaps "Any error which is not ENODEV indicates the regulator has been specified and so is a failure case".
> 
> > +		if (PTR_ERR(info->vref) != -ENODEV) {
> > +			goto err_disable_clk;
> > +			return PTR_ERR(info->vref);
> > +		}
> > +
> > +		/* Use internal reference */
> > +		info->vref_mv = INT_VREF_MV;
> > +		iowrite32(reg_con | NPCM_ADCCON_REFSEL,
> > +			  info->regs + NPCM_ADCCON);
> > +	}
> > +
> > +	irq = platform_get_irq(pdev, 0);
> > +	if (irq <= 0) {
> > +		dev_err(dev, "failed getting interrupt resource\n");
> > +		ret = -EINVAL;
> > +		goto err_disable_vref_reg;
> > +	}
> > +
> > +	ret = devm_request_irq(&pdev->dev, irq, npcm_adc_isr, 0,
> > +			       "NPCM_ADC", indio_dev);
> > +	if (ret < 0) {
> > +		dev_err(dev, "failed requesting interrupt\n");
> > +		goto err_disable_vref_reg;
> > +	}
> > +
> > +	init_waitqueue_head(&info->wq);
> > +
> > +	platform_set_drvdata(pdev, indio_dev);
> > +	indio_dev->name = dev_name(&pdev->dev);
> > +	indio_dev->dev.parent = &pdev->dev;
> > +	indio_dev->info = &npcm_adc_iio_info;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = npcm_adc_iio_channels;
> > +	indio_dev->num_channels = ARRAY_SIZE(npcm_adc_iio_channels);
> > +
> > +	ret = iio_device_register(indio_dev);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "Couldn't register the device.\n");
> > +		goto err_disable_vref_reg;
> > +	}
> > +  
> 
> might be racy; I'd rather do this before _register()
> the device could be in a half-initialized state
> 
> > +	reg_con = ioread32(info->regs + NPCM_ADCCON);
> > +	reg_con |= NPCM_ADC_ENABLE;
> > +
> > +	/* Enable the ADC Module */  
> 
> module (lowercase)
> 
> > +	iowrite32(reg_con, info->regs + NPCM_ADCCON);
> > +
> > +	/* Start ADC conversion */
> > +	iowrite32(reg_con | NPCM_ADCCON_ADC_CONV, info->regs + NPCM_ADCCON);
> > +
> > +	pr_info("NPCM ADC driver probed, sample Rate %dHz\n",
> > +		info->adc_sample_hz);  
> 
> don't do this logging, it just clutters the log
> 
> > +
> > +	return 0;
> > +
> > +err_disable_vref_reg:
> > +	if (!IS_ERR(info->vref))
> > +		regulator_disable(info->vref);
> > +err_disable_clk:
> > +	clk_disable_unprepare(info->adc_clk);
> > +
> > +	return ret;
> > +}
> > +
> > +static int npcm_adc_remove(struct platform_device *pdev)
> > +{
> > +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> > +	struct npcm_adc *info = iio_priv(indio_dev);
> > +	u32 regtemp = 0;  
> 
> no initialization needed
> 
> > +
> > +	regtemp = ioread32(info->regs + NPCM_ADCCON);
> > +
> > +	/* Disable the ADC Module */
> > +	iowrite32(regtemp & ~NPCM_ADCCON_ADC_EN, info->regs + NPCM_ADCCON);
> > +
> > +	iio_device_unregister(indio_dev);
> > +	clk_disable_unprepare(info->adc_clk);
> > +	if (!IS_ERR(info->vref))
> > +		regulator_disable(info->vref);
> > +
> > +	return 0;
> > +}
> > +
> > +static struct platform_driver npcm_adc_driver = {
> > +	.probe		= npcm_adc_probe,
> > +	.remove		= npcm_adc_remove,
> > +	.driver		= {
> > +		.name	= "npcm_adc",
> > +		.of_match_table = npcm_adc_match,
> > +	},
> > +};
> > +
> > +module_platform_driver(npcm_adc_driver);
> > +
> > +MODULE_DESCRIPTION("Nuvoton NPCM ADC Sensor Driver");  
> 
> I'd rather drop 'sensor'
> 
> > +MODULE_AUTHOR("Tomer Maimon <tomer.maimon@nuvoton.com>");
> > +MODULE_LICENSE("GPL v2");
> >   
>