Subject: [PATCH v2 1/5] iio:adc:at91_adc8xx: introduce new atmel adc driver

From: [email-masked] (Jonathan Cameron)
Date: Sun, 10 Jan 2016 11:28:00 +0000

On 06/01/16 16:12, Ludovic Desroches wrote:
> This driver supports the new version of the Atmel ADC device introduced
> with the SAMA5D2 SoC family.
> 
> Signed-off-by: Ludovic Desroches <[email-masked]>
Hi Ludovic,

A couple of bits and bobs inline + I'd ideally like a device tree ack
(or as conventions says I'll have to wait a while before ignoring them ;)

The new sampling_frequency attr should be done through info_mask_shared_by_all.

Also, you are effectively claiming to have handled a set of interrupts that
you weren't expecting.  Convention would be to say 'not me!' if that happens
rather than IRQ handled.  Obviously they won't currently happen unless
something odd is going on, but best to get it 'obviously' right!

On the whether to read in or our of the interrupt handler, I'm happy with it
being where it is for the reasons you stated in the previous thread.
I'd gotten myself confused on this so lets pretend I never mentioned it.
Just possible we'll later want to move to a threaded interrupt as you add
more functionality to the handler (thresholds etc) but that can be revisited
when it matters.

Looking good in general though.  There are some features in this part
that I hope you get time to look at adding in future. I'm just
noting them down here for my own records as I've been reading the datasheet.

Easy stuff:
* differential inputs.
* gain and offset corrections
* sequencer (leading to wanting to use the buffered IIO side of things)
  The interaction of available channel count vs sequence length is unusual
  but won't effect standard sample everything once usage..

More 'interesting'
* in and out of window events.
* lots of triggers including different triggering for the last channel
 (interesting)
* DMA. Looks like a sensible setup so will be interesting to see how
  this fits in with the new DMA buffer support in IIO (at first glance
  I think it will drop straight in but I could be wrong).

Stuff I don't care about ;) (never have screens on the boards I use)
* touchscreen - one day we'll figure out if the way these are done
are generic enough to share infrastructure across different parts...

Very sensible to do a basic driver first though and build from there.

Thanks,

Jonathan

> ---
>  .../devicetree/bindings/iio/adc/at91_adc8xx.txt    |  28 ++
>  drivers/iio/adc/Kconfig                            |  11 +
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/at91_adc8xx.c                      | 461 +++++++++++++++++++++
>  4 files changed, 501 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/at91_adc8xx.txt
>  create mode 100644 drivers/iio/adc/at91_adc8xx.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/at91_adc8xx.txt b/Documentation/devicetree/bindings/iio/adc/at91_adc8xx.txt
> new file mode 100644
> index 0000000..14fe441
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/at91_adc8xx.txt
> @@ -0,0 +1,28 @@
> +* AT91 SAMA5D2 Analog to Digital Converter (ADC)
> +
> +Required properties:
> +  - compatible: Should be "atmel,sama5d2-adc".
> +  - reg: Should contain ADC registers location and length.
> +  - interrupts: Should contain the IRQ line for the ADC.
> +  - clocks: phandle to device clock.
> +  - clock-names: Must be "adc_clk".
> +  - vref-supply: Supply used as reference for conversions.
> +  - vddana-supply: Supply for the adc device.
> +  - atmel,min-sample-rate: Minimum sampling rate, it depends on SoC.
> +  - atmel,max-sample-rate: Maximum sampling rate, it depends on SoC.
Hmm. Just a thought - should we have units for the sample-rate ones as
well?  It's kind of obvious they are in Hz but maybe we want it anyway
for consistency...

Otherwise the bindings look fine to me.  I always appreciate
a quick look from a device tree maintainer though as I've been
wrong many times before!

> +  - atmel,startup-time-ms: Startup time expressed in ms, it depends on SoC.
> +
> +Example:
> +
> +adc: adc at fc030000 {
> +	compatible = "atmel,sama5d2-adc";
> +	reg = <0xfc030000 0x100>;
> +	interrupts = <40 IRQ_TYPE_LEVEL_HIGH 7>;
> +	clocks = <&adc_clk>;
> +	clock-names = "adc_clk";
> +	atmel,min-sample-rate = <200000>;
> +	atmel,max-sample-rate = <20000000>;
> +	atmel,startup-time-ms = <4>;
> +	vddana-supply = <&vdd_3v3_lp_reg>;
> +	vref-supply = <&vdd_3v3_lp_reg>;
> +}
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 605ff42..ee45468 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -131,6 +131,17 @@ config AT91_ADC
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called at91_adc.
>  
> +config AT91_ADC8xx
> +	tristate "Atmel AT91 ADC 8xx"
> +	depends on ARCH_AT91
> +	depends on INPUT
> +	help
> +	  Say yes here to build support for Atmel ADC 8xx which is available
> +	  from SAMA5D2 SoC family.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called at91_adc8xx.
> +
>  config AXP288_ADC
>  	tristate "X-Powers AXP288 ADC driver"
>  	depends on MFD_AXP20X
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 6435780..c0d5d02 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_AD7793) += ad7793.o
>  obj-$(CONFIG_AD7887) += ad7887.o
>  obj-$(CONFIG_AD799X) += ad799x.o
>  obj-$(CONFIG_AT91_ADC) += at91_adc.o
> +obj-$(CONFIG_AT91_ADC8xx) += at91_adc8xx.o
Hohum.  There's a fairly strong hint here that we might be using names
that are too generic for atmel parts ;)

Strange question, where does the 8xx naming come from?
I wonder if we are better off taking the convention we tend
to use for discrete parts and naming it after the first one
supported.  So this would be
at91_sama5d2_adc then listing parts we know are supported in the
Kconfig help.

>  obj-$(CONFIG_AXP288_ADC) += axp288_adc.o
>  obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
>  obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
> diff --git a/drivers/iio/adc/at91_adc8xx.c b/drivers/iio/adc/at91_adc8xx.c
> new file mode 100644
> index 0000000..bed9574
> --- /dev/null
> +++ b/drivers/iio/adc/at91_adc8xx.c
> @@ -0,0 +1,461 @@
> +/*
> + * Atmel ADC driver for SAMA5D2 devices and later.
You are an optimist if you think it won't change in the future.
Lets be cynical and say 'and compatible'. 
> + *
> + * Copyright (C) 2015 Atmel,
> + *               2015 Ludovic Desroches <[email-masked]>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/sched.h>
> +#include <linux/wait.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/regulator/consumer.h>
> +
Rather than being tight on space for the coments, my personal preference
is
/* comment */
#define FOO

That way there is lots of room to add as much documentation as makes
sense rather than thinking - wow this line is too long, better cut some
of it out!

> +#define AT91_ADC8XX_CR		0x00			/* Control Register */
> +#define		AT91_ADC8XX_CR_SWRST		BIT(0)		/* Software Reset */
> +#define		AT91_ADC8XX_CR_START		BIT(1)		/* Start Conversion */
> +#define		AT91_ADC8XX_CR_TSCALIB		BIT(2)		/* Touchscreen Calibration */
> +#define		AT91_ADC8XX_CR_CMPRST		BIT(4)		/* Comparison Restart */
> +#define AT91_ADC8XX_MR		0x04			/* Mode Register */
> +#define		AT91_ADC8XX_MR_TRGSEL(v)	((v) << 1)	/* Trigger Selection */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG0	0		/* ADTRG */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG1	1		/* TIOA0 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG2	2		/* TIOA1 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG3	3		/* TIOA2 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG4	4		/* PWM event line 0 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG5	5		/* PWM event line 1 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG6	6		/* TIOA3 */
> +#define			AT91_ADC8XX_MR_TRGSEL_TRIG7	7		/* RTCOUT0 */
> +#define		AT91_ADC8XX_MR_SLEEP		BIT(5)		/* Sleep Mode */
> +#define		AT91_ADC8XX_MR_FWUP		BIT(6)		/* Fast Wake Up */
> +#define		AT91_ADC8XX_MR_PRESCAL(v)	((v) << AT91_ADC8XX_MR_PRESCAL_OFFSET)	/* Prescaler Rate Selection */
> +#define			AT91_ADC8XX_MR_PRESCAL_OFFSET	8
> +#define			AT91_ADC8XX_MR_PRESCAL_MAX	0xff
> +#define		AT91_ADC8XX_MR_STARTUP(v)	((v) << 16)	/* Startup Time */
> +#define		AT91_ADC8XX_MR_ANACH		BIT(23)		/* Analog Change */
> +#define		AT91_ADC8XX_MR_TRACKTIM(v)	((v) << 24)	/* Tracking Time */
> +#define			AT91_ADC8XX_MR_TRACKTIM_MAX	0xff
> +#define		AT91_ADC8XX_MR_TRANSFER(v)	((v) << 28)	/* Transfer Time */
> +#define			AT91_ADC8XX_MR_TRANSFER_MAX	0x3
> +#define		AT91_ADC8XX_MR_USEQ		BIT(31)		/* Use Sequence Enable */
> +#define AT91_ADC8XX_SEQR1	0x08			/* Channel Sequence Register 1 */
> +#define AT91_ADC8XX_SEQR2	0x0c			/* Channel Sequence Register 2 */
> +#define AT91_ADC8XX_CHER	0x10			/* Channel Enable Register */
> +#define AT91_ADC8XX_CHDR	0x14			/* Channel Disable Register */
> +#define AT91_ADC8XX_CHSR	0x18			/* Channel Status Register */
> +#define AT91_ADC8XX_LCDR	0x20			/* Last Converted Data Register */
> +#define AT91_ADC8XX_IER		0x24			/* Interrupt Enable Register */
> +#define AT91_ADC8XX_IDR		0x28			/* Interrupt Disable Register */
> +#define AT91_ADC8XX_IMR		0x2c			/* Interrupt Mask Register */
> +#define AT91_ADC8XX_ISR		0x30			/* Interrupt Status Register */
> +#define AT91_ADC8XX_LCTMR	0x34			/* Last Channel Trigger Mode Register */
> +#define AT91_ADC8XX_LCCWR	0x38			/* Last Channel Compare Window Register */
> +#define AT91_ADC8XX_OVER	0x3c			/* Overrun Status Register */
> +#define AT91_ADC8XX_EMR		0x40			/* Extended Mode Register */
> +#define AT91_ADC8XX_CWR		0x44			/* Compare Window Register */
> +#define AT91_ADC8XX_CGR		0x48			/* Channel Gain Register */
> +#define AT91_ADC8XX_COR		0x4c			/* Channel Offset Register */
> +#define AT91_ADC8XX_CDR0	0x50			/* Channel Data Register 0 */
> +#define AT91_ADC8XX_ACR		0x94			/* Analog Control Register */
> +#define AT91_ADC8XX_TSMR	0xb0			/* Touchscreen Mode Register */
> +#define AT91_ADC8XX_XPOSR	0xb4			/* Touchscreen X Position Register */
> +#define AT91_ADC8XX_YPOSR	0xb8			/* Touchscreen Y Position Register */
> +#define AT91_ADC8XX_PRESSR	0xbc			/* Touchscreen Pressure Register */
> +#define AT91_ADC8XX_TRGR	0xc0			/* Trigger Register */
> +#define AT91_ADC8XX_COSR	0xd0			/* Correction Select Register */
> +#define AT91_ADC8XX_CVR		0xd4			/* Correction Value Register */
> +#define AT91_ADC8XX_CECR	0xd8			/* Channel Error Correction Register */
> +#define AT91_ADC8XX_WPMR	0xe4			/* Write Protection Mode Register */
> +#define AT91_ADC8XX_WPSR	0xe8			/* Write Protection Status Register */
> +#define AT91_ADC8XX_VERSION	0xfc			/* Version Register */
> +
> +#define AT91_AT91_ADC8XX_CHAN(num, addr)				\
> +	{								\
> +		.type = IIO_VOLTAGE,					\
> +		.channel = num,						\
> +		.address = addr,					\
> +		.scan_type = {						\
> +			.sign = 'u',					\
> +			.realbits = 12,					\
> +		},							\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
as noted below you also want
.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
though under the ABI that could also be shared by type if you prefer.

> +		.datasheet_name = "CH"#num,				\
> +		.indexed = 1,						\
> +	}
> +
> +#define at91_adc_readl(st, reg)		readl_relaxed(st->base + reg)
> +#define at91_adc_writel(st, reg, val)	writel_relaxed(val, st->base + reg)
> +
> +struct at91_adc_soc_info {
> +	unsigned			startup_time;
> +	unsigned			min_sample_rate;
> +	unsigned			max_sample_rate;
> +};
> +
> +struct at91_adc_state {
> +	void __iomem			*base;
> +	int				irq;
> +	struct clk			*per_clk;
> +	struct regulator		*reg;
> +	struct regulator		*vref;
> +	u32				vref_uv;
> +	const struct iio_chan_spec	*chan;
> +	bool				conversion_done;
> +	u32				conversion_value;
> +	struct at91_adc_soc_info	soc_info;
> +	wait_queue_head_t		wq_data_available;
> +	struct mutex			lock;
> +};
> +
> +static const struct iio_chan_spec at91_adc_channels[] = {
> +	AT91_AT91_ADC8XX_CHAN(0, 0x50),
> +	AT91_AT91_ADC8XX_CHAN(1, 0x54),
> +	AT91_AT91_ADC8XX_CHAN(2, 0x58),
> +	AT91_AT91_ADC8XX_CHAN(3, 0x5c),
> +	AT91_AT91_ADC8XX_CHAN(4, 0x60),
> +	AT91_AT91_ADC8XX_CHAN(5, 0x64),
> +	AT91_AT91_ADC8XX_CHAN(6, 0x68),
> +	AT91_AT91_ADC8XX_CHAN(7, 0x6c),
> +	AT91_AT91_ADC8XX_CHAN(8, 0x70),
> +	AT91_AT91_ADC8XX_CHAN(9, 0x74),
> +	AT91_AT91_ADC8XX_CHAN(10, 0x78),
> +	AT91_AT91_ADC8XX_CHAN(11, 0x7c),
> +};
> +
> +static unsigned at91_adc_startup_time(unsigned startup_time_min,
> +				      unsigned adc_clk_khz)
> +{
> +	const unsigned startup_lookup[] = {
> +		  0,   8,  16,  24,
> +		 64,  80,  96, 112,
> +		512, 576, 640, 704,
> +		768, 832, 896, 960
> +		};
> +	unsigned ticks_min, i;
> +
> +	/*
> +	 * Since the adc frequency is checked before, there is no reason
> +	 * to not meet the startup time constraint.
> +	 */
> +
> +	ticks_min = startup_time_min * adc_clk_khz / 1000;
> +	for (i = 0; i < ARRAY_SIZE(startup_lookup); i++)
> +		if (startup_lookup[i] > ticks_min)
> +			break;
> +
> +	return i;
> +}
> +
> +static void at91_adc_setup_samp_freq(struct at91_adc_state *st, unsigned freq)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(st);
> +	unsigned f_per, prescal, startup;
> +
> +	f_per = clk_get_rate(st->per_clk);
> +	prescal = (f_per / (2 * freq)) - 1;
> +
> +	startup = at91_adc_startup_time(st->soc_info.startup_time,
> +					freq / 1000);
> +
> +	at91_adc_writel(st, AT91_ADC8XX_MR,
> +			AT91_ADC8XX_MR_TRANSFER(2)
> +			| AT91_ADC8XX_MR_STARTUP(startup)
> +			| AT91_ADC8XX_MR_PRESCAL(prescal));
> +
> +	dev_dbg(&indio_dev->dev, "freq: %u, startup: %u, prescal: %u\n",
> +		freq, startup, prescal);
> +}
> +
> +static ssize_t at91_adc_show_samp_freq(struct device *dev,
> +				       struct device_attribute *attr,
> +				       char *buf)
> +{
> +	struct at91_adc_state *st = iio_priv(dev_to_iio_dev(dev));
> +	unsigned f_adc, f_per = clk_get_rate(st->per_clk);
> +	unsigned mr, prescal;
> +
> +	mr = at91_adc_readl(st, AT91_ADC8XX_MR);
> +	prescal = (mr >> AT91_ADC8XX_MR_PRESCAL_OFFSET)
> +		  & AT91_ADC8XX_MR_PRESCAL_MAX;
> +	f_adc = f_per / (2 * (prescal + 1));
> +
> +	return sprintf(buf, "%d\n", f_adc);
> +}
> +
> +static ssize_t at91_adc_store_samp_freq(struct device *dev,
> +					struct device_attribute *attr,
> +					const char *buf, size_t len)
> +{
> +	struct at91_adc_state *st = iio_priv(dev_to_iio_dev(dev));
> +	unsigned val;
> +	int ret;
> +
> +	ret = kstrtouint(buf, 10, &val);
> +	if (ret)
> +		return -EINVAL;
> +
> +	if (val < st->soc_info.min_sample_rate ||
> +	    val > st->soc_info.max_sample_rate)
> +		return -EINVAL;
> +
> +	at91_adc_setup_samp_freq(st, val);
> +
> +	return len;
> +}
> +
> +static IIO_DEV_ATTR_SAMP_FREQ(S_IRUGO | S_IWUSR,
> +			      at91_adc_show_samp_freq,
> +			      at91_adc_store_samp_freq);
> +
> +static struct attribute *at91_adc_event_attributes[] = {
> +	&iio_dev_attr_sampling_frequency.dev_attr.attr,
Use the info_mask_shared_by_all bitmap to specify this and
read it through read_raw.  That makes the funcationality available
to in kernel client drivers as well as userspace.

> +	NULL,
> +};
> +
> +static struct attribute_group at91_adc_event_attribute_group = {
> +	.attrs = at91_adc_event_attributes,
> +};
> +
> +static irqreturn_t at91_adc_interrupt(int irq, void *private)
> +{
> +	struct iio_dev *indio = private;
> +	struct at91_adc_state *st = iio_priv(indio);
> +	u32 status = at91_adc_readl(st, AT91_ADC8XX_ISR);
> +
> +	status &= at91_adc_readl(st, AT91_ADC8XX_IMR);

This is somewhat of an oddity.  If the interrupt is not enabled and we
get it then we have a nasty problem and so shouldn't claim to have
handled the interrupt (let the interrupt storm prevention stuff kill the
interrupt off this happens).

You should only be checking for those interrupts that this driver might
have caused - handling those and returning IRQ_NONE if you haven't caused
them to occur.

In this case you are enabling one of bits 0-11 that I can see so should
only be handling those.

> +	if (status & 0xffff) {
> +		st->conversion_value = at91_adc_readl(st, st->chan->address);
I'm happy enough with your logic here on reading this in the interrupt routine.
> +		st->conversion_done = true;
> +		wake_up_interruptible(&st->wq_data_available);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int at91_adc_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	struct at91_adc_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&st->lock);
> +
> +		st->chan = chan;
> +
> +		at91_adc_writel(st, AT91_ADC8XX_CHER, BIT(chan->channel));
> +		at91_adc_writel(st, AT91_ADC8XX_IER, BIT(chan->channel));
> +		at91_adc_writel(st, AT91_ADC8XX_CR, AT91_ADC8XX_CR_START);
> +
> +		ret = wait_event_interruptible_timeout(st->wq_data_available,
> +						       st->conversion_done,
> +						       msecs_to_jiffies(1000));
> +		if (ret == 0)
> +			ret = -ETIMEDOUT;
> +
> +		if (ret > 0) {
> +			*val = st->conversion_value;
> +			ret = IIO_VAL_INT;
> +			st->conversion_done = false;
> +		}
> +
> +		at91_adc_writel(st, AT91_ADC8XX_IDR, BIT(chan->channel));
> +		at91_adc_writel(st, AT91_ADC8XX_CHDR, BIT(chan->channel));
> +
> +		mutex_unlock(&st->lock);
> +		return ret;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_uv / 1000;
> +		*val2 = chan->scan_type.realbits;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info at91_adc_info = {
> +	.read_raw = &at91_adc_read_raw,
> +	.driver_module = THIS_MODULE,
> +	.event_attrs = &at91_adc_event_attribute_group,
> +};
> +
> +static int at91_adc_probe(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev;
> +	struct at91_adc_state *st;
> +	struct resource	*res;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev,
> +					  sizeof(struct at91_adc_state));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->name = dev_name(&pdev->dev);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &at91_adc_info;
> +	indio_dev->channels = at91_adc_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(at91_adc_channels);
> +
> +	st = iio_priv(indio_dev);
> +
> +	ret = of_property_read_u32(pdev->dev.of_node, "atmel,min-sample-rate",
> +				   &st->soc_info.min_sample_rate);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"invalid or missing value for atmel,min-sample-rate\n");
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u32(pdev->dev.of_node, "atmel,max-sample-rate",
> +				   &st->soc_info.max_sample_rate);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"invalid or missing value for atmel,max-sample-rate\n");
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u32(pdev->dev.of_node, "atmel,startup-time-ms",
> +				   &st->soc_info.startup_time);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"invalid or missing value for atmel,startup-time-ms\n");
> +		return ret;
> +	}
> +
> +	init_waitqueue_head(&st->wq_data_available);
> +	mutex_init(&st->lock);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -EINVAL;
> +
> +	st->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(st->base))
> +		return PTR_ERR(st->base);
> +
> +	st->irq = platform_get_irq(pdev, 0);
> +	if (st->irq <= 0) {
> +		if (!st->irq)
> +			st->irq = -ENXIO;
> +
> +		return st->irq;
> +	}
> +
> +	st->per_clk = devm_clk_get(&pdev->dev, "adc_clk");
> +	if (IS_ERR(st->per_clk))
> +		return PTR_ERR(st->per_clk);
> +
> +	st->reg = devm_regulator_get(&pdev->dev, "vddana");
> +	if (IS_ERR(st->reg))
> +		return PTR_ERR(st->reg);
> +
> +	st->vref = devm_regulator_get(&pdev->dev, "vref");
> +	if (IS_ERR(st->vref))
> +		return PTR_ERR(st->vref);
> +
> +	ret = devm_request_irq(&pdev->dev, st->irq, at91_adc_interrupt, 0,
> +			       pdev->dev.driver->name, indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	ret = regulator_enable(st->reg);
> +	if (ret)
> +		return ret;
> +
> +	ret = regulator_enable(st->vref);
> +	if (ret)
> +		goto reg_disable;
> +
> +	st->vref_uv = regulator_get_voltage(st->vref);
> +	if (st->vref_uv <= 0) {
> +		ret = -EINVAL;
> +		goto vref_disable;
> +	}
> +
> +	at91_adc_writel(st, AT91_ADC8XX_CR, AT91_ADC8XX_CR_SWRST);
> +	at91_adc_writel(st, AT91_ADC8XX_IDR, 0xffffffff);
> +
> +	at91_adc_setup_samp_freq(st, st->soc_info.min_sample_rate);
> +
> +	ret = clk_prepare_enable(st->per_clk);
> +	if (ret)
> +		goto vref_disable;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0)
> +		goto per_clk_disable_unprepare;
> +
> +	dev_info(&pdev->dev, "version: %x\n",
> +		 readl_relaxed(st->base + AT91_ADC8XX_VERSION));
> +
> +	return 0;
> +
> +per_clk_disable_unprepare:
> +	clk_disable_unprepare(st->per_clk);
> +vref_disable:
> +	regulator_disable(st->vref);
> +reg_disable:
> +	regulator_disable(st->reg);
> +	return ret;
> +}
> +
> +static int at91_adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +	struct at91_adc_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	clk_disable_unprepare(st->per_clk);
> +
> +	regulator_disable(st->vref);
> +	regulator_disable(st->reg);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id at91_adc_dt_match[] = {
> +	{
> +		.compatible = "atmel,sama5d2-adc",
> +	}, {
> +		/* sentinel */
> +	}
> +};
> +MODULE_DEVICE_TABLE(of, at91_adc_dt_match);
> +
> +static struct platform_driver at91_adc_driver = {
> +	.probe = at91_adc_probe,
> +	.remove = at91_adc_remove,
> +	.driver = {
> +		.name = "at91_adc8xx",
> +		.of_match_table = at91_adc_dt_match,
> +	},
> +};
> +module_platform_driver(at91_adc_driver)
> +
> +MODULE_AUTHOR("Ludovic Desroches <[email-masked]>");
> +MODULE_DESCRIPTION("Atmel AT91 ADC 8xx");
> +MODULE_LICENSE("GPL v2");
>