Re: [PATCH 2/9] ARM: AT91: IIO: Add AT91 ADC driver.

[Jonathan Cameron <jic23@cam.ac.uk>]

On 5/9/2012 2:02 PM, Maxime Ripard wrote:
> Add the ADC driver for Atmel's AT91SAM9G20-EK, AT91SAM9M10G45-EK
> and AT91SAM9X5 family boards.
>
> It has support for both software and hardware triggers.
Totally trivial, but please add a newline where it says below. 
Otherwise, looks
fine to me.  Couple of other passing comments inline, but nothing else 
to change
unless you particularly want to.
> Signed-off-by: Maxime Ripard<maxime.ripard@free-electrons.com>
> Acked-by: Nicolas Ferre<nicolas.ferre@atmel.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
> ---
>   drivers/iio/Kconfig        |    2 +
>   drivers/iio/Makefile       |    2 +
>   drivers/iio/adc/Kconfig    |   16 ++
>   drivers/iio/adc/Makefile   |    5 +
>   drivers/iio/adc/at91_adc.c |  673 ++++++++++++++++++++++++++++++++++++++++++++
>   5 files changed, 698 insertions(+)
>   create mode 100644 drivers/iio/adc/Kconfig
>   create mode 100644 drivers/iio/adc/Makefile
>   create mode 100644 drivers/iio/adc/at91_adc.c
>
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index 3ab7d48..47e0920 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -48,4 +48,6 @@ config IIO_CONSUMERS_PER_TRIGGER
>   	This value controls the maximum number of consumers that a
>   	given trigger may handle. Default is 2.
>
> +source "drivers/iio/adc/Kconfig"
> +
>   endif # IIO
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index d5fc57d..eb926a2 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -8,3 +8,5 @@ industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
>   industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
>
>   obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
> +
> +obj-y += adc/
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> new file mode 100644
> index 0000000..9a0df81
> --- /dev/null
> +++ b/drivers/iio/adc/Kconfig
> @@ -0,0 +1,16 @@
> +#
> +# ADC drivers
> +#
> +menu "Analog to digital converters"
> +
> +config AT91_ADC
> +	tristate "Atmel AT91 ADC"
> +	depends on ARCH_AT91
> +	select IIO_BUFFER
> +	select IIO_KFIFO_BUF
> +	select IIO_TRIGGER
> +	select SYSFS
> +	help
> +	  Say yes here to build support for Atmel AT91 ADC.
> +
> +endmenu
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> new file mode 100644
> index 0000000..b62d488
> --- /dev/null
> +++ b/drivers/iio/adc/Makefile
> @@ -0,0 +1,5 @@
> +#
> +# Makefile for IIO ADC drivers
> +#
> +
> +obj-$(CONFIG_AT91_ADC) += at91_adc.o
Please add a newline here.
> \ No newline at end of file
> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
> new file mode 100644
> index 0000000..e5d73b1
> --- /dev/null
> +++ b/drivers/iio/adc/at91_adc.c
> @@ -0,0 +1,673 @@
> +/*
> + * Driver for the ADC present in the Atmel AT91 evaluation boards.
> + *
> + * Copyright 2011 Free Electrons
> + *
> + * Licensed under the GPLv2 or later.
> + */
> +
> +#include<linux/bitmap.h>
> +#include<linux/bitops.h>
> +#include<linux/clk.h>
> +#include<linux/err.h>
> +#include<linux/io.h>
> +#include<linux/interrupt.h>
> +#include<linux/jiffies.h>
> +#include<linux/kernel.h>
> +#include<linux/module.h>
> +#include<linux/platform_device.h>
> +#include<linux/sched.h>
> +#include<linux/slab.h>
> +#include<linux/wait.h>
> +
> +#include<linux/platform_data/at91_adc.h>
> +
> +#include<linux/iio/iio.h>
> +#include<linux/iio/buffer.h>
> +#include<linux/iio/kfifo_buf.h>
> +#include<linux/iio/trigger.h>
> +#include<linux/iio/trigger_consumer.h>
> +
> +#include<mach/at91_adc.h>
> +
> +#define AT91_ADC_CHAN(st, ch) \
> +	(st->registers->channel_base + (ch * 4))
> +#define at91_adc_readl(st, reg) \
> +	(readl_relaxed(st->reg_base + reg))
> +#define at91_adc_writel(st, reg, val) \
> +	(writel_relaxed(val, st->reg_base + reg))
> +
> +struct at91_adc_state {
> +	struct clk		*adc_clk;
> +	u16			*buffer;
> +	unsigned long		channels_mask;
> +	struct clk		*clk;
> +	bool			done;
> +	int			irq;
> +	bool			irq_enabled;
> +	u16			last_value;
> +	struct mutex		lock;
> +	u8			num_channels;
> +	void __iomem		*reg_base;
> +	struct at91_adc_reg_desc *registers;
> +	u8			startup_time;
> +	struct iio_trigger	**trig;
> +	struct at91_adc_trigger	*trigger_list;
> +	u32			trigger_number;
> +	bool			use_external;
> +	u32			vref_mv;
> +	wait_queue_head_t	wq_data_avail;
> +};
> +
> +static irqreturn_t at91_adc_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *idev = pf->indio_dev;
> +	struct at91_adc_state *st = iio_priv(idev);
> +	struct iio_buffer *buffer = idev->buffer;
> +	int i, j = 0;
> +
> +	for (i = 0; i<  idev->masklength; i++) {
> +		if (!test_bit(i, idev->active_scan_mask))
> +			continue;
> +		st->buffer[j] = at91_adc_readl(st, AT91_ADC_CHAN(st, i));
> +		j++;
> +	}
> +
> +	if (idev->scan_timestamp) {
> +		s64 *timestamp = (s64 *)((u8 *)st->buffer +
> +					ALIGN(j, sizeof(s64)));
> +		*timestamp = pf->timestamp;
> +	}
> +
> +	buffer->access->store_to(buffer, (u8 *)st->buffer, pf->timestamp);
> +
> +	iio_trigger_notify_done(idev->trig);
> +	st->irq_enabled = true;
> +
> +	/* Needed to ACK the DRDY interruption */
> +	at91_adc_readl(st, AT91_ADC_LCDR);
> +
> +	enable_irq(st->irq);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t at91_adc_eoc_trigger(int irq, void *private)
> +{
> +	struct iio_dev *idev = private;
> +	struct at91_adc_state *st = iio_priv(idev);
> +	u32 status = at91_adc_readl(st, st->registers->status_register);
> +
> +	if (!(status&  st->registers->drdy_mask))
> +		return IRQ_HANDLED;
> +
> +	if (iio_buffer_enabled(idev)) {
> +		disable_irq_nosync(irq);
> +		st->irq_enabled = false;
> +		iio_trigger_poll(idev->trig, iio_get_time_ns());
> +	} else {
> +		st->last_value = at91_adc_readl(st, AT91_ADC_LCDR);
> +		st->done = true;
> +		wake_up_interruptible(&st->wq_data_avail);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int at91_adc_channel_init(struct iio_dev *idev)
> +{
> +	struct at91_adc_state *st = iio_priv(idev);
> +	struct iio_chan_spec *chan_array, *timestamp;
> +	int bit, idx = 0;
> +
> +	idev->num_channels = bitmap_weight(&st->channels_mask,
> +					   st->num_channels) + 1;
> +
> +	chan_array = devm_kzalloc(&idev->dev,
> +				  ((idev->num_channels + 1) *
> +					sizeof(struct iio_chan_spec)),
> +				  GFP_KERNEL);
> +
> +	if (!chan_array)
> +		return -ENOMEM;
> +
> +	for_each_set_bit(bit,&st->channels_mask, st->num_channels) {
> +		struct iio_chan_spec *chan = chan_array + idx;
> +
> +		chan->type = IIO_VOLTAGE;
> +		chan->indexed = 1;
> +		chan->channel = bit;
> +		chan->scan_index = idx;
> +		chan->scan_type.sign = 'u';
> +		chan->scan_type.realbits = 10;
> +		chan->scan_type.storagebits = 16;
> +		chan->info_mask = IIO_CHAN_INFO_SCALE_SHARED_BIT |
> +			IIO_CHAN_INFO_RAW_SEPARATE_BIT;
> +		idx++;
> +	}
> +	timestamp = chan_array + idx;
> +
> +	timestamp->type = IIO_TIMESTAMP;
> +	timestamp->channel = -1;
> +	timestamp->scan_index = idx;
> +	timestamp->scan_type.sign = 's';
> +	timestamp->scan_type.realbits = 64;
> +	timestamp->scan_type.storagebits = 64;
> +
> +	idev->channels = chan_array;
> +	return idev->num_channels;
> +}
> +
> +static u8 at91_adc_get_trigger_value_by_name(struct iio_dev *idev,
> +					     struct at91_adc_trigger *triggers,
> +					     const char *trigger_name)
> +{
> +	struct at91_adc_state *st = iio_priv(idev);
> +	u8 value = 0;
> +	int i;
> +
> +	for (i = 0; i<  st->trigger_number; i++) {
> +		char *name = kasprintf(GFP_KERNEL,
> +				"%s-dev%d-%s",
> +				idev->name,
> +				idev->id,
> +				triggers[i].name);
> +		if (!name)
> +			return -ENOMEM;
> +
> +		if (strcmp(trigger_name, name) == 0) {
> +			value = triggers[i].value;
> +			kfree(name);
> +			break;
> +		}
> +
> +		kfree(name);
> +	}
> +
> +	return value;
> +}
> +
> +static int at91_adc_configure_trigger(struct iio_trigger *trig, bool state)
> +{
> +	struct iio_dev *idev = trig->private_data;
> +	struct at91_adc_state *st = iio_priv(idev);
> +	struct iio_buffer *buffer = idev->buffer;
> +	struct at91_adc_reg_desc *reg = st->registers;
> +	u32 status = at91_adc_readl(st, reg->trigger_register);
> +	u8 value;
> +	u8 bit;
> +
> +	value = at91_adc_get_trigger_value_by_name(idev,
> +						   st->trigger_list,
> +						   idev->trig->name);
> +	if (value == 0)
> +		return -EINVAL;
> +
> +	if (state) {
> +		st->buffer = kmalloc(idev->scan_bytes, GFP_KERNEL);
> +		if (st->buffer == NULL)
> +			return -ENOMEM;
> +
> +		at91_adc_writel(st, reg->trigger_register,
> +				status | value);
> +
> +		for_each_set_bit(bit, buffer->scan_mask,
> +				 st->num_channels) {
> +			struct iio_chan_spec const *chan = idev->channels + bit;
> +			at91_adc_writel(st, AT91_ADC_CHER,
> +					AT91_ADC_CH(chan->channel));
> +		}
> +
> +		at91_adc_writel(st, AT91_ADC_IER, reg->drdy_mask);
> +
> +	} else {
> +		at91_adc_writel(st, AT91_ADC_IDR, reg->drdy_mask);
> +
> +		at91_adc_writel(st, reg->trigger_register,
> +				status&  ~value);
> +
> +		for_each_set_bit(bit, buffer->scan_mask,
> +				 st->num_channels) {
> +			struct iio_chan_spec const *chan = idev->channels + bit;
> +			at91_adc_writel(st, AT91_ADC_CHDR,
> +					AT91_ADC_CH(chan->channel));
> +		}
> +		kfree(st->buffer);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct iio_trigger_ops at91_adc_trigger_ops = {
> +	.owner = THIS_MODULE,
> +	.set_trigger_state =&at91_adc_configure_trigger,
> +};
> +
> +static struct iio_trigger *at91_adc_allocate_trigger(struct iio_dev *idev,
> +						     struct at91_adc_trigger *trigger)
> +{
> +	struct iio_trigger *trig;
> +	int ret;
> +
> +	trig = iio_trigger_alloc("%s-dev%d-%s", idev->name,
> +				 idev->id, trigger->name);
> +	if (trig == NULL)
> +		return NULL;
> +
> +	trig->dev.parent = idev->dev.parent;
> +	trig->private_data = idev;
> +	trig->ops =&at91_adc_trigger_ops;
> +
> +	ret = iio_trigger_register(trig);
> +	if (ret)
> +		return NULL;
> +
> +	return trig;
> +}
> +
> +static int at91_adc_trigger_init(struct iio_dev *idev)
> +{
> +	struct at91_adc_state *st = iio_priv(idev);
> +	int i, ret;
> +
> +	st->trig = devm_kzalloc(&idev->dev,
> +				st->trigger_number * sizeof(st->trig),
> +				GFP_KERNEL);
> +
> +	if (st->trig == NULL) {
> +		ret = -ENOMEM;
> +		goto error_ret;
> +	}
> +
> +	for (i = 0; i<  st->trigger_number; i++) {
> +		if (st->trigger_list[i].is_external&&  !(st->use_external))
> +			continue;
> +
> +		st->trig[i] = at91_adc_allocate_trigger(idev,
> +							st->trigger_list + i);
> +		if (st->trig[i] == NULL) {
> +			dev_err(&idev->dev,
> +				"Could not allocate trigger %d\n", i);
> +			ret = -ENOMEM;
> +			goto error_trigger;
> +		}
> +	}
> +
> +	return 0;
> +
> +error_trigger:
> +	for (i--; i>= 0; i--) {
> +		iio_trigger_unregister(st->trig[i]);
> +		iio_trigger_free(st->trig[i]);
> +	}
> +error_ret:
> +	return ret;
> +}
> +
> +static void at91_adc_trigger_remove(struct iio_dev *idev)
> +{
> +	struct at91_adc_state *st = iio_priv(idev);
> +	int i;
> +
> +	for (i = 0; i<  st->trigger_number; i++) {
> +		iio_trigger_unregister(st->trig[i]);
> +		iio_trigger_free(st->trig[i]);
> +	}
> +}
> +
> +static const struct iio_buffer_setup_ops at91_adc_buffer_ops = {
> +	.preenable =&iio_sw_buffer_preenable,
> +	.postenable =&iio_triggered_buffer_postenable,
> +	.predisable =&iio_triggered_buffer_predisable,
> +};
> +
> +static int at91_adc_buffer_init(struct iio_dev *idev)
> +{
> +	int ret;
> +
> +	idev->buffer = iio_kfifo_allocate(idev);
> +	if (!idev->buffer) {
> +		ret = -ENOMEM;
> +		goto error_ret;
> +	}
> +
> +	idev->pollfunc = iio_alloc_pollfunc(&iio_pollfunc_store_time,
> +					&at91_adc_trigger_handler,
> +					    IRQF_ONESHOT,
> +					    idev,
> +					    "%s-consumer%d",
> +					    idev->name,
> +					    idev->id);
> +	if (idev->pollfunc == NULL) {
> +		ret = -ENOMEM;
> +		goto error_pollfunc;
> +	}
> +
> +	idev->setup_ops =&at91_adc_buffer_ops;
> +	idev->modes |= INDIO_BUFFER_TRIGGERED;
> +
> +	ret = iio_buffer_register(idev,
> +				  idev->channels,
> +				  idev->num_channels);
> +	if (ret)
> +		goto error_register;
> +
> +	return 0;
> +
> +error_register:
> +	iio_dealloc_pollfunc(idev->pollfunc);
> +error_pollfunc:
> +	iio_kfifo_free(idev->buffer);
> +error_ret:
> +	return ret;
> +}
> +
> +static void at91_adc_buffer_remove(struct iio_dev *idev)
> +{
> +	iio_buffer_unregister(idev);
> +	iio_dealloc_pollfunc(idev->pollfunc);
> +	iio_kfifo_free(idev->buffer);
> +}
> +
> +static int at91_adc_read_raw(struct iio_dev *idev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	struct at91_adc_state *st = iio_priv(idev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&st->lock);
> +
> +		at91_adc_writel(st, AT91_ADC_CHER,
> +				AT91_ADC_CH(chan->channel));
> +		at91_adc_writel(st, AT91_ADC_IER, st->registers->drdy_mask);
> +		at91_adc_writel(st, AT91_ADC_CR, AT91_ADC_START);
> +
> +		ret = wait_event_interruptible_timeout(st->wq_data_avail,
> +						       st->done,
> +						       msecs_to_jiffies(1000));
> +		if (ret == 0)
> +			return -ETIMEDOUT;
> +		else if (ret<  0)
> +			return ret;
> +
> +		*val = st->last_value;
> +
> +		at91_adc_writel(st, AT91_ADC_CHDR,
> +				AT91_ADC_CH(chan->channel));
> +		at91_adc_writel(st, AT91_ADC_IDR, st->registers->drdy_mask);
> +
> +		st->last_value = 0;
> +		st->done = false;
> +		mutex_unlock(&st->lock);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = (st->vref_mv * 1000)>>  chan->scan_type.realbits;
> +		*val2 = 0;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int at91_adc_probe_pdata(struct at91_adc_state *st,
> +				struct platform_device *pdev)
> +{
> +	struct at91_adc_data *pdata = pdev->dev.platform_data;
> +
> +	if (!pdata)
> +		return -EINVAL;
> +
This does look rather like it would be better to just keep a copy of 
pdata around...
Still, not critical at all.
> +	st->use_external = pdata->use_external_triggers;
> +	st->vref_mv = pdata->vref;
> +	st->channels_mask = pdata->channels_used;
> +	st->num_channels = pdata->num_channels;
> +	st->startup_time = pdata->startup_time;
> +	st->trigger_number = pdata->trigger_number;
> +	st->trigger_list = pdata->trigger_list;
> +	st->registers = pdata->registers;
> +
> +	return 0;
> +}
> +
> +static const struct iio_info at91_adc_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw =&at91_adc_read_raw,
> +};
> +
> +static int __devinit at91_adc_probe(struct platform_device *pdev)
> +{
> +	unsigned int prsc, mstrclk, ticks, adc_clk;
> +	int ret;
> +	struct iio_dev *idev;
> +	struct at91_adc_state *st;
> +	struct resource *res;
> +
> +	idev = iio_device_alloc(sizeof(struct at91_adc_state));
> +	if (idev == NULL) {
> +		ret = -ENOMEM;
> +		goto error_ret;
> +	}
> +
> +	st = iio_priv(idev);
> +
> +	ret = at91_adc_probe_pdata(st, pdev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "No platform data available.\n");
> +		ret = -EINVAL;
> +		goto error_free_device;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "No resource defined\n");
> +		ret = -ENXIO;
> +		goto error_ret;
> +	}
> +
> +	platform_set_drvdata(pdev, idev);
> +
> +	idev->dev.parent =&pdev->dev;
> +	idev->name = dev_name(&pdev->dev);
> +	idev->modes = INDIO_DIRECT_MODE;
> +	idev->info =&at91_adc_info;
> +
> +	st->irq = platform_get_irq(pdev, 0);
> +	if (st->irq<  0) {
> +		dev_err(&pdev->dev, "No IRQ ID is designated\n");
> +		ret = -ENODEV;
> +		goto error_free_device;
> +	}
> +
> +	if (!request_mem_region(res->start, resource_size(res),
> +				"AT91 adc registers")) {
> +		dev_err(&pdev->dev, "Resources are unavailable.\n");
> +		ret = -EBUSY;
> +		goto error_free_device;
> +	}
> +
> +	st->reg_base = ioremap(res->start, resource_size(res));
> +	if (!st->reg_base) {
> +		dev_err(&pdev->dev, "Failed to map registers.\n");
> +		ret = -ENOMEM;
> +		goto error_release_mem;
> +	}
> +
> +	/*
> +	 * Disable all IRQs before setting up the handler
> +	 */
> +	at91_adc_writel(st, AT91_ADC_CR, AT91_ADC_SWRST);
> +	at91_adc_writel(st, AT91_ADC_IDR, 0xFFFFFFFF);
> +	ret = request_irq(st->irq,
> +			  at91_adc_eoc_trigger,
> +			  0,
> +			  pdev->dev.driver->name,
> +			  idev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to allocate IRQ.\n");
> +		goto error_unmap_reg;
> +	}
> +
> +	st->clk = clk_get(&pdev->dev, "adc_clk");
> +	if (IS_ERR(st->clk)) {
> +		dev_err(&pdev->dev, "Failed to get the clock.\n");
> +		ret = PTR_ERR(st->clk);
> +		goto error_free_irq;
> +	}
> +
> +	ret = clk_prepare(st->clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Could not prepare the clock.\n");
> +		goto error_free_clk;
> +	}
> +
> +	ret = clk_enable(st->clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Could not enable the clock.\n");
> +		goto error_unprepare_clk;
> +	}
> +
> +	st->adc_clk = clk_get(&pdev->dev, "adc_op_clk");
> +	if (IS_ERR(st->adc_clk)) {
> +		dev_err(&pdev->dev, "Failed to get the ADC clock.\n");
> +		ret = PTR_ERR(st->clk);
> +		goto error_disable_clk;
> +	}
> +
> +	ret = clk_prepare(st->adc_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Could not prepare the ADC clock.\n");
> +		goto error_free_adc_clk;
> +	}
> +
> +	ret = clk_enable(st->adc_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Could not enable the ADC clock.\n");
> +		goto error_unprepare_adc_clk;
> +	}
> +
> +	/*
> +	 * Prescaler rate computation using the formula from the Atmel's
> +	 * datasheet : ADC Clock = MCK / ((Prescaler + 1) * 2), ADC Clock being
> +	 * specified by the electrical characteristics of the board.
> +	 */
> +	mstrclk = clk_get_rate(st->clk);
> +	adc_clk = clk_get_rate(st->adc_clk);
> +	prsc = (mstrclk / (2 * adc_clk)) - 1;
> +
> +	if (!st->startup_time) {
> +		dev_err(&pdev->dev, "No startup time available.\n");
> +		ret = -EINVAL;
> +		goto error_disable_adc_clk;
> +	}
> +
> +	/*
> +	 * Number of ticks needed to cover the startup time of the ADC as
> +	 * defined in the electrical characteristics of the board, divided by 8.
> +	 * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock
> +	 */
> +	ticks = round_up((st->startup_time * adc_clk /
> +			  1000000) - 1, 8) / 8;
> +	at91_adc_writel(st, AT91_ADC_MR,
> +			(AT91_ADC_PRESCAL_(prsc)&  AT91_ADC_PRESCAL) |
> +			(AT91_ADC_STARTUP_(ticks)&  AT91_ADC_STARTUP));
> +
> +	/* Setup the ADC channels available on the board */
> +	ret = at91_adc_channel_init(idev);
> +	if (ret<  0) {
> +		dev_err(&pdev->dev, "Couldn't initialize the channels.\n");
> +		goto error_disable_adc_clk;
> +	}
> +
> +	init_waitqueue_head(&st->wq_data_avail);
> +	mutex_init(&st->lock);
> +
> +	ret = at91_adc_buffer_init(idev);
> +	if (ret<  0) {
> +		dev_err(&pdev->dev, "Couldn't initialize the buffer.\n");
> +		goto error_disable_adc_clk;
> +	}
> +
> +	ret = at91_adc_trigger_init(idev);
> +	if (ret<  0) {
> +		dev_err(&pdev->dev, "Couldn't setup the triggers.\n");
> +		goto error_unregister_buffer;
> +	}
> +
> +	ret = iio_device_register(idev);
> +	if (ret<  0) {
> +		dev_err(&pdev->dev, "Couldn't register the device.\n");
> +		goto error_remove_triggers;
> +	}
> +
> +	return 0;
> +
> +error_remove_triggers:
> +	at91_adc_trigger_remove(idev);
> +error_unregister_buffer:
> +	at91_adc_buffer_remove(idev);
> +error_disable_adc_clk:
> +	clk_disable(st->adc_clk);
> +error_unprepare_adc_clk:
> +	clk_unprepare(st->adc_clk);
> +error_free_adc_clk:
> +	clk_put(st->adc_clk);
> +error_disable_clk:
> +	clk_disable(st->clk);
> +error_unprepare_clk:
> +	clk_unprepare(st->clk);
> +error_free_clk:
> +	clk_put(st->clk);
> +error_free_irq:
> +	free_irq(st->irq, idev);
> +error_unmap_reg:
> +	iounmap(st->reg_base);
> +error_release_mem:
> +	release_mem_region(res->start, resource_size(res));
> +error_free_device:
> +	iio_device_free(idev);
> +error_ret:
> +	return ret;
> +}
> +
> +static int __devexit at91_adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *idev = platform_get_drvdata(pdev);
> +	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	struct at91_adc_state *st = iio_priv(idev);
> +
> +	iio_device_unregister(idev);
> +	at91_adc_trigger_remove(idev);
> +	at91_adc_buffer_remove(idev);
There is clk_disable_unprepare... Could use it though then it's not 
quite as trivial to
check everything lines up between probe and remove.
> +	clk_disable(st->adc_clk);
> +	clk_unprepare(st->adc_clk);
> +	clk_put(st->adc_clk);
> +	clk_disable(st->clk);
> +	clk_unprepare(st->clk);
> +	clk_put(st->clk);
> +	free_irq(st->irq, idev);
> +	iounmap(st->reg_base);
> +	release_mem_region(res->start, resource_size(res));
> +	iio_device_free(idev);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver at91_adc_driver = {
> +	.probe = at91_adc_probe,
> +	.remove = __devexit_p(at91_adc_remove),
> +	.driver = {
> +		   .name = "at91_adc",
> +	},
> +};
> +
> +module_platform_driver(at91_adc_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Atmel AT91 ADC Driver");
> +MODULE_AUTHOR("Maxime Ripard<maxime.ripard@free-electrons.com>");