Subject: [PATCH 2/3] ARM: AT91: IIO: Add AT91 ADC driver.

From: [email-masked] (Jonathan Cameron)
Date: Mon, 14 Nov 2011 21:32:02 +0000

On 11/14/2011 05:30 PM, Maxime Ripard wrote:
> Cc: Nicolas Ferre <[email-masked]>
> Cc: Patrice Vilchez <[email-masked]>
> Cc: Jean-Christophe Plagniol-Villard <[email-masked]>
> Cc: Thomas Petazzoni <[email-masked]>

Just one more query on the IIO_CHAN_INFO_SCALE read.
Sorry, missed this last time.  Its late so I may be going
mad but the units seem out by 1000.

Also mysterious short as return value type in read_raw.

If I take this through my tree, I'll switch the ack below
for a sign off.

Jonathan
> 
> Signed-off-by: Maxime Ripard <[email-masked]>
> Acked-by: Jonathan Cameron <[email-masked]>
> Acked-by: Nicolas Ferre <[email-masked]>
> Reviewed-by: Marek Vasut <[email-masked]>
> ---
>  drivers/iio/adc/Kconfig   |    6 +
>  drivers/iio/adc/Makefile  |    4 +-
>  drivers/iio/adc/at91adc.c |  326 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 335 insertions(+), 1 deletions(-)
>  create mode 100644 drivers/iio/adc/at91adc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 3d97b21..74f4d9f 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -14,6 +14,12 @@ config IIO_AD799X
>  	  i2c analog to digital convertors (ADC). Provides direct access
>  	  via sysfs.
>  
> +config IIO_AT91ADC
> +	tristate "Atmel AT91 ADC"
> +	depends on SYSFS && ARCH_AT91
> +	help
> +	  Say yes here to build support for Atmel AT91 ADC.
> +
>  config IIO_MAX1363
>  	tristate "Maxim max1363 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index c197334..776b56f 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -6,4 +6,6 @@ iio_ad799x-y := ad799x_core.o
>  obj-$(CONFIG_IIO_AD799X) += iio_ad799x.o
>  
>  iio_max1363-y := max1363_core.o
> -obj-$(CONFIG_IIO_MAX1363) += iio_max1363.o
> \ No newline at end of file
> +obj-$(CONFIG_IIO_MAX1363) += iio_max1363.o
> +
> +obj-$(CONFIG_IIO_AT91ADC) += at91adc.o
> diff --git a/drivers/iio/adc/at91adc.c b/drivers/iio/adc/at91adc.c
> new file mode 100644
> index 0000000..4652d73
> --- /dev/null
> +++ b/drivers/iio/adc/at91adc.c
> @@ -0,0 +1,326 @@
> +/*
> + * 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/slab.h>
> +#include <linux/wait.h>
> +
> +#include <linux/iio/iio.h>
> +
> +#include <mach/at91_adc.h>
> +#include <mach/board.h>
> +
> +struct at91adc_state {
> +	struct clk *clk;
> +	bool done;
> +	struct mutex lock;
> +	int irq;
> +	wait_queue_head_t wq_data_avail;
> +	u16 last_value;
> +	void __iomem *reg_base;
> +	unsigned int vref_mv;
> +};
> +
> +static inline u32 at91adc_reg_read(struct at91adc_state *st, u8 reg)
> +{
> +	return readl_relaxed(st->reg_base + reg);
> +}
> +
> +static inline void at91adc_reg_write(struct at91adc_state *st, u8 reg, u32 val)
> +{
> +	writel_relaxed(val, st->reg_base + reg);
> +}
> +
> +static irqreturn_t at91adc_eoc_trigger(int irq, void *private)
> +{
> +	struct iio_dev *idev = private;
> +	struct at91adc_state *st = iio_priv(idev);
> +	unsigned int status = at91adc_reg_read(st, AT91_ADC_SR);
> +
> +	if (!(status & AT91_ADC_DRDY))
> +		return IRQ_HANDLED;
> +
> +	if (status & ((2 << idev->num_channels) - 1)) {
> +		st->done = true;
> +		st->last_value = at91adc_reg_read(st, AT91_ADC_LCDR);
> +	}
> +
> +	wake_up_interruptible(&st->wq_data_avail);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int at91adc_channel_init(struct iio_dev *idev,
> +				struct at91_adc_data *pdata)
> +{
> +	struct iio_chan_spec *chan_array;
> +	int bit, idx = 0;
> +
> +	idev->num_channels = bitmap_weight(&pdata->channels_used,
> +					   pdata->num_channels);
> +	chan_array = kcalloc(idev->num_channels, sizeof(struct iio_chan_spec),
> +			     GFP_KERNEL);
> +
> +	if (chan_array == NULL)
> +		return -ENOMEM;
> +
> +	for_each_set_bit(bit, &pdata->channels_used, pdata->num_channels) {
> +		struct iio_chan_spec *chan = chan_array + idx;
> +		chan->type = IIO_VOLTAGE;
> +		chan->indexed = 1;
> +		chan->channel = bit;
> +		chan->scan_type.sign = 'u';
> +		chan->scan_type.realbits = 10;
> +		chan->info_mask = IIO_CHAN_INFO_SCALE_SHARED_BIT;
> +		idx++;
> +	}
> +
> +	idev->channels = chan_array;
> +	return idev->num_channels;
> +}
> +
> +static void at91adc_channel_remove(struct iio_dev *idev)
> +{
> +	kfree(idev->channels);
> +}
> +
> +static int at91adc_read_raw(struct iio_dev *idev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct at91adc_state *st = iio_priv(idev);
> +	unsigned int scale_uv;
> +	short ret;
Why not int?
> +
> +	switch (mask) {
> +	case 0:
> +		mutex_lock(&st->lock);
> +
> +		at91adc_reg_write(st, AT91_ADC_CHER,
> +				  AT91_ADC_CH(chan->channel));
> +		at91adc_reg_write(st, AT91_ADC_IER,
> +				  AT91_ADC_EOC(chan->channel));
> +		at91adc_reg_write(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;
> +
> +		at91adc_reg_write(st, AT91_ADC_CHDR,
> +				  AT91_ADC_CH(chan->channel));
> +		at91adc_reg_write(st, AT91_ADC_IDR,
> +				  AT91_ADC_EOC(chan->channel));
> +
> +		st->last_value = 0;
> +		st->done = false;
> +		mutex_unlock(&st->lock);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
There is something a little missleading in the scaling here.
If scale_uv is in microvolts as the name would suggest, then
*val = scale_uv/1000000
and *val2 = (scale % 1000000);
To end up with the right units (I think).  Please just check this over.

> +		scale_uv = (st->vref_mv * 1000) >> chan->scan_type.realbits;
> +		*val = scale_uv / 1000;
> +		*val2 = (scale_uv % 1000) * 1000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info at91adc_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = &at91adc_read_raw,
> +};
> +
> +static int __devinit at91adc_probe(struct platform_device *pdev)
> +{
> +	unsigned int prsc, mstrclk, ticks;
> +	int ret;
> +	struct iio_dev *idev;
> +	struct at91adc_state *st;
> +	struct resource *res;
> +	struct at91_adc_data *pdata = pdev->dev.platform_data;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "No resource defined\n");
> +		ret = -ENXIO;
> +		goto error_ret;
> +	}
> +
> +	idev = iio_device_allocate(sizeof(struct at91adc_state));
> +	if (idev == NULL) {
> +		ret = -ENOMEM;
> +		goto error_ret;
> +	}
> +
> +	platform_set_drvdata(pdev, idev);
> +
> +	idev->dev.parent = &pdev->dev;
> +	idev->name = dev_name(&pdev->dev);
> +	idev->info = &at91adc_info;
> +
> +	st = iio_priv(idev);
> +	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
> +	 */
> +	at91adc_reg_write(st, AT91_ADC_CR, AT91_ADC_SWRST);
> +	at91adc_reg_write(st, AT91_ADC_IDR, 0xFFFFFFFF);
> +	ret = request_irq(st->irq,
> +			  at91adc_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;
> +	}
> +
> +	clk_enable(st->clk);
> +	mstrclk = clk_get_rate(st->clk);
> +
> +	if (!pdata) {
> +		dev_err(&pdev->dev, "No platform data available.\n");
> +		ret = -EINVAL;
> +		goto error_free_clk;
> +	}
> +
> +	if (!pdata->adc_clock) {
> +		dev_err(&pdev->dev, "No ADCClock available.\n");
> +		ret = -EINVAL;
> +		goto error_free_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.
> +	 */
> +	prsc = (mstrclk / (2 * pdata->adc_clock)) - 1;
> +
> +	if (!pdata->startup_time) {
> +		dev_err(&pdev->dev, "No startup time available.\n");
> +		ret = -EINVAL;
> +		goto error_free_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((pdata->startup_time * pdata->adc_clock /
> +			  1000000) - 1, 8) / 8;
> +	at91adc_reg_write(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 = at91adc_channel_init(idev, pdata);
> +	if (ret < 0)
> +		goto error_free_clk;
> +
> +	init_waitqueue_head(&st->wq_data_avail);
> +	mutex_init(&st->lock);
> +
> +	st->vref_mv = pdata->vref;
> +
> +	ret = iio_device_register(idev);
> +	if (ret < 0)
> +		goto error_free_channels;
> +
> +	return 0;
> +
> +error_free_channels:
> +	at91adc_channel_remove(idev);
> +error_free_clk:
> +	clk_disable(st->clk);
> +	clk_put(st->clk);
> +error_free_irq:
> +	free_irq(st->irq, st);
> +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 at91adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *idev = platform_get_drvdata(pdev);
> +	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	struct at91adc_state *st = iio_priv(idev);
> +
> +	iio_device_unregister(idev);
> +	at91adc_channel_remove(idev);
> +	clk_disable(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 at91adc_driver = {
> +	.probe = at91adc_probe,
> +	.remove = __devexit_p(at91adc_remove),
> +	.driver = {
> +		   .name = "at91adc",
> +	},
> +};
> +
> +module_platform_driver(at91adc_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Atmel AT91 ADC Driver");
> +MODULE_AUTHOR("Maxime Ripard <[email-masked]>");