[PATCH 2/3] ARM: AT91: IIO: Add AT91 ADC driver.
Jonathan Cameron
jic23 at kernel.org
Thu Nov 10 12:35:09 EST 2011
On 11/09/2011 10:19 AM, Maxime Ripard wrote:
> Cc: Nicolas Ferre <nicolas.ferre at atmel.com>
> Cc: Patrice Vilchez <patrice.vilchez at atmel.com>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj at jcrosoft.com>
> Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
>
One little comment / query inline. I'm happy with this either way
though. Beware as you are dependent on a series under review though
and it's always possible little things in there might change!
> Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
Acked-by: Jonathan Cameron <jic23 at cam.ac.uk>
> ---
> 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..6aef5d6
> --- /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)
> +{
> + int chan;
> + 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;
> +
> + for (chan = 0; chan < idev->num_channels; chan++)
Given we know only one bit should be set, it really feels like there
should be
a cleaner way of doing this. Could it use find_first_bit(&status,
idev->num_channels)?
It kind of bypasses the defines though so it's far from clean in that sense.
> + if (status & AT91_ADC_EOC(chan)) {
The logic in here very much assumes that only one channel is being converted
and the interrupt indicates that one of the channels has finished.
Hence logically this st->done doesn't need to be in the loop.
> + st->done = true;
> + st->last_value = at91adc_reg_read(st,
> + AT91_ADC_CHR(chan));
> + }
> +
> + 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;
> +
> + 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 == -ERESTARTSYS)
> + break;
> +
> + *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:
> + 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 <maxime.ripard at free-electrons.com>");
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