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

Jonathan Cameron
2011-11-04T10:27:12Z

On 11/03/2011 10:11 AM, Maxime Ripard wrote:
> Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
> Cc: Patrice Vilchez <patrice.vilchez@atmel.com>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
> drivers/staging/iio/adc/Kconfig | 6 +
> drivers/staging/iio/adc/Makefile | 1 +
> drivers/staging/iio/adc/at91adc.c | 310 +++++++++++++++++++++++++++++++++++++
> 3 files changed, 317 insertions(+), 0 deletions(-)
> create mode 100644 drivers/staging/iio/adc/at91adc.c
>
> diff --git a/drivers/staging/iio/adc/Kconfig b/drivers/staging/iio/adc/Kconfig
> index d9decea..c384894 100644
> --- a/drivers/staging/iio/adc/Kconfig
> +++ b/drivers/staging/iio/adc/Kconfig
> @@ -169,6 +169,12 @@ config AD7280
> To compile this driver as a module, choose M here: the
> module will be called ad7280a
>
> +config AT91ADC
> + tristate "Atmel AT91 ADC"
> + depends on SYSFS && ARCH_AT91
> + help
> + Say yes here to build support for Atmel AT91 ADC.
> +
> config MAX1363
> tristate "Maxim max1363 ADC driver"
> depends on I2C
> diff --git a/drivers/staging/iio/adc/Makefile b/drivers/staging/iio/adc/Makefile
> index ceee7f3..d250d06 100644
> --- a/drivers/staging/iio/adc/Makefile
> +++ b/drivers/staging/iio/adc/Makefile
> @@ -37,3 +37,4 @@ obj-$(CONFIG_AD7192) += ad7192.o
> obj-$(CONFIG_ADT7310) += adt7310.o
> obj-$(CONFIG_ADT7410) += adt7410.o
> obj-$(CONFIG_AD7280) += ad7280a.o
> +obj-$(CONFIG_AT91ADC) += at91adc.o
> diff --git a/drivers/staging/iio/adc/at91adc.c b/drivers/staging/iio/adc/at91adc.c
> new file mode 100644
> index 0000000..acf656d
> --- /dev/null
> +++ b/drivers/staging/iio/adc/at91adc.c
> @@ -0,0 +1,310 @@
> +/*
> + * Driver for the TouchScreen ADC Controller present in the Atmel AT91
> + * evaluation boards.
I'd add something here to make it clear that it isn't being used for
touchscreen input in this driver.
> + *
> + * Copyright 2011 Free Electrons
> + *
> + * Licensed under the GPLv2 or later.
> + */
> +
> +#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 "../iio.h"
> +
> +#include <mach/at91_adc.h>
> +#include <mach/board.h>
> +
I'd marginally prefer to see these as inlines rather than macros. Far
from critical though!
> +#define at91adc_reg_read(base, reg) readl_relaxed((base) + (reg))
> +#define at91adc_reg_write(base, reg, val) writel_relaxed((val), (base) + (reg))
> +
> +struct at91adc_state {
> + struct clk *clk;
> + bool done;
> + struct mutex lock;
why hold a local pointer? Just put these
directly into iio_dev->channels.
> + struct iio_chan_spec *channels;
likewise, we already have iio_dev->num_channels.
> + int nb_chan;

> + int irq;
> + wait_queue_head_t wq_data_avail;
cryptic element. Nice to have everything documented, but
this one is most important as it isn't self explanatory.
> + u16 lcdr;
> + void __iomem *reg_base;
> + unsigned int vref_mv;
> +};
> +
> +static irqreturn_t at91adc_eoc_trigger(int irq, void *private)
> +{
> + int chan;
> + struct at91adc_state *st = private;
> + unsigned int status = at91adc_reg_read(st->reg_base, AT91_ADC_SR);
> +
> + if (!(status & AT91_ADC_DRDY))
> + return IRQ_HANDLED;
> +
extra unneeded brackets for the for loop.
> + for (chan = 0; chan < st->nb_chan; chan++) {
> + if (status & AT91_ADC_EOC(chan)) {
> + st->done = true;
> + st->lcdr = at91adc_reg_read(st->reg_base,
> + AT91_ADC_CHR(chan));
> + }
> + }
> + wake_up_interruptible(&st->wq_data_avail);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int at91adc_channel_init(struct at91adc_state *st,
> + struct at91_adc_data *pdata)
> +{
> + int i, idx = 0;
> + st->channels = kcalloc(pdata->num_channels_used,
> + sizeof(struct iio_chan_spec), GFP_KERNEL);
> + if (st->channels == NULL)
> + return -ENOMEM;
> +
Again, extra brackets. Also, some wrong spacing for the if.
can you run checkpatch.pl over this again and make sure you
have fixed everything.
> + for (i = 0; i < st->nb_chan; i++) {
as stated for the previous patch, this should be a bitmap rather
than array of u8's. You can then use for_each_bit_set
to clean this code up nicely ;)
> + if(pdata->channels_used[i]) {
> + struct iio_chan_spec *chan = st->channels + idx;
> + chan->type = IIO_VOLTAGE;
> + chan->indexed = 1;
> + chan->channel = i;
> + chan->scan_type.sign = 's';
> + chan->scan_type.realbits = 10;
> + chan->scan_type.storagebits = 32;
That is pretty inefficient storage! If we do implement buffering
on this, given mass reads don't look to be quicker, we'll just
munge it down to 16 bits.

> + chan->scan_type.shift = 0;
don't bother initialising this value as it is zero (and that's an
obvious default).
> + chan->info_mask = IIO_CHAN_INFO_SCALE_SHARED_BIT;
> + ++idx;
> + }
> + }
> +
> + return st->nb_chan;
> +}
> +
> +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;
> +
> + switch (mask) {
> + case 0:
> + mutex_lock(&st->lock);
> +
> + at91adc_reg_write(st->reg_base, AT91_ADC_CHER,
> + AT91_ADC_CH(chan->channel));
> + at91adc_reg_write(st->reg_base, AT91_ADC_IER,
> + AT91_ADC_EOC(chan->channel));
> + at91adc_reg_write(st->reg_base, AT91_ADC_CR, AT91_ADC_START);
> +
> + wait_event_interruptible_timeout(st->wq_data_avail, st->done,
> + msecs_to_jiffies(10 * 1000));
> + *val = st->lcdr;
> +
> + at91adc_reg_write(st->reg_base, AT91_ADC_CHDR,
> + AT91_ADC_CH(chan->channel));
> + at91adc_reg_write(st->reg_base, AT91_ADC_IDR,
> + AT91_ADC_EOC(chan->channel));
> +
> + st->lcdr = 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_allocate_device(sizeof(struct at91adc_state));
sizeof(*st) is a little neater?
> + if (idev == NULL) {
I'm not sure this message adds anything or is even necessarily
correct as that function doesn't just allocate memory!
> + dev_err(&pdev->dev, "Failed to allocate memory.\n");
> + ret = -ENOMEM;
> + 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 = &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->reg_base, AT91_ADC_CR, AT91_ADC_SWRST);
> + at91adc_reg_write(st->reg_base, AT91_ADC_IDR, 0xFFFFFFFF);
> + ret = request_irq(st->irq,
> + at91adc_eoc_trigger, 0, pdev->dev.driver->name, st);
> + 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;
> + }
> +
> + 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;
> + }
> +
> + ticks = round_up((pdata->startup_time * pdata->adc_clock /
> + 1000000) - 1, 8) / 8;
> + at91adc_reg_write(st->reg_base, 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 */
> + st->nb_chan = pdata->num_channels;
> + ret = at91adc_channel_init(st, pdata);
> + if (ret < 0) {
no brackets please. Again, checkpatch would probably have shouted
about this.
> + goto error_free_clk;
> + }
> +
This is what I meant when I asked why you have two copies of the
pointer and count?
> + idev->channels = st->channels;
> + idev->num_channels = pdata->num_channels_used;
> +
> + init_waitqueue_head(&st->wq_data_avail);
> + mutex_init(&st->lock);
> +
> + st->vref_mv = pdata->vref;
> +
> + ret = iio_device_register(idev);
again incorrect brackets for the code style.
> + if (ret < 0) {
unwind the channel init?
> + goto error_free_clk;
> + }
> +
> + return 0;
> +
> +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_free_device(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);
Free channels array?
> + free_irq(st->irq, st);
> + iounmap(st->reg_base);
> + release_mem_region(res->start, resource_size(res));
> + iio_free_device(idev);
> +
> + return 0;
> +}
> +
> +static struct platform_driver at91adc_driver = {
> + .probe = at91adc_probe,
> + .remove = __devexit_p(at91adc_remove),
> + .driver = {
> + .name = "at91adc",
> + },
> +};
> +
> +static int __init at91adc_init(void)
> +{
> + return platform_driver_register(&at91adc_driver);
> +}
> +
> +static void __exit at91adc_exit(void)
> +{
> + platform_driver_unregister(&at91adc_driver);
> +}
> +

Some neat boiler plate removal stuff was just merged for
platform drivers. See module_platform_driver in include/linux/platform.h

Definitely want to use that! I'm hoping the spi and i2c versions
turn up soon as it will save us a lot of silly cut and paste code.
> +module_init(at91adc_init);
> +module_exit(at91adc_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Atmel AT91 ADC Driver");
> +MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");