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

Maxime Ripard
2011-11-14T10:06:32Z

Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Patrice Vilchez <patrice.vilchez@atmel.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
---
drivers/iio/adc/Kconfig | 6 +
drivers/iio/adc/Makefile | 4 +-
drivers/iio/adc/at91adc.c | 323 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 332 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..eee591d
--- /dev/null
+++ b/drivers/iio/adc/at91adc.c
@@ -0,0 +1,323 @@
+/*
+ * 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;
+
+ 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@free-electrons.com>");
--
1.7.4.1