AT91: Add a driver for the ADC

Cc Nicolas Ferre <[email protected]>

Cc Patrice Vilchez <[email protected]>

Cc Jean-Christophe Plagniol-Villard <[email protected]>

Cc Thomas Petazzoni <[email protected]>

Signed-off-by Maxime Ripard <[email protected]>

Acked-by Jonathan Cameron <[email protected]>

Acked-by Nicolas Ferre <[email protected]>

Reviewed-by Marek Vasut <[email protected]>

---
 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

drivers/iio/adc/Kconfig +6 -0

index 3d97b21..74f4d9f 100644
@@ -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

drivers/iio/adc/Makefile +3 -1

index c197334..776b56f 100644
@@ -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

drivers/iio/adc/at91adc.c new file +97 -0

new file mode 100644
index 0000000..4652d73
@@ -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)
+{

drivers/iio/adc/at91adc.c new file +22 -0

+
+	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,

drivers/iio/adc/at91adc.c new file +187 -0

+		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 protected]>");

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.

Cc Nicolas Ferre <[email protected]>

Cc Patrice Vilchez <[email protected]>

Cc Thomas Petazzoni <[email protected]>

Signed-off-by Maxime Ripard <[email protected]>

Signed-off-by Nicolas Ferre <[email protected]>

---
 arch/arm/mach-at91/at91sam9260_devices.c |   55 ++++++++++++++++++++++++++++++
 arch/arm/mach-at91/board-sam9g20ek.c     |   11 ++++++
 2 files changed, 66 insertions(+), 0 deletions(-)

arch/arm/mach-at91/at91sam9260_devices.c +55 -0

index 39f81f4..3b754ba 100644
@@ -1312,6 +1312,61 @@ void __init at91_add_device_cf(struct at91_cf_data *data)
 void __init at91_add_device_cf(struct at91_cf_data * data) {}
 #endif
 
+/* --------------------------------------------------------------------
+ *  ADCs
+ * -------------------------------------------------------------------- */
+
+#if defined(CONFIG_IIO_AT91ADC) || defined(CONFIG_IIO_AT91ADC_MODULE)
+static struct at91_adc_data adc_data;
+
+static struct resource adc_resources[] = {
+	[0] = {
+		.start	= AT91SAM9260_BASE_ADC,
+		.end	= AT91SAM9260_BASE_ADC + SZ_16K - 1,
+		.flags	= IORESOURCE_MEM,
+	},
+	[1] = {
+		.start	= AT91SAM9260_ID_ADC,
+		.end	= AT91SAM9260_ID_ADC,
+		.flags	= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device at91_adc_device = {
+	.name		= "at91adc",
+	.id		= -1,
+	.dev		= {
+				.platform_data		= &adc_data,
+	},
+	.resource	= adc_resources,
+	.num_resources	= ARRAY_SIZE(adc_resources),
+};
+
+void __init at91_add_device_adc(struct at91_adc_data *data)
+{
+	if (!data)
+		return;
+
+	if (test_bit(0, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC0, 0);
+	if (test_bit(1, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC1, 0);
+	if (test_bit(2, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC2, 0);
+	if (test_bit(3, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC3, 0);
+
+	data->adc_clock = 5000000;
+	data->num_channels = 4;
+	data->startup_time = 10;
+
+	adc_data = *data;
+	platform_device_register(&at91_adc_device);
+}
+#else
+void __init at91_add_device_adc(struct at91_adc_data *data) {}
+#endif
+
 /* -------------------------------------------------------------------- */
 /*
  * These devices are always present and don't need any board-specific

arch/arm/mach-at91/board-sam9g20ek.c +0 -0

index 817f59d..e34d41a 100644
@@ -314,6 +314,15 @@ static void __init ek_add_device_buttons(void)
 static void __init ek_add_device_buttons(void) {}

arch/arm/mach-at91/board-sam9g20ek.c +3 -0

+
 #if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
 static struct regulator_consumer_supply ek_audio_consumer_supplies[] = {
 	REGULATOR_SUPPLY("AVDD", "0-001b"),

@@ -389,6 +398,8 @@ static void __init ek_board_init(void)
 	ek_add_device_gpio_leds();
 	/* Push Buttons */
 	ek_add_device_buttons();
+	/* ADCs */
+	at91_add_device_adc(&ek_adc_data);
 	/* PCK0 provides MCLK to the WM8731 */
 	at91_set_B_periph(AT91_PIN_PC1, 0);
 	/* SSC (for WM8731) */

Quoted 4 lines · Maxime Ripard

Cc Nicolas Ferre <[email protected]>

Cc Patrice Vilchez <[email protected]>

Cc Thomas Petazzoni <[email protected]>

I'm happy with this, but the question comes of how to merge it with minimal conflicts. Clearly 2/3 is entirely in IIO so easy enough but is dependent on 1/3. 3/3 is entirely in the at91 maintainers domain but is also dependent on 1/3.

What do people what to do?

Quoted 79 lines

Signed-off-by Maxime Ripard <[email protected]>

Signed-off-by Nicolas Ferre <[email protected]>

---
 arch/arm/mach-at91/at91sam9260_devices.c |   55 ++++++++++++++++++++++++++++++
 arch/arm/mach-at91/board-sam9g20ek.c     |   11 ++++++
 2 files changed, 66 insertions(+), 0 deletions(-)

arch/arm/mach-at91/at91sam9260_devices.c +55 -0

index 39f81f4..3b754ba 100644
@@ -1312,6 +1312,61 @@ void __init at91_add_device_cf(struct at91_cf_data *data)
 void __init at91_add_device_cf(struct at91_cf_data * data) {}
 #endif
 
+/* --------------------------------------------------------------------
+ *  ADCs
+ * -------------------------------------------------------------------- */
+
+#if defined(CONFIG_IIO_AT91ADC) || defined(CONFIG_IIO_AT91ADC_MODULE)
+static struct at91_adc_data adc_data;
+
+static struct resource adc_resources[] = {
+	[0] = {
+		.start	= AT91SAM9260_BASE_ADC,
+		.end	= AT91SAM9260_BASE_ADC + SZ_16K - 1,
+		.flags	= IORESOURCE_MEM,
+	},
+	[1] = {
+		.start	= AT91SAM9260_ID_ADC,
+		.end	= AT91SAM9260_ID_ADC,
+		.flags	= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device at91_adc_device = {
+	.name		= "at91adc",
+	.id		= -1,
+	.dev		= {
+				.platform_data		= &adc_data,
+	},
+	.resource	= adc_resources,
+	.num_resources	= ARRAY_SIZE(adc_resources),
+};
+
+void __init at91_add_device_adc(struct at91_adc_data *data)
+{
+	if (!data)
+		return;
+
+	if (test_bit(0, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC0, 0);
+	if (test_bit(1, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC1, 0);
+	if (test_bit(2, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC2, 0);
+	if (test_bit(3, &data->channels_used))
+		at91_set_A_periph(AT91_PIN_PC3, 0);
+
+	data->adc_clock = 5000000;
+	data->num_channels = 4;
+	data->startup_time = 10;
+
+	adc_data = *data;
+	platform_device_register(&at91_adc_device);
+}
+#else
+void __init at91_add_device_adc(struct at91_adc_data *data) {}
+#endif
+
 /* -------------------------------------------------------------------- */
 /*
  * These devices are always present and don't need any board-specific

arch/arm/mach-at91/board-sam9g20ek.c +0 -0

index 817f59d..e34d41a 100644
@@ -314,6 +314,15 @@ static void __init ek_add_device_buttons(void)
 static void __init ek_add_device_buttons(void) {}

arch/arm/mach-at91/board-sam9g20ek.c static void __init ek_add_device_buttons(void) · line 324

Quoted 10 lines

arch/arm/mach-at91/board-sam9g20ek.c +8 -0

 #endif
 
+/*
+ * ADCs
+ */
+
+static struct at91_adc_data ek_adc_data = {
+	.channels_used = BIT(0) | BIT(1) | BIT(2) | BIT(3),
+	.vref = 3300,
+};

Feels like this should be marked as __initdata given it gets copied in the below function?

Quoted 13 lines

arch/arm/mach-at91/board-sam9g20ek.c +3 -0

+
 #if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
 static struct regulator_consumer_supply ek_audio_consumer_supplies[] = {
 	REGULATOR_SUPPLY("AVDD", "0-001b"),

@@ -389,6 +398,8 @@ static void __init ek_board_init(void)
 	ek_add_device_gpio_leds();
 	/* Push Buttons */
 	ek_add_device_buttons();
+	/* ADCs */
+	at91_add_device_adc(&ek_adc_data);
 	/* PCK0 provides MCLK to the WM8731 */
 	at91_set_B_periph(AT91_PIN_PC1, 0);
 	/* SSC (for WM8731) */