Commit b3201b56 authored by Stefan Roese's avatar Stefan Roese Committed by Greg Kroah-Hartman
Browse files

staging:iio:adc: Add SPEAr ADC driver 



This patch implements the basic single data conversion support for
the SPEAr600 SoC ADC. The register layout of SPEAr600 differs a bit
from other SPEAr SoC variants (e.g. SPEAr3xx). These differences are
handled via DT compatible testing. Resulting in a multi-arch binary.

This driver is currently tested only on SPEAr600. Future patches may add
support for other SoC variants (SPEAr3xx) and features like software
buffer or DMA.

Signed-off-by: default avatarStefan Roese <sr@denx.de>
Acked-by: default avatarJonathan Cameron <jic23@kernel.org>
Acked-by: default avatarViresh Kumar <viresh.kumar@st.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6d59ba2f

Documentation/devicetree/bindings/staging/iio/adc/spear-adc.txt

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* ST SPEAr ADC device driver



Required properties:

- compatible: Should be "st,spear600-adc"

- reg: Address and length of the register set for the device

- interrupt-parent: Should be the phandle for the interrupt controller

  that services interrupts for this device

- interrupts: Should contain the ADC interrupt

- sampling-frequency: Default sampling frequency



Optional properties:

- vref-external: External voltage reference in milli-volts. If omitted

  the internal voltage reference will be used.

- average-samples: Number of samples to generate an average value. If

  omitted, single data conversion will be used.



Examples:



	adc: adc@d8200000 {

		compatible = "st,spear600-adc";

		reg = <0xd8200000 0x1000>;

		interrupt-parent = <&vic1>;

		interrupts = <6>;

		sampling-frequency = <5000000>;

		vref-external = <2500>;	/* 2.5V VRef */

	};

drivers/staging/iio/adc/Kconfig

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@@ -202,4 +202,11 @@ config LPC32XX_ADC 
	  touchscreen driver, so you can only select one of the two drivers

	  (lpc32xx_adc or lpc32xx_ts). Provides direct access via sysfs.



config SPEAR_ADC

	tristate "ST SPEAr ADC"

	depends on PLAT_SPEAR

	help

	  Say yes here to build support for the integrated ADC inside the

	  ST SPEAr SoC. Provides direct access via sysfs.



endmenu

drivers/staging/iio/adc/Makefile

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@@ -38,3 +38,4 @@ obj-$(CONFIG_ADT7310) += adt7310.o 
obj-$(CONFIG_ADT7410) += adt7410.o

obj-$(CONFIG_AD7280) += ad7280a.o

obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o

obj-$(CONFIG_SPEAR_ADC) += spear_adc.o

drivers/staging/iio/adc/spear_adc.c

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/*

 * ST SPEAr ADC driver

 *

 * Copyright 2012 Stefan Roese <sr@denx.de>

 *

 * Licensed under the GPL-2.

 */



#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/interrupt.h>

#include <linux/device.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/io.h>

#include <linux/clk.h>

#include <linux/err.h>

#include <linux/completion.h>

#include <linux/of.h>

#include <linux/of_address.h>



#include "../iio.h"

#include "../sysfs.h"



/*

 * SPEAR registers definitions

 */



#define SCAN_RATE_LO(x)		((x) & 0xFFFF)

#define SCAN_RATE_HI(x)		(((x) >> 0x10) & 0xFFFF)

#define CLK_LOW(x)		(((x) & 0xf) << 0)

#define CLK_HIGH(x)		(((x) & 0xf) << 4)



/* Bit definitions for SPEAR_ADC_STATUS */

#define START_CONVERSION	(1 << 0)

#define CHANNEL_NUM(x)		((x) << 1)

#define ADC_ENABLE		(1 << 4)

#define AVG_SAMPLE(x)		((x) << 5)

#define VREF_INTERNAL		(1 << 9)



#define DATA_MASK		0x03ff

#define DATA_BITS		10



#define MOD_NAME "spear-adc"



#define ADC_CHANNEL_NUM		8



#define CLK_MIN			2500000

#define CLK_MAX			20000000



struct adc_regs_spear3xx {

	u32 status;

	u32 average;

	u32 scan_rate;

	u32 clk;	/* Not avail for 1340 & 1310 */

	u32 ch_ctrl[ADC_CHANNEL_NUM];

	u32 ch_data[ADC_CHANNEL_NUM];

};



struct chan_data {

	u32 lsb;

	u32 msb;

};



struct adc_regs_spear6xx {

	u32 status;

	u32 pad[2];

	u32 clk;

	u32 ch_ctrl[ADC_CHANNEL_NUM];

	struct chan_data ch_data[ADC_CHANNEL_NUM];

	u32 scan_rate_lo;

	u32 scan_rate_hi;

	struct chan_data average;

};



struct spear_adc_info {

	struct device_node *np;

	struct adc_regs_spear3xx __iomem *adc_base_spear3xx;

	struct adc_regs_spear6xx __iomem *adc_base_spear6xx;

	struct clk *clk;

	struct completion completion;

	u32 current_clk;

	u32 sampling_freq;

	u32 avg_samples;

	u32 vref_external;

	u32 value;

};



/*

 * Functions to access some SPEAr ADC register. Abstracted into

 * static inline functions, because of different register offsets

 * on different SoC variants (SPEAr300 vs SPEAr600 etc).

 */

static void spear_adc_set_status(struct spear_adc_info *info, u32 val)

{

	__raw_writel(val, &info->adc_base_spear6xx->status);

}



static void spear_adc_set_clk(struct spear_adc_info *info, u32 val)

{

	u32 clk_high, clk_low, count;

	u32 apb_clk = clk_get_rate(info->clk);



	count = (apb_clk + val - 1) / val;

	clk_low = count / 2;

	clk_high = count - clk_low;

	info->current_clk = apb_clk / count;



	__raw_writel(CLK_LOW(clk_low) | CLK_HIGH(clk_high),

		     &info->adc_base_spear6xx->clk);

}



static void spear_adc_set_ctrl(struct spear_adc_info *info, int n,

			       u32 val)

{

	__raw_writel(val, &info->adc_base_spear6xx->ch_ctrl[n]);

}



static u32 spear_adc_get_average(struct spear_adc_info *info)

{

	if (of_device_is_compatible(info->np, "st,spear600-adc")) {

		return __raw_readl(&info->adc_base_spear6xx->average.msb) &

			DATA_MASK;

	} else {

		return __raw_readl(&info->adc_base_spear3xx->average) &

			DATA_MASK;

	}

}



static void spear_adc_set_scanrate(struct spear_adc_info *info, u32 rate)

{

	if (of_device_is_compatible(info->np, "st,spear600-adc")) {

		__raw_writel(SCAN_RATE_LO(rate),

			     &info->adc_base_spear6xx->scan_rate_lo);

		__raw_writel(SCAN_RATE_HI(rate),

			     &info->adc_base_spear6xx->scan_rate_hi);

	} else {

		__raw_writel(rate, &info->adc_base_spear3xx->scan_rate);

	}

}



static int spear_read_raw(struct iio_dev *indio_dev,

			  struct iio_chan_spec const *chan,

			  int *val,

			  int *val2,

			  long mask)

{

	struct spear_adc_info *info = iio_priv(indio_dev);

	u32 scale_mv;

	u32 status;



	switch (mask) {

	case 0:

		mutex_lock(&indio_dev->mlock);



		status = CHANNEL_NUM(chan->channel) |

			AVG_SAMPLE(info->avg_samples) |

			START_CONVERSION | ADC_ENABLE;

		if (info->vref_external == 0)

			status |= VREF_INTERNAL;



		spear_adc_set_status(info, status);

		wait_for_completion(&info->completion); /* set by ISR */

		*val = info->value;



		mutex_unlock(&indio_dev->mlock);



		return IIO_VAL_INT;



	case IIO_CHAN_INFO_SCALE:

		scale_mv = (info->vref_external * 1000) >> DATA_BITS;

		*val =  scale_mv / 1000;

		*val2 = (scale_mv % 1000) * 1000;

		return IIO_VAL_INT_PLUS_MICRO;

	}



	return -EINVAL;

}



#define SPEAR_ADC_CHAN(idx) {				\

	.type = IIO_VOLTAGE,				\

	.indexed = 1,					\

	.info_mask = IIO_CHAN_INFO_SCALE_SHARED_BIT,	\

	.channel = idx,					\

	.scan_type = {					\

		.sign = 'u',				\

		.storagebits = 16,			\

	},						\

}



static struct iio_chan_spec spear_adc_iio_channels[] = {

	SPEAR_ADC_CHAN(0),

	SPEAR_ADC_CHAN(1),

	SPEAR_ADC_CHAN(2),

	SPEAR_ADC_CHAN(3),

	SPEAR_ADC_CHAN(4),

	SPEAR_ADC_CHAN(5),

	SPEAR_ADC_CHAN(6),

	SPEAR_ADC_CHAN(7),

};



static irqreturn_t spear_adc_isr(int irq, void *dev_id)

{

	struct spear_adc_info *info = (struct spear_adc_info *)dev_id;



	/* Read value to clear IRQ */

	info->value = spear_adc_get_average(info);

	complete(&info->completion);



	return IRQ_HANDLED;

}



static int spear_adc_configure(struct spear_adc_info *info)

{

	int i;



	/* Reset ADC core */

	spear_adc_set_status(info, 0);

	__raw_writel(0, &info->adc_base_spear6xx->clk);

	for (i = 0; i < 8; i++)

		spear_adc_set_ctrl(info, i, 0);

	spear_adc_set_scanrate(info, 0);



	spear_adc_set_clk(info, info->sampling_freq);



	return 0;

}



static ssize_t spear_adc_read_frequency(struct device *dev,

					struct device_attribute *attr,

					char *buf)

{

	struct iio_dev *indio_dev = dev_get_drvdata(dev);

	struct spear_adc_info *info = iio_priv(indio_dev);



	return sprintf(buf, "%d\n", info->current_clk);

}



static ssize_t spear_adc_write_frequency(struct device *dev,

					 struct device_attribute *attr,

					 const char *buf,

					 size_t len)

{

	struct iio_dev *indio_dev = dev_get_drvdata(dev);

	struct spear_adc_info *info = iio_priv(indio_dev);

	u32 clk_high, clk_low, count;

	u32 apb_clk = clk_get_rate(info->clk);

	unsigned long lval;

	int ret;



	ret = kstrtoul(buf, 10, &lval);

	if (ret)

		return ret;



	mutex_lock(&indio_dev->mlock);



	if ((lval < CLK_MIN) || (lval > CLK_MAX)) {

		ret = -EINVAL;

		goto out;

	}



	count = (apb_clk + lval - 1) / lval;

	clk_low = count / 2;

	clk_high = count - clk_low;

	info->current_clk = apb_clk / count;

	spear_adc_set_clk(info, lval);



out:

	mutex_unlock(&indio_dev->mlock);



	return ret ? ret : len;

}



static IIO_DEV_ATTR_SAMP_FREQ(S_IWUSR | S_IRUGO,

			      spear_adc_read_frequency,

			      spear_adc_write_frequency);



static struct attribute *spear_attributes[] = {

	&iio_dev_attr_sampling_frequency.dev_attr.attr,

	NULL

};



static const struct attribute_group spear_attribute_group = {

	.attrs = spear_attributes,

};



static const struct iio_info spear_adc_iio_info = {

	.read_raw = &spear_read_raw,

	.attrs = &spear_attribute_group,

	.driver_module = THIS_MODULE,

};



static int __devinit spear_adc_probe(struct platform_device *pdev)

{

	struct device_node *np = pdev->dev.of_node;

	struct device *dev = &pdev->dev;

	struct spear_adc_info *info;

	struct iio_dev *iodev = NULL;

	int ret = -ENODEV;

	int irq;



	iodev = iio_allocate_device(sizeof(struct spear_adc_info));

	if (!iodev) {

		dev_err(dev, "failed allocating iio device\n");

		ret = -ENOMEM;

		goto errout1;

	}



	info = iio_priv(iodev);

	info->np = np;



	/*

	 * SPEAr600 has a different register layout than other SPEAr SoC's

	 * (e.g. SPEAr3xx). Let's provide two register base addresses

	 * to support multi-arch kernels.

	 */

	info->adc_base_spear6xx = of_iomap(np, 0);

	if (!info->adc_base_spear6xx) {

		dev_err(dev, "failed mapping memory\n");

		ret = -ENOMEM;

		goto errout2;

	}

	info->adc_base_spear3xx =

		(struct adc_regs_spear3xx *)info->adc_base_spear6xx;



	info->clk = clk_get(dev, NULL);

	if (IS_ERR(info->clk)) {

		dev_err(dev, "failed getting clock\n");

		goto errout3;

	}



	ret = clk_prepare(info->clk);

	if (ret) {

		dev_err(dev, "failed preparing clock\n");

		goto errout4;

	}



	ret = clk_enable(info->clk);

	if (ret) {

		dev_err(dev, "failed enabling clock\n");

		goto errout5;

	}



	irq = platform_get_irq(pdev, 0);

	if ((irq < 0) || (irq >= NR_IRQS)) {

		dev_err(dev, "failed getting interrupt resource\n");

		ret = -EINVAL;

		goto errout6;

	}



	ret = devm_request_irq(dev, irq, spear_adc_isr, 0, MOD_NAME, info);

	if (ret < 0) {

		dev_err(dev, "failed requesting interrupt\n");

		goto errout6;

	}



	if (of_property_read_u32(np, "sampling-frequency",

				 &info->sampling_freq)) {

		dev_err(dev, "sampling-frequency missing in DT\n");

		ret = -EINVAL;

		goto errout6;

	}



	/*

	 * Optional avg_samples defaults to 0, resulting in single data

	 * conversion

	 */

	of_property_read_u32(np, "average-samples", &info->avg_samples);



	/*

	 * Optional vref_external defaults to 0, resulting in internal vref

	 * selection

	 */

	of_property_read_u32(np, "vref-external", &info->vref_external);



	spear_adc_configure(info);



	platform_set_drvdata(pdev, iodev);



	init_completion(&info->completion);



	iodev->name = MOD_NAME;

	iodev->dev.parent = dev;

	iodev->info = &spear_adc_iio_info;

	iodev->modes = INDIO_DIRECT_MODE;

	iodev->channels = spear_adc_iio_channels;

	iodev->num_channels = ARRAY_SIZE(spear_adc_iio_channels);



	ret = iio_device_register(iodev);

	if (ret)

		goto errout6;



	dev_info(dev, "SPEAR ADC driver loaded, IRQ %d\n", irq);



	return 0;



errout6:

	clk_disable(info->clk);

errout5:

	clk_unprepare(info->clk);

errout4:

	clk_put(info->clk);

errout3:

	iounmap(info->adc_base_spear6xx);

errout2:

	iio_free_device(iodev);

errout1:

	return ret;

}



static int __devexit spear_adc_remove(struct platform_device *pdev)

{

	struct iio_dev *iodev = platform_get_drvdata(pdev);

	struct spear_adc_info *info = iio_priv(iodev);



	iio_device_unregister(iodev);

	platform_set_drvdata(pdev, NULL);

	clk_disable(info->clk);

	clk_unprepare(info->clk);

	clk_put(info->clk);

	iounmap(info->adc_base_spear6xx);

	iio_free_device(iodev);



	return 0;

}



static const struct of_device_id spear_adc_dt_ids[] = {

	{ .compatible = "st,spear600-adc", },

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(of, spear_adc_dt_ids);



static struct platform_driver spear_adc_driver = {

	.probe		= spear_adc_probe,

	.remove		= __devexit_p(spear_adc_remove),

	.driver		= {

		.name	= MOD_NAME,

		.owner	= THIS_MODULE,

		.of_match_table = of_match_ptr(spear_adc_dt_ids),

	},

};



module_platform_driver(spear_adc_driver);



MODULE_AUTHOR("Stefan Roese <sr@denx.de>");

MODULE_DESCRIPTION("SPEAr ADC driver");

MODULE_LICENSE("GPL");