drivers/iio/adc/ep93xx_adc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Driver for ADC module on the Cirrus Logic EP93xx series of SoCs
  *
  * Copyright (C) 2015 Alexander Sverdlin
  *
  * The driver uses polling to get the conversion status. According to EP93xx
  * datasheets, reading ADCResult register starts the conversion, but user is also
  * responsible for ensuring that delay between adjacent conversion triggers is
  * long enough so that maximum allowed conversion rate is not exceeded. This
  * basically renders IRQ mode unusable.
  */

 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/iio/iio.h>
 #include <linux/io.h>
 #include <linux/irqflags.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/platform_device.h>

 /*
  * This code could benefit from real HR Timers, but jiffy granularity would
  * lower ADC conversion rate down to CONFIG_HZ, so we fallback to busy wait
  * in such case.
  *
  * HR Timers-based version loads CPU only up to 10% during back to back ADC
  * conversion, while busy wait-based version consumes whole CPU power.
  */
 #ifdef CONFIG_HIGH_RES_TIMERS
 #define ep93xx_adc_delay(usmin, usmax) usleep_range(usmin, usmax)
 #else
 #define ep93xx_adc_delay(usmin, usmax) udelay(usmin)
 #endif

 #define EP93XX_ADC_RESULT	0x08
 #define   EP93XX_ADC_SDR	BIT(31)
 #define EP93XX_ADC_SWITCH	0x18
 #define EP93XX_ADC_SW_LOCK	0x20

 struct ep93xx_adc_priv {
 	struct clk *clk;
 	void __iomem *base;
 	int lastch;
 	struct mutex lock;
 };

 #define EP93XX_ADC_CH(index, dname, swcfg) {			\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
 	.channel = index,					\
 	.address = swcfg,					\
 	.datasheet_name = dname,				\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) |	\
 				   BIT(IIO_CHAN_INFO_OFFSET),	\
 }

 /*
  * Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets.
  * EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is
  * not defined. So the last three are numbered randomly, let's say.
  */
 static const struct iio_chan_spec ep93xx_adc_channels[8] = {
 	EP93XX_ADC_CH(0, "YM",	0x608),
 	EP93XX_ADC_CH(1, "SXP",	0x680),
 	EP93XX_ADC_CH(2, "SXM",	0x640),
 	EP93XX_ADC_CH(3, "SYP",	0x620),
 	EP93XX_ADC_CH(4, "SYM",	0x610),
 	EP93XX_ADC_CH(5, "XP",	0x601),
 	EP93XX_ADC_CH(6, "XM",	0x602),
 	EP93XX_ADC_CH(7, "YP",	0x604),
 };

 static int ep93xx_read_raw(struct iio_dev *iiodev,
 			   struct iio_chan_spec const *channel, int *value,
 			   int *shift, long mask)
 {
 	struct ep93xx_adc_priv *priv = iio_priv(iiodev);
 	unsigned long timeout;
 	int ret;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&priv->lock);
 		if (priv->lastch != channel->channel) {
 			priv->lastch = channel->channel;
 			/*
 			 * Switch register is software-locked, unlocking must be
 			 * immediately followed by write
 			 */
 			local_irq_disable();
 			writel_relaxed(0xAA, priv->base + EP93XX_ADC_SW_LOCK);
 			writel_relaxed(channel->address,
 				       priv->base + EP93XX_ADC_SWITCH);
 			local_irq_enable();
 			/*
 			 * Settling delay depends on module clock and could be
 			 * 2ms or 500us
 			 */
 			ep93xx_adc_delay(2000, 2000);
 		}
 		/* Start the conversion, eventually discarding old result */
 		readl_relaxed(priv->base + EP93XX_ADC_RESULT);
 		/* Ensure maximum conversion rate is not exceeded */
 		ep93xx_adc_delay(DIV_ROUND_UP(1000000, 925),
 				 DIV_ROUND_UP(1000000, 925));
 		/* At this point conversion must be completed, but anyway... */
 		ret = IIO_VAL_INT;
 		timeout = jiffies + msecs_to_jiffies(1) + 1;
 		while (1) {
 			u32 t;

 			t = readl_relaxed(priv->base + EP93XX_ADC_RESULT);
 			if (t & EP93XX_ADC_SDR) {
 				*value = sign_extend32(t, 15);
 				break;
 			}

 			if (time_after(jiffies, timeout)) {
 				dev_err(&iiodev->dev, "Conversion timeout\n");
 				ret = -ETIMEDOUT;
 				break;
 			}

 			cpu_relax();
 		}
 		mutex_unlock(&priv->lock);
 		return ret;

 	case IIO_CHAN_INFO_OFFSET:
 		/* According to datasheet, range is -25000..25000 */
 		*value = 25000;
 		return IIO_VAL_INT;

 	case IIO_CHAN_INFO_SCALE:
 		/* Typical supply voltage is 3.3v */
 		*value = (1ULL << 32) * 3300 / 50000;
 		*shift = 32;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}

 	return -EINVAL;
 }

 static const struct iio_info ep93xx_adc_info = {
 	.read_raw = ep93xx_read_raw,
 };

 static int ep93xx_adc_probe(struct platform_device *pdev)
 {
 	int ret;
 	struct iio_dev *iiodev;
 	struct ep93xx_adc_priv *priv;
 	struct clk *pclk;

 	iiodev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
 	if (!iiodev)
 		return -ENOMEM;
 	priv = iio_priv(iiodev);

 	priv->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);

 	iiodev->name = dev_name(&pdev->dev);
 	iiodev->modes = INDIO_DIRECT_MODE;
 	iiodev->info = &ep93xx_adc_info;
 	iiodev->num_channels = ARRAY_SIZE(ep93xx_adc_channels);
 	iiodev->channels = ep93xx_adc_channels;

 	priv->lastch = -1;
 	mutex_init(&priv->lock);

 	platform_set_drvdata(pdev, iiodev);

 	priv->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(priv->clk)) {
 		dev_err(&pdev->dev, "Cannot obtain clock\n");
 		return PTR_ERR(priv->clk);
 	}

 	pclk = clk_get_parent(priv->clk);
 	if (!pclk) {
 		dev_warn(&pdev->dev, "Cannot obtain parent clock\n");
 	} else {
 		/*
 		 * This is actually a place for improvement:
 		 * EP93xx ADC supports two clock divisors -- 4 and 16,
 		 * resulting in conversion rates 3750 and 925 samples per second
 		 * with 500us or 2ms settling time respectively.
 		 * One might find this interesting enough to be configurable.
 		 */
 		ret = clk_set_rate(priv->clk, clk_get_rate(pclk) / 16);
 		if (ret)
 			dev_warn(&pdev->dev, "Cannot set clock rate\n");
 		/*
 		 * We can tolerate rate setting failure because the module should
 		 * work in any case.
 		 */
 	}

 	ret = clk_prepare_enable(priv->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "Cannot enable clock\n");
 		return ret;
 	}

 	ret = iio_device_register(iiodev);
 	if (ret)
 		clk_disable_unprepare(priv->clk);

 	return ret;
 }

 static int ep93xx_adc_remove(struct platform_device *pdev)
 {
 	struct iio_dev *iiodev = platform_get_drvdata(pdev);
 	struct ep93xx_adc_priv *priv = iio_priv(iiodev);

 	iio_device_unregister(iiodev);
 	clk_disable_unprepare(priv->clk);

 	return 0;
 }

 static struct platform_driver ep93xx_adc_driver = {
 	.driver = {
 		.name = "ep93xx-adc",
 	},
 	.probe = ep93xx_adc_probe,
 	.remove = ep93xx_adc_remove,
 };
 module_platform_driver(ep93xx_adc_driver);

 MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>");
 MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:ep93xx-adc");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Driver for ADC module on the Cirrus Logic EP93xx series of SoCs
	*
	* Copyright (C) 2015 Alexander Sverdlin
	*
	* The driver uses polling to get the conversion status. According to EP93xx
	* datasheets, reading ADCResult register starts the conversion, but user is also
	* responsible for ensuring that delay between adjacent conversion triggers is
	* long enough so that maximum allowed conversion rate is not exceeded. This
	* basically renders IRQ mode unusable.
	*/

	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/device.h>
	#include <linux/err.h>
	#include <linux/iio/iio.h>
	#include <linux/io.h>
	#include <linux/irqflags.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/platform_device.h>

	/*
	* This code could benefit from real HR Timers, but jiffy granularity would
	* lower ADC conversion rate down to CONFIG_HZ, so we fallback to busy wait
	* in such case.
	*
	* HR Timers-based version loads CPU only up to 10% during back to back ADC
	* conversion, while busy wait-based version consumes whole CPU power.
	*/
	#ifdef CONFIG_HIGH_RES_TIMERS
	#define ep93xx_adc_delay(usmin, usmax) usleep_range(usmin, usmax)
	#else
	#define ep93xx_adc_delay(usmin, usmax) udelay(usmin)
	#endif

	#define EP93XX_ADC_RESULT 0x08
	#define EP93XX_ADC_SDR BIT(31)
	#define EP93XX_ADC_SWITCH 0x18
	#define EP93XX_ADC_SW_LOCK 0x20

	struct ep93xx_adc_priv {
	struct clk *clk;
	void __iomem *base;
	int lastch;
	struct mutex lock;
	};

	#define EP93XX_ADC_CH(index, dname, swcfg) { \
	.type = IIO_VOLTAGE, \
	.indexed = 1, \
	.channel = index, \
	.address = swcfg, \
	.datasheet_name = dname, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) \| \
	BIT(IIO_CHAN_INFO_OFFSET), \
	}

	/*
	* Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets.
	* EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is
	* not defined. So the last three are numbered randomly, let's say.
	*/
	static const struct iio_chan_spec ep93xx_adc_channels[8] = {
	EP93XX_ADC_CH(0, "YM", 0x608),
	EP93XX_ADC_CH(1, "SXP", 0x680),
	EP93XX_ADC_CH(2, "SXM", 0x640),
	EP93XX_ADC_CH(3, "SYP", 0x620),
	EP93XX_ADC_CH(4, "SYM", 0x610),
	EP93XX_ADC_CH(5, "XP", 0x601),
	EP93XX_ADC_CH(6, "XM", 0x602),
	EP93XX_ADC_CH(7, "YP", 0x604),
	};

	static int ep93xx_read_raw(struct iio_dev *iiodev,
	struct iio_chan_spec const channel, int value,
	int *shift, long mask)
	{
	struct ep93xx_adc_priv *priv = iio_priv(iiodev);
	unsigned long timeout;
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	mutex_lock(&priv->lock);
	if (priv->lastch != channel->channel) {
	priv->lastch = channel->channel;
	/*
	* Switch register is software-locked, unlocking must be
	* immediately followed by write
	*/
	local_irq_disable();
	writel_relaxed(0xAA, priv->base + EP93XX_ADC_SW_LOCK);
	writel_relaxed(channel->address,
	priv->base + EP93XX_ADC_SWITCH);
	local_irq_enable();
	/*
	* Settling delay depends on module clock and could be
	* 2ms or 500us
	*/
	ep93xx_adc_delay(2000, 2000);
	}
	/* Start the conversion, eventually discarding old result */
	readl_relaxed(priv->base + EP93XX_ADC_RESULT);
	/* Ensure maximum conversion rate is not exceeded */
	ep93xx_adc_delay(DIV_ROUND_UP(1000000, 925),
	DIV_ROUND_UP(1000000, 925));
	/* At this point conversion must be completed, but anyway... */
	ret = IIO_VAL_INT;
	timeout = jiffies + msecs_to_jiffies(1) + 1;
	while (1) {
	u32 t;

	t = readl_relaxed(priv->base + EP93XX_ADC_RESULT);
	if (t & EP93XX_ADC_SDR) {
	*value = sign_extend32(t, 15);
	break;
	}

	if (time_after(jiffies, timeout)) {
	dev_err(&iiodev->dev, "Conversion timeout\n");
	ret = -ETIMEDOUT;
	break;
	}

	cpu_relax();
	}
	mutex_unlock(&priv->lock);
	return ret;

	case IIO_CHAN_INFO_OFFSET:
	/* According to datasheet, range is -25000..25000 */
	*value = 25000;
	return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
	/* Typical supply voltage is 3.3v */
	value = (1ULL << 32) 3300 / 50000;
	*shift = 32;
	return IIO_VAL_FRACTIONAL_LOG2;
	}

	return -EINVAL;
	}

	static const struct iio_info ep93xx_adc_info = {
	.read_raw = ep93xx_read_raw,
	};

	static int ep93xx_adc_probe(struct platform_device *pdev)
	{
	int ret;
	struct iio_dev *iiodev;
	struct ep93xx_adc_priv *priv;
	struct clk *pclk;

	iiodev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
	if (!iiodev)
	return -ENOMEM;
	priv = iio_priv(iiodev);

	priv->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->base))
	return PTR_ERR(priv->base);

	iiodev->name = dev_name(&pdev->dev);
	iiodev->modes = INDIO_DIRECT_MODE;
	iiodev->info = &ep93xx_adc_info;
	iiodev->num_channels = ARRAY_SIZE(ep93xx_adc_channels);
	iiodev->channels = ep93xx_adc_channels;

	priv->lastch = -1;
	mutex_init(&priv->lock);

	platform_set_drvdata(pdev, iiodev);

	priv->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(priv->clk)) {
	dev_err(&pdev->dev, "Cannot obtain clock\n");
	return PTR_ERR(priv->clk);
	}

	pclk = clk_get_parent(priv->clk);
	if (!pclk) {
	dev_warn(&pdev->dev, "Cannot obtain parent clock\n");
	} else {
	/*
	* This is actually a place for improvement:
	* EP93xx ADC supports two clock divisors -- 4 and 16,
	* resulting in conversion rates 3750 and 925 samples per second
	* with 500us or 2ms settling time respectively.
	* One might find this interesting enough to be configurable.
	*/
	ret = clk_set_rate(priv->clk, clk_get_rate(pclk) / 16);
	if (ret)
	dev_warn(&pdev->dev, "Cannot set clock rate\n");
	/*
	* We can tolerate rate setting failure because the module should
	* work in any case.
	*/
	}

	ret = clk_prepare_enable(priv->clk);
	if (ret) {
	dev_err(&pdev->dev, "Cannot enable clock\n");
	return ret;
	}

	ret = iio_device_register(iiodev);
	if (ret)
	clk_disable_unprepare(priv->clk);

	return ret;
	}

	static int ep93xx_adc_remove(struct platform_device *pdev)
	{
	struct iio_dev *iiodev = platform_get_drvdata(pdev);
	struct ep93xx_adc_priv *priv = iio_priv(iiodev);

	iio_device_unregister(iiodev);
	clk_disable_unprepare(priv->clk);

	return 0;
	}

	static struct platform_driver ep93xx_adc_driver = {
	.driver = {
	.name = "ep93xx-adc",
	},
	.probe = ep93xx_adc_probe,
	.remove = ep93xx_adc_remove,
	};
	module_platform_driver(ep93xx_adc_driver);

	MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>");
	MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:ep93xx-adc");