text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * IIO ADC driver for NXP LPC18xx ADC
   *
   * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
   *
   * UNSUPPORTED hardware features:
   *  - Hardware triggers
   *  - Burst mode
   *  - Interrupts
   *  - DMA
   */
  
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/iio/iio.h>
  #include <linux/iio/driver.h>
  #include <linux/io.h>
  #include <linux/iopoll.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <linux/platform_device.h>
  #include <linux/regulator/consumer.h>
  
  /* LPC18XX ADC registers and bits */
  #define LPC18XX_ADC_CR			0x000
  #define  LPC18XX_ADC_CR_CLKDIV_SHIFT	8
  #define  LPC18XX_ADC_CR_PDN		BIT(21)
  #define  LPC18XX_ADC_CR_START_NOW	(0x1 << 24)
  #define LPC18XX_ADC_GDR			0x004
  
  /* Data register bits */
  #define LPC18XX_ADC_SAMPLE_SHIFT	6
  #define LPC18XX_ADC_SAMPLE_MASK		0x3ff
  #define LPC18XX_ADC_CONV_DONE		BIT(31)
  
  /* Clock should be 4.5 MHz or less */
  #define LPC18XX_ADC_CLK_TARGET		4500000
  
  struct lpc18xx_adc {
  	struct regulator *vref;
  	void __iomem *base;
  	struct device *dev;
  	struct mutex lock;
  	struct clk *clk;
  	u32 cr_reg;
  };
  
  #define LPC18XX_ADC_CHAN(_idx) {				\
  	.type = IIO_VOLTAGE,					\
  	.indexed = 1,						\
  	.channel = _idx,					\
  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
  }
  
  static const struct iio_chan_spec lpc18xx_adc_iio_channels[] = {
  	LPC18XX_ADC_CHAN(0),
  	LPC18XX_ADC_CHAN(1),
  	LPC18XX_ADC_CHAN(2),
  	LPC18XX_ADC_CHAN(3),
  	LPC18XX_ADC_CHAN(4),
  	LPC18XX_ADC_CHAN(5),
  	LPC18XX_ADC_CHAN(6),
  	LPC18XX_ADC_CHAN(7),
  };
  
  static int lpc18xx_adc_read_chan(struct lpc18xx_adc *adc, unsigned int ch)
  {
  	int ret;
  	u32 reg;
  
  	reg = adc->cr_reg | BIT(ch) | LPC18XX_ADC_CR_START_NOW;
  	writel(reg, adc->base + LPC18XX_ADC_CR);
  
  	ret = readl_poll_timeout(adc->base + LPC18XX_ADC_GDR, reg,
  				 reg & LPC18XX_ADC_CONV_DONE, 3, 9);
  	if (ret) {
  		dev_warn(adc->dev, "adc read timed out\n");
  		return ret;
  	}
  
  	return (reg >> LPC18XX_ADC_SAMPLE_SHIFT) & LPC18XX_ADC_SAMPLE_MASK;
  }
  
  static int lpc18xx_adc_read_raw(struct iio_dev *indio_dev,
  				struct iio_chan_spec const *chan,
  				int *val, int *val2, long mask)
  {
  	struct lpc18xx_adc *adc = iio_priv(indio_dev);
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		mutex_lock(&adc->lock);
  		*val = lpc18xx_adc_read_chan(adc, chan->channel);
  		mutex_unlock(&adc->lock);
  		if (*val < 0)
  			return *val;
  
  		return IIO_VAL_INT;
  
  	case IIO_CHAN_INFO_SCALE:
  		*val = regulator_get_voltage(adc->vref) / 1000;
  		*val2 = 10;
  
  		return IIO_VAL_FRACTIONAL_LOG2;
  	}
  
  	return -EINVAL;
  }
  
  static const struct iio_info lpc18xx_adc_info = {
  	.read_raw = lpc18xx_adc_read_raw,
  };
  
  static int lpc18xx_adc_probe(struct platform_device *pdev)
  {
  	struct iio_dev *indio_dev;
  	struct lpc18xx_adc *adc;
  	unsigned int clkdiv;
  	unsigned long rate;
  	int ret;
  
  	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
  	if (!indio_dev)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, indio_dev);
  	adc = iio_priv(indio_dev);
  	adc->dev = &pdev->dev;
  	mutex_init(&adc->lock);
  
  	adc->base = devm_platform_ioremap_resource(pdev, 0);
  	if (IS_ERR(adc->base))
  		return PTR_ERR(adc->base);
  
  	adc->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(adc->clk)) {
  		dev_err(&pdev->dev, "error getting clock\n");
  		return PTR_ERR(adc->clk);
  	}
  
  	rate = clk_get_rate(adc->clk);
  	clkdiv = DIV_ROUND_UP(rate, LPC18XX_ADC_CLK_TARGET);
  
  	adc->vref = devm_regulator_get(&pdev->dev, "vref");
  	if (IS_ERR(adc->vref)) {
  		dev_err(&pdev->dev, "error getting regulator\n");
  		return PTR_ERR(adc->vref);
  	}
  
  	indio_dev->name = dev_name(&pdev->dev);
  	indio_dev->info = &lpc18xx_adc_info;
  	indio_dev->modes = INDIO_DIRECT_MODE;
  	indio_dev->channels = lpc18xx_adc_iio_channels;
  	indio_dev->num_channels = ARRAY_SIZE(lpc18xx_adc_iio_channels);
  
  	ret = regulator_enable(adc->vref);
  	if (ret) {
  		dev_err(&pdev->dev, "unable to enable regulator\n");
  		return ret;
  	}
  
  	ret = clk_prepare_enable(adc->clk);
  	if (ret) {
  		dev_err(&pdev->dev, "unable to enable clock\n");
  		goto dis_reg;
  	}
  
  	adc->cr_reg = (clkdiv << LPC18XX_ADC_CR_CLKDIV_SHIFT) |
  			LPC18XX_ADC_CR_PDN;
  	writel(adc->cr_reg, adc->base + LPC18XX_ADC_CR);
  
  	ret = iio_device_register(indio_dev);
  	if (ret) {
  		dev_err(&pdev->dev, "unable to register device\n");
  		goto dis_clk;
  	}
  
  	return 0;
  
  dis_clk:
  	writel(0, adc->base + LPC18XX_ADC_CR);
  	clk_disable_unprepare(adc->clk);
  dis_reg:
  	regulator_disable(adc->vref);
  	return ret;
  }
  
  static int lpc18xx_adc_remove(struct platform_device *pdev)
  {
  	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
  	struct lpc18xx_adc *adc = iio_priv(indio_dev);
  
  	iio_device_unregister(indio_dev);
  
  	writel(0, adc->base + LPC18XX_ADC_CR);
  	clk_disable_unprepare(adc->clk);
  	regulator_disable(adc->vref);
  
  	return 0;
  }
  
  static const struct of_device_id lpc18xx_adc_match[] = {
  	{ .compatible = "nxp,lpc1850-adc" },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, lpc18xx_adc_match);
  
  static struct platform_driver lpc18xx_adc_driver = {
  	.probe	= lpc18xx_adc_probe,
  	.remove	= lpc18xx_adc_remove,
  	.driver	= {
  		.name = "lpc18xx-adc",
  		.of_match_table = lpc18xx_adc_match,
  	},
  };
  module_platform_driver(lpc18xx_adc_driver);
  
  MODULE_DESCRIPTION("LPC18xx ADC driver");
  MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
  MODULE_LICENSE("GPL v2");
  