drivers/iio/adc/lpc18xx_adc.c

   1 /*
   2  * IIO ADC driver for NXP LPC18xx ADC
   3  *
   4  * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * UNSUPPORTED hardware features:
  11  *  - Hardware triggers
  12  *  - Burst mode
  13  *  - Interrupts
  14  *  - DMA
  15  */
  16
  17 #include <linux/clk.h>
  18 #include <linux/err.h>
  19 #include <linux/iio/iio.h>
  20 #include <linux/iio/driver.h>
  21 #include <linux/io.h>
  22 #include <linux/iopoll.h>
  23 #include <linux/module.h>
  24 #include <linux/mutex.h>
  25 #include <linux/of.h>
  26 #include <linux/of_device.h>
  27 #include <linux/platform_device.h>
  28 #include <linux/regulator/consumer.h>
  29
  30 /* LPC18XX ADC registers and bits */
  31 #define LPC18XX_ADC_CR                  0x000
  32 #define  LPC18XX_ADC_CR_CLKDIV_SHIFT    8
  33 #define  LPC18XX_ADC_CR_PDN             BIT(21)
  34 #define  LPC18XX_ADC_CR_START_NOW       (0x1 << 24)
  35 #define LPC18XX_ADC_GDR                 0x004
  36
  37 /* Data register bits */
  38 #define LPC18XX_ADC_SAMPLE_SHIFT        6
  39 #define LPC18XX_ADC_SAMPLE_MASK         0x3ff
  40 #define LPC18XX_ADC_CONV_DONE           BIT(31)
  41
  42 /* Clock should be 4.5 MHz or less */
  43 #define LPC18XX_ADC_CLK_TARGET          4500000
  44
  45 struct lpc18xx_adc {
  46         struct regulator *vref;
  47         void __iomem *base;
  48         struct device *dev;
  49         struct mutex lock;
  50         struct clk *clk;
  51         u32 cr_reg;
  52 };
  53
  54 #define LPC18XX_ADC_CHAN(_idx) {                                \
  55         .type = IIO_VOLTAGE,                                    \
  56         .indexed = 1,                                           \
  57         .channel = _idx,                                        \
  58         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
  59         .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
  60 }
  61
  62 static const struct iio_chan_spec lpc18xx_adc_iio_channels[] = {
  63         LPC18XX_ADC_CHAN(0),
  64         LPC18XX_ADC_CHAN(1),
  65         LPC18XX_ADC_CHAN(2),
  66         LPC18XX_ADC_CHAN(3),
  67         LPC18XX_ADC_CHAN(4),
  68         LPC18XX_ADC_CHAN(5),
  69         LPC18XX_ADC_CHAN(6),
  70         LPC18XX_ADC_CHAN(7),
  71 };
  72
  73 static int lpc18xx_adc_read_chan(struct lpc18xx_adc *adc, unsigned int ch)
  74 {
  75         int ret;
  76         u32 reg;
  77
  78         reg = adc->cr_reg | BIT(ch) | LPC18XX_ADC_CR_START_NOW;
  79         writel(reg, adc->base + LPC18XX_ADC_CR);
  80
  81         ret = readl_poll_timeout(adc->base + LPC18XX_ADC_GDR, reg,
  82                                  reg & LPC18XX_ADC_CONV_DONE, 3, 9);
  83         if (ret) {
  84                 dev_warn(adc->dev, "adc read timed out\n");
  85                 return ret;
  86         }
  87
  88         return (reg >> LPC18XX_ADC_SAMPLE_SHIFT) & LPC18XX_ADC_SAMPLE_MASK;
  89 }
  90
  91 static int lpc18xx_adc_read_raw(struct iio_dev *indio_dev,
  92                                 struct iio_chan_spec const *chan,
  93                                 int *val, int *val2, long mask)
  94 {
  95         struct lpc18xx_adc *adc = iio_priv(indio_dev);
  96
  97         switch (mask) {
  98         case IIO_CHAN_INFO_RAW:
  99                 mutex_lock(&adc->lock);
 100                 *val = lpc18xx_adc_read_chan(adc, chan->channel);
 101                 mutex_unlock(&adc->lock);
 102                 if (*val < 0)
 103                         return *val;
 104
 105                 return IIO_VAL_INT;
 106
 107         case IIO_CHAN_INFO_SCALE:
 108                 *val = regulator_get_voltage(adc->vref) / 1000;
 109                 *val2 = 10;
 110
 111                 return IIO_VAL_FRACTIONAL_LOG2;
 112         }
 113
 114         return -EINVAL;
 115 }
 116
 117 static const struct iio_info lpc18xx_adc_info = {
 118         .read_raw = lpc18xx_adc_read_raw,
 119         .driver_module = THIS_MODULE,
 120 };
 121
 122 static int lpc18xx_adc_probe(struct platform_device *pdev)
 123 {
 124         struct iio_dev *indio_dev;
 125         struct lpc18xx_adc *adc;
 126         struct resource *res;
 127         unsigned int clkdiv;
 128         unsigned long rate;
 129         int ret;
 130
 131         indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
 132         if (!indio_dev)
 133                 return -ENOMEM;
 134
 135         platform_set_drvdata(pdev, indio_dev);
 136         adc = iio_priv(indio_dev);
 137         adc->dev = &pdev->dev;
 138         mutex_init(&adc->lock);
 139
 140         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 141         adc->base = devm_ioremap_resource(&pdev->dev, res);
 142         if (IS_ERR(adc->base))
 143                 return PTR_ERR(adc->base);
 144
 145         adc->clk = devm_clk_get(&pdev->dev, NULL);
 146         if (IS_ERR(adc->clk)) {
 147                 dev_err(&pdev->dev, "error getting clock\n");
 148                 return PTR_ERR(adc->clk);
 149         }
 150
 151         rate = clk_get_rate(adc->clk);
 152         clkdiv = DIV_ROUND_UP(rate, LPC18XX_ADC_CLK_TARGET);
 153
 154         adc->vref = devm_regulator_get(&pdev->dev, "vref");
 155         if (IS_ERR(adc->vref)) {
 156                 dev_err(&pdev->dev, "error getting regulator\n");
 157                 return PTR_ERR(adc->vref);
 158         }
 159
 160         indio_dev->name = dev_name(&pdev->dev);
 161         indio_dev->dev.parent = &pdev->dev;
 162         indio_dev->info = &lpc18xx_adc_info;
 163         indio_dev->modes = INDIO_DIRECT_MODE;
 164         indio_dev->channels = lpc18xx_adc_iio_channels;
 165         indio_dev->num_channels = ARRAY_SIZE(lpc18xx_adc_iio_channels);
 166
 167         ret = regulator_enable(adc->vref);
 168         if (ret) {
 169                 dev_err(&pdev->dev, "unable to enable regulator\n");
 170                 return ret;
 171         }
 172
 173         ret = clk_prepare_enable(adc->clk);
 174         if (ret) {
 175                 dev_err(&pdev->dev, "unable to enable clock\n");
 176                 goto dis_reg;
 177         }
 178
 179         adc->cr_reg = (clkdiv << LPC18XX_ADC_CR_CLKDIV_SHIFT) |
 180                         LPC18XX_ADC_CR_PDN;
 181         writel(adc->cr_reg, adc->base + LPC18XX_ADC_CR);
 182
 183         ret = iio_device_register(indio_dev);
 184         if (ret) {
 185                 dev_err(&pdev->dev, "unable to register device\n");
 186                 goto dis_clk;
 187         }
 188
 189         return 0;
 190
 191 dis_clk:
 192         writel(0, adc->base + LPC18XX_ADC_CR);
 193         clk_disable_unprepare(adc->clk);
 194 dis_reg:
 195         regulator_disable(adc->vref);
 196         return ret;
 197 }
 198
 199 static int lpc18xx_adc_remove(struct platform_device *pdev)
 200 {
 201         struct iio_dev *indio_dev = platform_get_drvdata(pdev);
 202         struct lpc18xx_adc *adc = iio_priv(indio_dev);
 203
 204         iio_device_unregister(indio_dev);
 205
 206         writel(0, adc->base + LPC18XX_ADC_CR);
 207         clk_disable_unprepare(adc->clk);
 208         regulator_disable(adc->vref);
 209
 210         return 0;
 211 }
 212
 213 static const struct of_device_id lpc18xx_adc_match[] = {
 214         { .compatible = "nxp,lpc1850-adc" },
 215         { /* sentinel */ }
 216 };
 217 MODULE_DEVICE_TABLE(of, lpc18xx_adc_match);
 218
 219 static struct platform_driver lpc18xx_adc_driver = {
 220         .probe  = lpc18xx_adc_probe,
 221         .remove = lpc18xx_adc_remove,
 222         .driver = {
 223                 .name = "lpc18xx-adc",
 224                 .of_match_table = lpc18xx_adc_match,
 225         },
 226 };
 227 module_platform_driver(lpc18xx_adc_driver);
 228
 229 MODULE_DESCRIPTION("LPC18xx ADC driver");
 230 MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
 231 MODULE_LICENSE("GPL v2");