iio: adc: add NXP LPC18xx ADC driver
authorJoachim Eastwood <manabian@gmail.com>
Sat, 12 Mar 2016 12:30:14 +0000 (13:30 +0100)
committerJonathan Cameron <jic23@kernel.org>
Sat, 12 Mar 2016 18:11:48 +0000 (18:11 +0000)
Add base support for the 10-bit SAR ADC peripheral found
on NXP LPC18xx/43xx SoCs.

This is a minimal driver that does not support burst mode,
interrupts, DMA or hardware triggers.

User manual with register description can be found on:
LPC18xx: www.nxp.com/documents/user_manual/UM10430.pdf
LPC43xx: www.nxp.com/documents/user_manual/UM10503.pdf

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
drivers/iio/adc/Kconfig
drivers/iio/adc/Makefile
drivers/iio/adc/lpc18xx_adc.c [new file with mode: 0644]

index a8819a0..9ddcd5d 100644 (file)
@@ -235,6 +235,16 @@ config LP8788_ADC
          To compile this driver as a module, choose M here: the module will be
          called lp8788_adc.
 
+config LPC18XX_ADC
+       tristate "NXP LPC18xx ADC driver"
+       depends on ARCH_LPC18XX || COMPILE_TEST
+       depends on OF && HAS_IOMEM
+       help
+         Say yes here to build support for NXP LPC18XX ADC.
+
+         To compile this driver as a module, choose M here: the module will be
+         called lpc18xx_adc.
+
 config MAX1027
        tristate "Maxim max1027 ADC driver"
        depends on SPI
index b1aa456..1a4ac45 100644 (file)
@@ -24,6 +24,7 @@ obj-$(CONFIG_HI8435) += hi8435.o
 obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
 obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
 obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
+obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
diff --git a/drivers/iio/adc/lpc18xx_adc.c b/drivers/iio/adc/lpc18xx_adc.c
new file mode 100644 (file)
index 0000000..3ef18f4
--- /dev/null
@@ -0,0 +1,231 @@
+/*
+ * IIO ADC driver for NXP LPC18xx ADC
+ *
+ * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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,
+       .driver_module = THIS_MODULE,
+};
+
+static int lpc18xx_adc_probe(struct platform_device *pdev)
+{
+       struct iio_dev *indio_dev;
+       struct lpc18xx_adc *adc;
+       struct resource *res;
+       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);
+
+       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       adc->base = devm_ioremap_resource(&pdev->dev, res);
+       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->dev.parent = &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");