iio: dac: add NXP LPC18xx DAC driver

Add base support for the 10-bit DAC peripheral found
on NXP LPC18xx/43xx SoCs.

This is a minimal driver that does not support DMA or
interrupts.

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>

3 files changed, 221 insertions, 0 deletions

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index a995139f907c..210db81ca144 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -154,6 +154,16 @@ config AD7303
           To compile this driver as module choose M here: the module will be called
           ad7303.
 
+config LPC18XX_DAC
+        tristate "NXP LPC18xx DAC driver"
+        depends on ARCH_LPC18XX || COMPILE_TEST
+        depends on OF && HAS_IOMEM
+        help
+          Say yes here to build support for NXP LPC18XX DAC.
+
+          To compile this driver as a module, choose M here: the module will be
+          called lpc18xx_dac.
+
 config M62332
         tristate "Mitsubishi M62332 DAC driver"
         depends on I2C
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 67b48429686d..420a15cdaa53 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_AD5764) += ad5764.o
 obj-$(CONFIG_AD5791) += ad5791.o
 obj-$(CONFIG_AD5686) += ad5686.o
 obj-$(CONFIG_AD7303) += ad7303.o
+obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
 obj-$(CONFIG_M62332) += m62332.o
 obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
diff --git a/drivers/iio/dac/lpc18xx_dac.c b/drivers/iio/dac/lpc18xx_dac.c
new file mode 100644
index 000000000000..55d1456a059d
--- /dev/null
+++ b/drivers/iio/dac/lpc18xx_dac.c
@@ -0,0 +1,210 @@
+/*
+ * IIO DAC driver for NXP LPC18xx DAC
+ *
+ * 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:
+ *  - 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 DAC registers and bits */
+#define LPC18XX_DAC_CR                  0x000
+#define  LPC18XX_DAC_CR_VALUE_SHIFT     6
+#define  LPC18XX_DAC_CR_VALUE_MASK      0x3ff
+#define  LPC18XX_DAC_CR_BIAS            BIT(16)
+#define LPC18XX_DAC_CTRL                0x004
+#define  LPC18XX_DAC_CTRL_DMA_ENA       BIT(3)
+
+struct lpc18xx_dac {
+        struct regulator *vref;
+        void __iomem *base;
+        struct mutex lock;
+        struct clk *clk;
+};
+
+static const struct iio_chan_spec lpc18xx_dac_iio_channels[] = {
+        {
+                .type = IIO_VOLTAGE,
+                .output = 1,
+                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+                                      BIT(IIO_CHAN_INFO_SCALE),
+        },
+};
+
+static int lpc18xx_dac_read_raw(struct iio_dev *indio_dev,
+                                struct iio_chan_spec const *chan,
+                                int *val, int *val2, long mask)
+{
+        struct lpc18xx_dac *dac = iio_priv(indio_dev);
+        u32 reg;
+
+        switch (mask) {
+        case IIO_CHAN_INFO_RAW:
+                reg = readl(dac->base + LPC18XX_DAC_CR);
+                *val = reg >> LPC18XX_DAC_CR_VALUE_SHIFT;
+                *val &= LPC18XX_DAC_CR_VALUE_MASK;
+
+                return IIO_VAL_INT;
+
+        case IIO_CHAN_INFO_SCALE:
+                *val = regulator_get_voltage(dac->vref) / 1000;
+                *val2 = 10;
+
+                return IIO_VAL_FRACTIONAL_LOG2;
+        }
+
+        return -EINVAL;
+}
+
+static int lpc18xx_dac_write_raw(struct iio_dev *indio_dev,
+                                 struct iio_chan_spec const *chan,
+                                 int val, int val2, long mask)
+{
+        struct lpc18xx_dac *dac = iio_priv(indio_dev);
+        u32 reg;
+
+        switch (mask) {
+        case IIO_CHAN_INFO_RAW:
+                if (val < 0 || val > LPC18XX_DAC_CR_VALUE_MASK)
+                        return -EINVAL;
+
+                reg = LPC18XX_DAC_CR_BIAS;
+                reg |= val << LPC18XX_DAC_CR_VALUE_SHIFT;
+
+                mutex_lock(&dac->lock);
+                writel(reg, dac->base + LPC18XX_DAC_CR);
+                writel(LPC18XX_DAC_CTRL_DMA_ENA, dac->base + LPC18XX_DAC_CTRL);
+                mutex_unlock(&dac->lock);
+
+                return 0;
+        }
+
+        return -EINVAL;
+}
+
+static const struct iio_info lpc18xx_dac_info = {
+        .read_raw = lpc18xx_dac_read_raw,
+        .write_raw = lpc18xx_dac_write_raw,
+        .driver_module = THIS_MODULE,
+};
+
+static int lpc18xx_dac_probe(struct platform_device *pdev)
+{
+        struct iio_dev *indio_dev;
+        struct lpc18xx_dac *dac;
+        struct resource *res;
+        int ret;
+
+        indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*dac));
+        if (!indio_dev)
+                return -ENOMEM;
+
+        platform_set_drvdata(pdev, indio_dev);
+        dac = iio_priv(indio_dev);
+        mutex_init(&dac->lock);
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        dac->base = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(dac->base))
+                return PTR_ERR(dac->base);
+
+        dac->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(dac->clk)) {
+                dev_err(&pdev->dev, "error getting clock\n");
+                return PTR_ERR(dac->clk);
+        }
+
+        dac->vref = devm_regulator_get(&pdev->dev, "vref");
+        if (IS_ERR(dac->vref)) {
+                dev_err(&pdev->dev, "error getting regulator\n");
+                return PTR_ERR(dac->vref);
+        }
+
+        indio_dev->name = dev_name(&pdev->dev);
+        indio_dev->dev.parent = &pdev->dev;
+        indio_dev->info = &lpc18xx_dac_info;
+        indio_dev->modes = INDIO_DIRECT_MODE;
+        indio_dev->channels = lpc18xx_dac_iio_channels;
+        indio_dev->num_channels = ARRAY_SIZE(lpc18xx_dac_iio_channels);
+
+        ret = regulator_enable(dac->vref);
+        if (ret) {
+                dev_err(&pdev->dev, "unable to enable regulator\n");
+                return ret;
+        }
+
+        ret = clk_prepare_enable(dac->clk);
+        if (ret) {
+                dev_err(&pdev->dev, "unable to enable clock\n");
+                goto dis_reg;
+        }
+
+        writel(0, dac->base + LPC18XX_DAC_CTRL);
+        writel(0, dac->base + LPC18XX_DAC_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:
+        clk_disable_unprepare(dac->clk);
+dis_reg:
+        regulator_disable(dac->vref);
+        return ret;
+}
+
+static int lpc18xx_dac_remove(struct platform_device *pdev)
+{
+        struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+        struct lpc18xx_dac *dac = iio_priv(indio_dev);
+
+        iio_device_unregister(indio_dev);
+
+        writel(0, dac->base + LPC18XX_DAC_CTRL);
+        clk_disable_unprepare(dac->clk);
+        regulator_disable(dac->vref);
+
+        return 0;
+}
+
+static const struct of_device_id lpc18xx_dac_match[] = {
+        { .compatible = "nxp,lpc1850-dac" },
+        { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, lpc18xx_dac_match);
+
+static struct platform_driver lpc18xx_dac_driver = {
+        .probe  = lpc18xx_dac_probe,
+        .remove = lpc18xx_dac_remove,
+        .driver = {
+                .name = "lpc18xx-dac",
+                .of_match_table = lpc18xx_dac_match,
+        },
+};
+module_platform_driver(lpc18xx_dac_driver);
+
+MODULE_DESCRIPTION("LPC18xx DAC driver");
+MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
+MODULE_LICENSE("GPL v2");