Re: [PATCH v3 1/4] iio: adc: add NXP LPC18xx ADC driver

[Jonathan Cameron <jic23@kernel.org>]

On 12/03/16 12:30, Joachim Eastwood wrote:
> 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>
Applied to the togreg branch of iio.git - initially pushed out as
testing for the autobuilders to play with it.

Thanks,

Jonathan
> ---
>  drivers/iio/adc/Kconfig       |  10 ++
>  drivers/iio/adc/Makefile      |   1 +
>  drivers/iio/adc/lpc18xx_adc.c | 231 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 242 insertions(+)
>  create mode 100644 drivers/iio/adc/lpc18xx_adc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index a8819a08a828..9ddcd5db039b 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -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
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index b1aa456e6af3..1a4ac4590857 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -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
> index 000000000000..3ef18f4b27f0
> --- /dev/null
> +++ b/drivers/iio/adc/lpc18xx_adc.c
> @@ -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");
>