Re: [PATCH] ARM: LPC32xx: ADC support

[Jonathan Cameron <jic23@cam.ac.uk>]

My comments are down near the iio bits.
> This patch adds a 3-channel ADC driver for the LPC32xx ARM SoC
>
> Signed-off-by: Roland Stigge<stigge@antcom.de>
>
> diff --git a/arch/arm/mach-lpc32xx/clock.c b/arch/arm/mach-lpc32xx/clock.c
> index c269ef5..9cda6fa 100644
> --- a/arch/arm/mach-lpc32xx/clock.c
> +++ b/arch/arm/mach-lpc32xx/clock.c
> @@ -760,6 +760,36 @@ static struct clk clk_tsc = {
>   	.get_rate	= local_return_parent_rate,
>   };
>
> +static int adc_onoff_enable(struct clk *clk, int enable)
> +{
> +	u32 tmp;
> +
> +	/* Use PERIPH_CLOCK */
> +	tmp = __raw_readl(LPC32XX_CLKPWR_ADC_CLK_CTRL_1);
> +	tmp |= LPC32XX_CLKPWR_ADCCTRL1_PCLK_SEL;
> +	/*
> +	 * Set clock divider so that we have equal to or less than
> +	 * 4.5MHz clock at ADC
> +	 */
> +	tmp |= clk->get_rate(clk) / 4500000 + 1;
> +	__raw_writel(tmp, LPC32XX_CLKPWR_ADC_CLK_CTRL_1);
> +
> +	if (enable == 0)
> +		__raw_writel(0, clk->enable_reg);
> +	else
> +		__raw_writel(clk->enable_mask, clk->enable_reg);
> +
> +	return 0;
> +}
> +
> +static struct clk clk_adc = {
> +	.parent		=&clk_pclk,
> +	.enable		= adc_onoff_enable,
> +	.enable_reg	= LPC32XX_CLKPWR_ADC_CLK_CTRL,
> +	.enable_mask	= LPC32XX_CLKPWR_ADC32CLKCTRL_CLK_EN,
> +	.get_rate	= local_return_parent_rate,
> +};
> +
>   static int mmc_onoff_enable(struct clk *clk, int enable)
>   {
>   	u32 tmp;
> @@ -1097,6 +1127,7 @@ static struct clk_lookup lookups[] = {
>   	_REGISTER_CLOCK("dev:ssp1", NULL, clk_ssp1)
>   	_REGISTER_CLOCK("lpc32xx_keys.0", NULL, clk_kscan)
>   	_REGISTER_CLOCK("lpc32xx-nand.0", "nand_ck", clk_nand)
> +	_REGISTER_CLOCK("lpc32xx-adc", NULL, clk_adc)
>   	_REGISTER_CLOCK(NULL, "i2s0_ck", clk_i2s0)
>   	_REGISTER_CLOCK(NULL, "i2s1_ck", clk_i2s1)
>   	_REGISTER_CLOCK("ts-lpc32xx", NULL, clk_tsc)
> diff --git a/arch/arm/mach-lpc32xx/common.c b/arch/arm/mach-lpc32xx/common.c
> index f220eb0..2f869c0 100644
> --- a/arch/arm/mach-lpc32xx/common.c
> +++ b/arch/arm/mach-lpc32xx/common.c
> @@ -137,6 +137,27 @@ struct platform_device lpc32xx_rtc_device = {
>   	.resource = lpc32xx_rtc_resources,
>   };
>
> +/*
> + * ADC support
> + */
> +static struct resource adc_resources[] = {
> +	{
> +		.start = LPC32XX_ADC_BASE,
> +		.end = LPC32XX_ADC_BASE + SZ_4K - 1,
> +		.flags = IORESOURCE_MEM,
> +	}, {
> +		.start = IRQ_LPC32XX_TS_IRQ,
> +		.end = IRQ_LPC32XX_TS_IRQ,
> +		.flags = IORESOURCE_IRQ,
> +	},
> +};
> +struct platform_device lpc32xx_adc_device = {
> +	.name =  "lpc32xx-adc",
> +	.id = -1,
> +	.num_resources = ARRAY_SIZE(adc_resources),
> +	.resource = adc_resources,
> +};
> +
>   #if defined(CONFIG_USB_OHCI_HCD)
>   /* The dmamask must be set for OHCI to work */
>   static u64 ohci_dmamask = ~(u32) 0;
> diff --git a/arch/arm/mach-lpc32xx/common.h b/arch/arm/mach-lpc32xx/common.h
> index e42d702..5bf0050 100644
> --- a/arch/arm/mach-lpc32xx/common.h
> +++ b/arch/arm/mach-lpc32xx/common.h
> @@ -30,6 +30,7 @@ extern struct platform_device lpc32xx_i2c0_device;
>   extern struct platform_device lpc32xx_i2c1_device;
>   extern struct platform_device lpc32xx_i2c2_device;
>   extern struct platform_device lpc32xx_tsc_device;
> +extern struct platform_device lpc32xx_adc_device;
>   extern struct platform_device lpc32xx_rtc_device;
>   extern struct platform_device lpc32xx_ohci_device;
>
> diff --git a/arch/arm/mach-lpc32xx/phy3250.c b/arch/arm/mach-lpc32xx/phy3250.c
> index 69a5ceb..23b484c 100644
> --- a/arch/arm/mach-lpc32xx/phy3250.c
> +++ b/arch/arm/mach-lpc32xx/phy3250.c
> @@ -317,6 +317,9 @@ static struct platform_device *phy3250_devs[] __initdata = {
>   #if defined(CONFIG_LPC_ENET)
>   	&lpc32xx_net_device,
>   #endif
> +#if defined(CONFIG_LPC32XX_ADC)
> +	&lpc32xx_adc_device,
> +#endif
>   };
>
>   static struct amba_device *amba_devs[] __initdata = {
> diff --git a/drivers/staging/iio/adc/Kconfig b/drivers/staging/iio/adc/Kconfig
> index d9decea..592eabd 100644
> --- a/drivers/staging/iio/adc/Kconfig
> +++ b/drivers/staging/iio/adc/Kconfig
> @@ -193,4 +193,13 @@ config MAX1363_RING_BUFFER
>   	  Say yes here to include ring buffer support in the MAX1363
>   	  ADC driver.
>
> +config LPC32XX_ADC
> +	tristate "NXP LPC32XX ADC"
> +	depends on ARCH_LPC32XX&&  !TOUCHSCREEN_LPC32XX
> +	help
> +	  Say yes here to build support for the integrated ADC inside the
> +	  LPC32XX SoC. Note that this feature uses the same hardware as the
> +	  touchscreen driver, so you can only select one of the two drivers
> +	  (lpc32xx_adc or lpc32xx_ts). Provides direct access via sysfs.
This should be a good base for messing around with the in kernel 
interfaces then ;)
> +
>   endmenu

A few structural changes needed, mainly to catch up with newer 
interfaces than used here, but
fundamentally sound.
> diff --git a/drivers/staging/iio/adc/Makefile b/drivers/staging/iio/adc/Makefile
> index ceee7f3..f83ab95 100644
> --- a/drivers/staging/iio/adc/Makefile
> +++ b/drivers/staging/iio/adc/Makefile
> @@ -37,3 +37,4 @@ obj-$(CONFIG_AD7192) += ad7192.o
>   obj-$(CONFIG_ADT7310) += adt7310.o
>   obj-$(CONFIG_ADT7410) += adt7410.o
>   obj-$(CONFIG_AD7280) += ad7280a.o
> +obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
> diff --git a/drivers/staging/iio/adc/lpc32xx_adc.c b/drivers/staging/iio/adc/lpc32xx_adc.c
> new file mode 100644
> index 0000000..6b27446
> --- /dev/null
> +++ b/drivers/staging/iio/adc/lpc32xx_adc.c
> @@ -0,0 +1,286 @@
> +/*
> + *  lpc32xx_adc.c - Support for ADC in LPC32XX
> + *
> + *  Copyright (C) 2011 Roland Stigge<stigge@antcom.de>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with this program; if not, write to the Free Software
> + *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +#include<linux/module.h>
> +#include<linux/platform_device.h>
> +#include<linux/interrupt.h>
> +#include<linux/device.h>
> +#include<linux/kernel.h>
> +#include<linux/slab.h>
> +#include<linux/io.h>
> +#include<linux/clk.h>
> +#include<linux/err.h>
> +#include<linux/completion.h>
> +
> +#include "../iio.h"
> +#include "../sysfs.h"
> +
> +/*
> + * LPC32XX registers definitions
> + */
> +
> +#define LPC32XX_ADC_SELECT(x)	((x) + 0x04)
> +#define LPC32XX_ADC_CTRL(x)	((x) + 0x08)
> +#define LPC32XX_ADC_VALUE(x)	((x) + 0x48)
> +
> +/* Bit definitions for LPC32XX_ADC_SELECT: */
> +#define AD_REFm         0x00000200 /* constant, always write this value! */
> +#define AD_REFp		0x00000080 /* constant, always write this value! */
> +#define AD_IN		0x00000010 /* multiple of this is the */
> +				   /* channel number: 0, 1, 2 */
> +#define AD_INTERNAL	0x00000004 /* constant, always write this value! */
> +
> +/* Bit definitions for LPC32XX_ADC_CTRL: */
> +#define AD_STROBE	0x00000002
> +#define AD_PDN_CTRL	0x00000004
> +
> +/* Bit definitions for LPC32XX_ADC_VALUE: */
> +#define ADC_VALUE_MASK	0x000003FF
> +
> +#define MOD_NAME "lpc32xx-adc"
> +
> +/*
> + * chip specifc information
> + */
> +
> +struct lpc32xx_adc_info {
> +	struct iio_dev *dev;
> +	void __iomem *adc_base;
irq is only used where the platform device is readily available so you could
drop it from this structure.

There is provision in iio via the iio_device_allocate parameter and iio_priv
to embed this structure within an iio_dev structure.  It makes for a 
cleaner code
but will require a trivial bit of reorganizing in your probe and remove
> +	int irq;
> +	struct clk *clk;
> +	struct completion completion;
> +
> +	u32 value;
> +};
> +
> +/*
> + * sysfs nodes
> + */
> +static ssize_t lpc32xx_adin_value(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)
> +{
> +	struct iio_dev *dev_info = dev_get_drvdata(dev);
> +	struct lpc32xx_adc_info *info = iio_priv(dev_info);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	int result;
> +
> +	mutex_lock(&dev_info->mlock);
> +	/* Measurement setup */
> +	__raw_writel(AD_INTERNAL | (AD_IN * this_attr->address) |
> +		AD_REFp | AD_REFm,
> +		LPC32XX_ADC_SELECT(info->adc_base));
> +	/* Trigger conversion */
> +	__raw_writel(AD_PDN_CTRL | AD_STROBE,
> +		LPC32XX_ADC_CTRL(info->adc_base));
> +
> +	wait_for_completion(&info->completion); /* set by ISR */
> +
> +	result = sprintf(buf, "%d\n", info->value);
> +
> +	mutex_unlock(&dev_info->mlock);
> +
> +	return result;
> +}
> +
> +static IIO_DEVICE_ATTR(in0_raw, S_IRUGO, lpc32xx_adin_value, NULL, 0);
> +static IIO_DEVICE_ATTR(in1_raw, S_IRUGO, lpc32xx_adin_value, NULL, 1);
> +static IIO_DEVICE_ATTR(in2_raw, S_IRUGO, lpc32xx_adin_value, NULL, 2);
> +
> +static struct attribute *lpc32xx_adin_attributes[] = {
> +	&iio_dev_attr_in0_raw.dev_attr.attr,
> +	&iio_dev_attr_in1_raw.dev_attr.attr,
> +	&iio_dev_attr_in2_raw.dev_attr.attr,
> +	NULL,
Please use iio_chan_info structures and the read_raw callback
rather than doing these attributes like this.  That will make for a much 
easier
job if anyone ever wants to use the inkernel interfaces (highly likely 
with a soc adc).


> +};
> +
> +static const struct attribute_group lpc32xx_adin_attribute_group = {
> +	.attrs = lpc32xx_adin_attributes,
> +};
> +
> +static const struct iio_info lpc32xx_adc_iio_info = {
> +	.attrs =&lpc32xx_adin_attribute_group,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static irqreturn_t lpc32xx_adc_isr(int irq, void *dev_id)
> +{
> +	struct lpc32xx_adc_info *info = (struct lpc32xx_adc_info *) dev_id;
> +
> +	/* Read value and clear irq */
> +	info->value = __raw_readl(LPC32XX_ADC_VALUE(info->adc_base))&
> +				ADC_VALUE_MASK;
> +	complete(&info->completion);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int __devinit lpc32xx_adc_probe(struct platform_device *pdev)
> +{
> +	struct lpc32xx_adc_info *info = NULL;
> +	struct resource *res;
> +	int retval = -ENODEV;
> +	struct iio_dev *iodev = NULL;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "failed to get platform I/O memory\n");
> +		retval = -EBUSY;
> +		goto errout1;
> +	}
> +
> +	iodev = iio_allocate_device(sizeof(struct lpc32xx_adc_info));
> +	if (!iodev) {
> +		dev_err(&pdev->dev, "failed allocating iio device\n");
> +		retval = -ENOMEM;
> +		goto errout1;
> +	}
> +
> +	info = iio_priv(iodev);
> +	info->dev = iodev;
> +
> +	info->adc_base = ioremap(res->start, res->end - res->start + 1);
> +	if (!info->adc_base) {
> +		dev_err(&pdev->dev, "failed mapping memory\n");
> +		retval = -EBUSY;
> +		goto errout3;
> +	}
> +
> +	iodev->name = MOD_NAME;
> +	iodev->dev.parent =&pdev->dev;
> +	iodev->info =&lpc32xx_adc_iio_info;
> +	iodev->modes = INDIO_DIRECT_MODE;
> +
> +	retval = iio_device_register(iodev);
> +	if (retval)
> +		goto errout4;
Generally we'd make the iio_device_register call only after everything 
else is set up as it is
at this point that the userspace interface becomes active.  Hence there 
might be a racecondition
if someone reads just after here.  I haven't checked thoroughly, but as 
a general rule, keeping
any interfaces from becoming available until everything else is done 
makes for easier to review
code if nothing else!
> +
> +	info->clk = clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(info->clk)) {
> +		dev_err(&pdev->dev, "failed getting clock\n");
> +		goto errout5;
> +	}
> +	clk_enable(info->clk);
> +
> +	info->irq = platform_get_irq(pdev, 0);
> +	if ((info->irq<  0) || (info->irq>= NR_IRQS)) {
> +		dev_err(&pdev->dev, "failed getting interrupt resource\n");
> +		retval = -EINVAL;
> +		goto errout6;
> +	}
> +
> +	retval = request_irq(info->irq, lpc32xx_adc_isr, 0, MOD_NAME, info);
> +	if (retval<  0) {
> +		dev_err(&pdev->dev, "failed requesting interrupt\n");
> +		goto errout6;
> +	}
> +
> +	platform_set_drvdata(pdev, info);
> +
> +	device_init_wakeup(&pdev->dev, 1);
> +	init_completion(&info->completion);
> +
> +	printk(KERN_INFO "LPC32XX ADC driver loaded, IRQ %d\n", info->irq);
> +
> +	return 0;
> +
> +errout6:
> +	clk_disable(info->clk);
> +	clk_put(info->clk);
> +errout5:
> +	iio_device_unregister(info->dev);
> +errout4:
> +	iounmap(info->adc_base);
> +errout3:
> +	iio_free_device(info->dev);
> +errout1:
> +	return retval;
> +}
> +
> +static int __devexit lpc32xx_adc_remove(struct platform_device *pdev)
> +{
> +	struct lpc32xx_adc_info *info = platform_get_drvdata(pdev);
> +
> +	free_irq(info->irq, info->dev);
> +	platform_set_drvdata(pdev, NULL);
> +	clk_disable(info->clk);
> +	clk_put(info->clk);
> +	iio_device_unregister(info->dev);
> +	iio_free_device(info->dev);
> +	iounmap(info->adc_base);
> +	kfree(info);
> +
> +	printk(KERN_INFO "LPC32XX ADC driver unloaded\n");
> +
> +	return 0;
> +}
> +
> +#if defined(CONFIG_SUSPEND)
> +static int lpc32xx_adc_suspend(struct device *dev)
> +{
> +	struct lpc32xx_adc_info *info = dev_get_drvdata(dev);
> +
> +	clk_disable(info->clk);
> +	return 0;
> +}
> +
> +static int lpc32xx_adc_resume(struct device *dev)
> +{
> +	struct lpc32xx_adc_info *info = dev_get_drvdata(dev);
> +
> +	clk_enable(info->clk);
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops lpc32xx_adc_pm_ops = {
> +	.suspend	= lpc32xx_adc_suspend,
> +	.resume		= lpc32xx_adc_resume,
> +};
> +#define LPC32XX_ADC_PM_OPS (&lpc32xx_adc_pm_ops)
> +#else
> +#define LPC32XX_ADC_PM_OPS NULL
> +#endif
> +
> +static struct platform_driver lpc32xx_adc_driver = {
> +	.probe		= lpc32xx_adc_probe,
> +	.remove		= __devexit_p(lpc32xx_adc_remove),
> +	.driver		= {
> +		.name	= MOD_NAME,
> +		.owner	= THIS_MODULE,
> +		.pm	= LPC32XX_ADC_PM_OPS,
> +	},
> +};
> +
> +static int __init lpc32xx_adc_init(void)
> +{
> +	return platform_driver_register(&lpc32xx_adc_driver);
> +}
> +
> +static void __exit lpc32xx_adc_exit(void)
> +{
> +	platform_driver_unregister(&lpc32xx_adc_driver);
> +}
> +
> +module_init(lpc32xx_adc_init);
> +module_exit(lpc32xx_adc_exit);
> +
> +MODULE_AUTHOR("Roland Stigge<stigge@antcom.de>");
> +MODULE_DESCRIPTION("LPC32XX ADC driver");
> +MODULE_LICENSE("GPL");