Re: [PATCH v4 1/3] iio: imx8qxp-adc: Add binding documentation for NXP IMX8QXP ADC

[Jonathan Cameron]

On Sun, 12 Sep 2021 15:13:32 +0800
Cai Huoqing <caihuoqing@xxxxxxxxx> wrote:

Patch title seems to be wrong..  Was fine in v3.

> The NXP i.MX 8QuadXPlus SOC a new ADC IP, so add
> binding documentation for NXP IMX8QXP ADC
> 
> Signed-off-by: Cai Huoqing <caihuoqing@xxxxxxxxx>

Hi. I'd missed some potential issues around runtime pm in previous
reviews. Sorry about that.  Unfortunately rereading code often throws
up problems that were missed on earlier reading.

Jonathan


> ---
> v1->v2:	*Squash patches 1, 2, 3, and 5 into a single patch.
> 	*Add device specific prefix.
> 	*Remove the brackets around individual numbers.
> 	*Make use of FIELD_PREP() and FIELD_GET().
> 	*Remove a lot of cache values.
> 	*Replace mlock with adc->lock.
> 	*Move adc->value read from isr to the completion.
> 	*Set pm_runtime_disable/_put_noidle() before adc_disable.
> 	*Add error handler-err_disable_reg/err_unprepare_clk.
> v2->v3:	*Add "return 0" to adc_runtime_resume().
> v3->v4:	*Sort header file declarations in alphabetical order.
> 	*Remove explicitly cast from "void *".
> 	*Make use of dev_err_probe().
> 	*Add some blank lines to help readability.
> 
> v1 link:
> https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210830172140.414-4-caihuoqing@xxxxxxxxx/
> v3 link:
> https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210907015724.1377-2-caihuoqing@xxxxxxxxx/
> 
>  drivers/iio/adc/Kconfig       |  10 +
>  drivers/iio/adc/Makefile      |   1 +
>  drivers/iio/adc/imx8qxp-adc.c | 461 ++++++++++++++++++++++++++++++++++
>  3 files changed, 472 insertions(+)
>  create mode 100644 drivers/iio/adc/imx8qxp-adc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index af168e1c9fdb..fa8ad63d6ac2 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -530,6 +530,16 @@ config IMX7D_ADC
>  	  This driver can also be built as a module. If so, the module will be
>  	  called imx7d_adc.
>  
> +config IMX8QXP_ADC
> +	tristate "NXP IMX8QXP ADC driver"
> +	depends on ARCH_MXC_ARM64 || COMPILE_TEST
> +	depends on HAS_IOMEM
> +	help
> +	  Say yes here to build support for IMX8QXP ADC.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called imx8qxp-adc.
> +
>  config LP8788_ADC
>  	tristate "LP8788 ADC driver"
>  	depends on MFD_LP8788
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d68550f493e3..d3f53549720c 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -46,6 +46,7 @@ obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
>  obj-$(CONFIG_HI8435) += hi8435.o
>  obj-$(CONFIG_HX711) += hx711.o
>  obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
> +obj-$(CONFIG_IMX8QXP_ADC) += imx8qxp-adc.o
>  obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
>  obj-$(CONFIG_INGENIC_ADC) += ingenic-adc.o
>  obj-$(CONFIG_INTEL_MRFLD_ADC) += intel_mrfld_adc.o
> diff --git a/drivers/iio/adc/imx8qxp-adc.c b/drivers/iio/adc/imx8qxp-adc.c
> new file mode 100644
> index 000000000000..e48cf31b2e4c
> --- /dev/null
> +++ b/drivers/iio/adc/imx8qxp-adc.c
> @@ -0,0 +1,461 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * NXP i.MX8QXP ADC driver
> + *
> + * Based on the work of Haibo Chen <haibo.chen@xxxxxxx>
> + * The initial developer of the original code is Haibo Chen.
> + * Portions created by Haibo Chen are Copyright (C) 2018 NXP.
> + * All Rights Reserved.
> + *
> + * Copyright (C) 2018 NXP
> + * Copyright (C) 2021 Cai Huoqing
> + */
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/clk.h>
> +#include <linux/completion.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <linux/iio/driver.h>

Not used.  That header only includes the map interfaces used
to provide services to other drivers in kernel.  This driver is not
yet doing that (and might well do it via dt anwyay which doesn't need
that header)

> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>

I don't think the driver is using this one either.  That only tends
to get used when handling non standard ABI.  This driver is all standard
stuff which is great.

> +
> +#define ADC_DRIVER_NAME		"imx8qxp-adc"
> +
> +/* Register map definition */
> +#define IMX8QXP_ADR_ADC_CTRL		0x10
> +#define IMX8QXP_ADR_ADC_STAT		0x14
> +#define IMX8QXP_ADR_ADC_IE		0x18
> +#define IMX8QXP_ADR_ADC_DE		0x1c
> +#define IMX8QXP_ADR_ADC_CFG		0x20
> +#define IMX8QXP_ADR_ADC_FCTRL		0x30
> +#define IMX8QXP_ADR_ADC_SWTRIG		0x34
> +#define IMX8QXP_ADR_ADC_TCTRL(tid)	(0xc0 + tid * 4)
> +#define IMX8QXP_ADR_ADC_CMDH(cid)	(0x100 + cid * 8)
> +#define IMX8QXP_ADR_ADC_CMDL(cid)	(0x104 + cid * 8)
> +#define IMX8QXP_ADR_ADC_RESFIFO		0x300
> +#define IMX8QXP_ADR_ADC_TST		0xffc
> +
> +/* ADC bit shift */
> +#define IMX8QXP_ADC_IE_FWMIE_MASK		GENMASK(1, 0)
> +#define IMX8QXP_ADC_CTRL_FIFO_RESET_MASK	BIT(8)
> +#define IMX8QXP_ADC_CTRL_SOFTWARE_RESET_MASK	BIT(1)
> +#define IMX8QXP_ADC_CTRL_ADC_EN_MASK		BIT(0)
> +#define IMX8QXP_ADC_TCTRL_TCMD_MASK		GENMASK(31, 24)
> +#define IMX8QXP_ADC_TCTRL_TDLY_MASK		GENMASK(23, 16)
> +#define IMX8QXP_ADC_TCTRL_TPRI_MASK		GENMASK(15, 8)
> +#define IMX8QXP_ADC_TCTRL_HTEN_MASK		GENMASK(7, 0)
> +#define IMX8QXP_ADC_CMDL_CSCALE_MASK		GENMASK(13, 8)
> +#define IMX8QXP_ADC_CMDL_MODE_MASK		BIT(7)
> +#define IMX8QXP_ADC_CMDL_DIFF_MASK		BIT(6)
> +#define IMX8QXP_ADC_CMDL_ABSEL_MASK		BIT(5)
> +#define IMX8QXP_ADC_CMDL_ADCH_MASK		GENMASK(2, 0)
> +#define IMX8QXP_ADC_CMDH_NEXT_MASK		GENMASK(31, 24)
> +#define IMX8QXP_ADC_CMDH_LOOP_MASK		GENMASK(23, 16)
> +#define IMX8QXP_ADC_CMDH_AVGS_MASK		GENMASK(15, 12)
> +#define IMX8QXP_ADC_CMDH_STS_MASK		BIT(8)
> +#define IMX8QXP_ADC_CMDH_LWI_MASK		GENMASK(7, 7)
> +#define IMX8QXP_ADC_CMDH_CMPEN_MASK		GENMASK(0, 0)
> +#define IMX8QXP_ADC_CFG_PWREN_MASK		BIT(28)
> +#define IMX8QXP_ADC_CFG_PUDLY_MASK		GENMASK(23, 16)
> +#define IMX8QXP_ADC_CFG_REFSEL_MASK		GENMASK(7, 6)
> +#define IMX8QXP_ADC_CFG_PWRSEL_MASK		GENMASK(5, 4)
> +#define IMX8QXP_ADC_CFG_TPRICTRL_MASK		GENMASK(3, 0)
> +#define IMX8QXP_ADC_FCTRL_FWMARK_MASK		GENMASK(20, 16)
> +#define IMX8QXP_ADC_FCTRL_FCOUNT_MASK		GENMASK(4, 0)
> +#define IMX8QXP_ADC_RESFIFO_VAL_MASK		GENMASK(18, 3)
> +
> +/* ADC PARAMETER*/
> +#define IMX8QXP_ADC_CMDL_CHANNEL_SCALE_FULL		GENMASK(5, 0)
> +#define IMX8QXP_ADC_CMDL_SEL_A_A_B_CHANNEL		0
> +#define IMX8QXP_ADC_CMDL_STANDARD_RESOLUTION		0
> +#define IMX8QXP_ADC_CMDL_MODE_SINGLE			0
> +#define IMX8QXP_ADC_CMDH_LWI_INCREMENT_DIS		0
> +#define IMX8QXP_ADC_CMDH_CMPEN_DIS			0
> +#define IMX8QXP_ADC_PAUSE_EN				BIT(31)
> +#define IMX8QXP_ADC_TCTRL_TPRI_PRIORITY_HIGH		0
> +
> +#define IMX8QXP_ADC_TCTRL_HTEN_HW_TIRG_DIS		0
> +
> +#define IMX8QXP_ADC_TIMEOUT		msecs_to_jiffies(100)
> +
> +struct imx8qxp_adc {
> +	struct device *dev;
> +	void __iomem *regs;
> +	struct clk *clk;
> +	struct clk *ipg_clk;
> +	struct regulator *vref;
> +	struct mutex lock;
> +	struct completion completion;
> +};
> +
> +#define IMX8QXP_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) |	\
> +				BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
> +}
> +
> +static const struct iio_chan_spec imx8qxp_adc_iio_channels[] = {
> +	IMX8QXP_ADC_CHAN(0),
> +	IMX8QXP_ADC_CHAN(1),
> +	IMX8QXP_ADC_CHAN(2),
> +	IMX8QXP_ADC_CHAN(3),
> +	IMX8QXP_ADC_CHAN(4),
> +	IMX8QXP_ADC_CHAN(5),
> +	IMX8QXP_ADC_CHAN(6),
> +	IMX8QXP_ADC_CHAN(7),
> +};
> +
> +static void imx8qxp_adc_reset(struct imx8qxp_adc *adc)
> +{
> +	u32 ctrl;
> +
> +	/*software reset, need to clear the set bit*/
> +	ctrl = readl(adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +	ctrl |= FIELD_PREP(IMX8QXP_ADC_CTRL_SOFTWARE_RESET_MASK, 1);
> +	writel(ctrl, adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +	udelay(10);
> +	ctrl &= ~FIELD_PREP(IMX8QXP_ADC_CTRL_SOFTWARE_RESET_MASK, 1);
> +	writel(ctrl, adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +
> +	/* reset the fifo */
> +	ctrl |= FIELD_PREP(IMX8QXP_ADC_CTRL_FIFO_RESET_MASK, 1);
> +	writel(ctrl, adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +}
> +
> +static void imx8qxp_adc_reg_config(struct imx8qxp_adc *adc, int channel)
> +{
> +	u32 adc_cfg, adc_tctrl, adc_cmdl, adc_cmdh;
> +
> +	/* ADC configuration */
> +	adc_cfg = FIELD_PREP(IMX8QXP_ADC_CFG_PWREN_MASK, 1) |
> +		  FIELD_PREP(IMX8QXP_ADC_CFG_PUDLY_MASK, 0x80)|
> +		  FIELD_PREP(IMX8QXP_ADC_CFG_REFSEL_MASK, 0) |
> +		  FIELD_PREP(IMX8QXP_ADC_CFG_PWRSEL_MASK, 3) |
> +		  FIELD_PREP(IMX8QXP_ADC_CFG_TPRICTRL_MASK, 0);
> +	writel(adc_cfg, adc->regs + IMX8QXP_ADR_ADC_CFG);
> +
> +	/* config the trigger control */
> +	adc_tctrl = FIELD_PREP(IMX8QXP_ADC_TCTRL_TCMD_MASK, 1) |
> +		    FIELD_PREP(IMX8QXP_ADC_TCTRL_TDLY_MASK, 0) |
> +		    FIELD_PREP(IMX8QXP_ADC_TCTRL_TPRI_MASK, IMX8QXP_ADC_TCTRL_TPRI_PRIORITY_HIGH) |
> +		    FIELD_PREP(IMX8QXP_ADC_TCTRL_HTEN_MASK, IMX8QXP_ADC_TCTRL_HTEN_HW_TIRG_DIS);
> +	writel(adc_cfg, adc->regs + IMX8QXP_ADR_ADC_TCTRL(0));
> +
> +	/* config the cmd */
> +	adc_cmdl = FIELD_PREP(IMX8QXP_ADC_CMDL_CSCALE_MASK, IMX8QXP_ADC_CMDL_CHANNEL_SCALE_FULL) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDL_MODE_MASK, IMX8QXP_ADC_CMDL_STANDARD_RESOLUTION) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDL_DIFF_MASK, IMX8QXP_ADC_CMDL_MODE_SINGLE) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDL_ABSEL_MASK, IMX8QXP_ADC_CMDL_SEL_A_A_B_CHANNEL) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDL_ADCH_MASK, channel);
> +	writel(adc_cmdl, adc->regs + IMX8QXP_ADR_ADC_CMDL(0));
> +
> +	adc_cmdh = FIELD_PREP(IMX8QXP_ADC_CMDH_NEXT_MASK, 0) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDH_LOOP_MASK, 0) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDH_AVGS_MASK, 7) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDH_STS_MASK, 0) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDH_LWI_MASK, IMX8QXP_ADC_CMDH_LWI_INCREMENT_DIS) |
> +		   FIELD_PREP(IMX8QXP_ADC_CMDH_CMPEN_MASK, IMX8QXP_ADC_CMDH_CMPEN_DIS);
> +	writel(adc_cmdh, adc->regs + IMX8QXP_ADR_ADC_CMDH(0));
> +}
> +
> +static void imx8qxp_adc_fifo_config(struct imx8qxp_adc *adc)
> +{
> +	u32 fifo_ctrl, interrupt_en;
> +
> +	fifo_ctrl = readl(adc->regs + IMX8QXP_ADR_ADC_FCTRL);
> +	fifo_ctrl &= ~IMX8QXP_ADC_FCTRL_FWMARK_MASK;
> +	/* set the watermark level to 1 */
> +	fifo_ctrl |= FIELD_PREP(IMX8QXP_ADC_FCTRL_FWMARK_MASK, 0);
> +	writel(fifo_ctrl, adc->regs + IMX8QXP_ADR_ADC_FCTRL);
> +
> +	/* FIFO Watermark Interrupt Enable */
> +	interrupt_en = readl(adc->regs + IMX8QXP_ADR_ADC_IE);
> +	interrupt_en |= FIELD_PREP(IMX8QXP_ADC_IE_FWMIE_MASK, 1);
> +	writel(interrupt_en, adc->regs + IMX8QXP_ADR_ADC_IE);
> +}
> +
> +static void imx8qxp_adc_disable(struct imx8qxp_adc *adc)
> +{
> +	u32 ctrl;
> +
> +	ctrl = readl(adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +	ctrl &= ~FIELD_PREP(IMX8QXP_ADC_CTRL_ADC_EN_MASK, 1);
> +	writel(ctrl, adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +}
> +
> +static int imx8qxp_adc_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,

Trivial but please wrap this at a shorter line length.  Whilst we allow up to 100 characters
when it helps readability, in cases where it doesn't make any difference <= 80 chars is
preferred.

Some of the other long lines are more readable because they aren't broken (like the
FIELD_PREP() above, but this one is not.

> +				int *val, int *val2, long mask)
> +{
> +	struct imx8qxp_adc *adc = iio_priv(indio_dev);
> +	struct device *dev = adc->dev;
> +
> +	u32 ctrl, vref_uv;
> +	long ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		pm_runtime_get_sync(dev);
> +
> +		mutex_lock(&adc->lock);
> +		reinit_completion(&adc->completion);
> +
> +		imx8qxp_adc_reg_config(adc, chan->channel);
> +
> +		imx8qxp_adc_fifo_config(adc);
> +
> +		/* adc enable */
> +		ctrl = readl(adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +		ctrl |= FIELD_PREP(IMX8QXP_ADC_CTRL_ADC_EN_MASK, 1);
> +		writel(ctrl, adc->regs + IMX8QXP_ADR_ADC_CTRL);
> +		/* adc start */
> +		writel(1, adc->regs + IMX8QXP_ADR_ADC_SWTRIG);
> +
> +		ret = wait_for_completion_interruptible_timeout(&adc->completion,
> +								IMX8QXP_ADC_TIMEOUT);
> +
> +		pm_runtime_mark_last_busy(dev);
> +		pm_runtime_put_sync_autosuspend(dev);
> +
> +		if (ret == 0) {
> +			mutex_unlock(&adc->lock);
> +			return -ETIMEDOUT;
> +		}
> +		if (ret < 0) {
> +			mutex_unlock(&adc->lock);
> +			return ret;
> +		}
> +
> +		*val = FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
> +				 readl(adc->regs + IMX8QXP_ADR_ADC_RESFIFO));
> +
> +		mutex_unlock(&adc->lock);
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		vref_uv = regulator_get_voltage(adc->vref);
> +		*val = vref_uv / 1000;
> +		*val2 = 12;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val = clk_get_rate(adc->clk) / 3;
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static irqreturn_t imx8qxp_adc_isr(int irq, void *dev_id)
> +{
> +	struct imx8qxp_adc *adc = dev_id;
> +
> +	u32 fifo_count;
> +
> +	fifo_count = FIELD_GET(IMX8QXP_ADC_FCTRL_FCOUNT_MASK,
> +			       readl(adc->regs + IMX8QXP_ADR_ADC_FCTRL));
> +
> +	if (fifo_count)
> +		complete(&adc->completion);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int imx8qxp_adc_reg_access(struct iio_dev *indio_dev, unsigned int reg,
> +				  unsigned int writeval, unsigned int *readval)
> +{
> +	struct imx8qxp_adc *adc = iio_priv(indio_dev);
> +	struct device *dev = adc->dev;
> +
> +	if (!readval || reg % 4 || reg > IMX8QXP_ADR_ADC_TST)
> +		return -EINVAL;
> +
> +	pm_runtime_get_sync(dev);
> +
> +	*readval = readl(adc->regs + reg);
> +
> +	pm_runtime_mark_last_busy(dev);
> +	pm_runtime_put_sync_autosuspend(dev);
> +
> +	return 0;
> +}
> +
> +static const struct iio_info imx8qxp_adc_iio_info = {
> +	.read_raw = &imx8qxp_adc_read_raw,
> +	.debugfs_reg_access = &imx8qxp_adc_reg_access,
> +};
> +
> +static int imx8qxp_adc_probe(struct platform_device *pdev)
> +{
> +	struct imx8qxp_adc *adc;
> +	struct iio_dev *indio_dev;
> +	struct device *dev = &pdev->dev;
> +	int irq;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
> +	if (!indio_dev) {
> +		dev_err(dev, "Failed allocating iio device\n");
> +		return -ENOMEM;
> +	}
> +
> +	adc = iio_priv(indio_dev);
> +	adc->dev = dev;
> +
> +	mutex_init(&adc->lock);
> +	adc->regs = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(adc->regs))
> +		return PTR_ERR(adc->regs);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	adc->clk = devm_clk_get(dev, "per");
> +	if (IS_ERR(adc->clk))
> +		return dev_err_probe(dev, PTR_ERR(adc->clk), "Failed getting clock\n");
> +
> +	adc->ipg_clk = devm_clk_get(dev, "ipg");
> +	if (IS_ERR(adc->ipg_clk))
> +		return dev_err_probe(dev, PTR_ERR(adc->ipg_clk), "Failed getting clock\n");
> +
> +	adc->vref = devm_regulator_get(dev, "vref");
> +	if (IS_ERR(adc->vref))
> +		return dev_err_probe(dev, PTR_ERR(adc->vref), "Failed getting reference voltage\n");
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	init_completion(&adc->completion);
> +
> +	indio_dev->name = dev_name(dev);
> +	indio_dev->info = &imx8qxp_adc_iio_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = imx8qxp_adc_iio_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(imx8qxp_adc_iio_channels);
> +
> +	ret = devm_request_irq(dev, irq, imx8qxp_adc_isr, 0, dev_name(dev), adc);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Failed requesting irq, irq = %d\n", irq);
> +
> +	imx8qxp_adc_reset(adc);
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret) {
> +		imx8qxp_adc_disable(adc);
> +		return dev_err_probe(dev, ret, "Couldn't register the device.\n");
> +	}
> +
> +	pm_runtime_set_active(dev);

Normally you do this with a device which is active (here that means regulators and
clocks enabled which isn't done in this probe).

Then autosuspend will power everything down again for you leaving us in a nice consistent
state.  If runtime pm isn't enabled on the system, then it will do nothing and the
device will work fine (subject to using lots of unnecessary power).

Note we probably have other examples where this is done wrong in IIO.
I am part way through a general check on runtime pm and know there is plenty more
to do.

> +	pm_runtime_set_autosuspend_delay(dev, 50);
> +	pm_runtime_use_autosuspend(dev);
> +	pm_runtime_enable(dev);
> +
> +	return 0;
> +}
> +
> +static int imx8qxp_adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +	struct imx8qxp_adc *adc = iio_priv(indio_dev);
> +	struct device *dev = adc->dev;
> +
> +	pm_runtime_get_sync(dev);

This turns on the regulator which is fine.. But who turns it off again?
Same for the clocks.

> +
> +	iio_device_unregister(indio_dev);
> +
> +	pm_runtime_disable(dev);
> +	pm_runtime_put_noidle(dev);

This just reduces the reference counter, it doesn't call runtime suspend.
The particular pattern you use here is normally done so that we can manually
disable everything in a system that doesn't support runtime PM. 

Which also raises a potential problem for the clocks and regulators.
If runtime PM isn't compiled into the kernel they will never be turned on.

The usual pattern to avoid that is to turn them on manually in probe()
then enable runtime pm to turn them off again.  If runtime pm isn't
compiled in then everything is just left on.

> +
> +	imx8qxp_adc_disable(adc);
> +
> +	return 0;
> +}
> +
> +static int imx8qxp_adc_runtime_suspend(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +	struct imx8qxp_adc *adc = iio_priv(indio_dev);
> +
> +	imx8qxp_adc_disable(adc);
> +
> +	clk_disable_unprepare(adc->clk);
> +	clk_disable_unprepare(adc->ipg_clk);
> +	regulator_disable(adc->vref);
> +
> +	return 0;
> +}
> +
> +static int imx8qxp_adc_runtime_resume(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +	struct imx8qxp_adc *adc = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = regulator_enable(adc->vref);
> +	if (ret) {
> +		dev_err(dev, "Can't enable adc reference top voltage, err = %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(adc->clk);
> +	if (ret) {
> +		dev_err(dev, "Could not prepare or enable clock.\n");
> +		goto err_disable_reg;
> +	}
> +
> +	ret = clk_prepare_enable(adc->ipg_clk);
> +	if (ret) {
> +		dev_err(dev, "Could not prepare or enable clock.\n");
> +		goto err_unprepare_clk;
> +	}
> +
> +	imx8qxp_adc_reset(adc);
> +
> +	return 0;
> +
> +err_unprepare_clk:
> +	clk_disable_unprepare(adc->clk);
> +
> +err_disable_reg:
> +	regulator_disable(adc->vref);
> +
> +	return ret;
> +}
> +
> +static const struct dev_pm_ops imx8qxp_adc_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> +	SET_RUNTIME_PM_OPS(imx8qxp_adc_runtime_suspend, imx8qxp_adc_runtime_resume, NULL)
> +};
> +
> +static const struct of_device_id imx8qxp_adc_match[] = {
> +	{ .compatible = "nxp,imx8qxp-adc", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, imx8qxp_adc_match);
> +
> +static struct platform_driver imx8qxp_adc_driver = {
> +	.probe		= imx8qxp_adc_probe,
> +	.remove		= imx8qxp_adc_remove,
> +	.driver		= {
> +		.name	= ADC_DRIVER_NAME,
> +		.of_match_table = imx8qxp_adc_match,
> +		.pm	= &imx8qxp_adc_pm_ops,
> +	},
> +};
> +
> +module_platform_driver(imx8qxp_adc_driver);
> +
> +MODULE_DESCRIPTION("i.MX8QuadXPlus ADC driver");
> +MODULE_LICENSE("GPL v2");