drivers/iio/adc/nxp-sar-adc.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * NXP SAR-ADC driver (adapted from Freescale Vybrid vf610 ADC driver
 * by Fugang Duan <B38611@freescale.com>)
 *
 * Copyright 2013 Freescale Semiconductor, Inc.
 * Copyright 2017, 2020-2025 NXP
 * Copyright 2025, Linaro Ltd
 */
#include <linux/bitfield.h>
#include <linux/bitops.h>
#include <linux/circ_buf.h>
#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/iopoll.h>
#include <linux/math64.h>
#include <linux/minmax.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/time.h>
#include <linux/types.h>
#include <linux/units.h>

#include <linux/iio/iio.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>

/* SAR ADC registers. */
#define NXP_SAR_ADC_CDR(__base, __channel)	(((__base) + 0x100) + ((__channel) * 0x4))

#define NXP_SAR_ADC_CDR_CDATA_MASK	GENMASK(11, 0)
#define NXP_SAR_ADC_CDR_VALID		BIT(19)

/* Main Configuration Register */
#define NXP_SAR_ADC_MCR(__base)		((__base) + 0x00)

#define NXP_SAR_ADC_MCR_PWDN		BIT(0)
#define NXP_SAR_ADC_MCR_ACKO		BIT(5)
#define NXP_SAR_ADC_MCR_ADCLKSEL	BIT(8)
#define NXP_SAR_ADC_MCR_TSAMP_MASK	GENMASK(10, 9)
#define NXP_SAR_ADC_MCR_NRSMPL_MASK	GENMASK(12, 11)
#define NXP_SAR_ADC_MCR_AVGEN		BIT(13)
#define NXP_SAR_ADC_MCR_CALSTART	BIT(14)
#define NXP_SAR_ADC_MCR_NSTART		BIT(24)
#define NXP_SAR_ADC_MCR_MODE		BIT(29)
#define NXP_SAR_ADC_MCR_OWREN		BIT(31)

/* Main Status Register */
#define NXP_SAR_ADC_MSR(__base)		((__base) + 0x04)

#define NXP_SAR_ADC_MSR_CALBUSY		BIT(29)
#define NXP_SAR_ADC_MSR_CALFAIL		BIT(30)

/* Interrupt Status Register */
#define NXP_SAR_ADC_ISR(__base)		((__base) + 0x10)

#define NXP_SAR_ADC_ISR_ECH		BIT(0)

/*  Channel Pending Register */
#define NXP_SAR_ADC_CEOCFR0(__base)	((__base) + 0x14)
#define NXP_SAR_ADC_CEOCFR1(__base)	((__base) + 0x18)

#define NXP_SAR_ADC_EOC_CH(c)		BIT(c)

/* Interrupt Mask Register */
#define NXP_SAR_ADC_IMR(__base)		((__base) + 0x20)

/* Channel Interrupt Mask Register */
#define NXP_SAR_ADC_CIMR0(__base)	((__base) + 0x24)
#define NXP_SAR_ADC_CIMR1(__base)	((__base) + 0x28)

/* DMA Setting Register */
#define NXP_SAR_ADC_DMAE(__base)	((__base) + 0x40)

#define NXP_SAR_ADC_DMAE_DMAEN		BIT(0)
#define NXP_SAR_ADC_DMAE_DCLR		BIT(1)

/* DMA Control register */
#define NXP_SAR_ADC_DMAR0(__base)	((__base) + 0x44)
#define NXP_SAR_ADC_DMAR1(__base)	((__base) + 0x48)

/* Conversion Timing Register */
#define NXP_SAR_ADC_CTR0(__base)	((__base) + 0x94)
#define NXP_SAR_ADC_CTR1(__base)	((__base) + 0x98)

#define NXP_SAR_ADC_CTR_INPSAMP_MIN	0x08
#define NXP_SAR_ADC_CTR_INPSAMP_MAX	0xff

/* Normal Conversion Mask Register */
#define NXP_SAR_ADC_NCMR0(__base)	((__base) + 0xa4)
#define NXP_SAR_ADC_NCMR1(__base)	((__base) + 0xa8)

/* Normal Conversion Mask Register field define */
#define NXP_SAR_ADC_CH_MASK		GENMASK(7, 0)

/* Other field define */
#define NXP_SAR_ADC_CONV_TIMEOUT	(msecs_to_jiffies(100))
#define NXP_SAR_ADC_CAL_TIMEOUT_US	(100 * USEC_PER_MSEC)
#define NXP_SAR_ADC_WAIT_US		(2 * USEC_PER_MSEC)
#define NXP_SAR_ADC_RESOLUTION		12

/* Duration of conversion phases */
#define NXP_SAR_ADC_TPT			2
#define NXP_SAR_ADC_DP			2
#define NXP_SAR_ADC_CT			((NXP_SAR_ADC_RESOLUTION + 2) * 4)
#define NXP_SAR_ADC_CONV_TIME		(NXP_SAR_ADC_TPT + NXP_SAR_ADC_CT + NXP_SAR_ADC_DP)

#define NXP_SAR_ADC_NR_CHANNELS		8

#define NXP_PAGE_SIZE			SZ_4K
#define NXP_SAR_ADC_DMA_SAMPLE_SZ	DMA_SLAVE_BUSWIDTH_4_BYTES
#define NXP_SAR_ADC_DMA_BUFF_SZ		(NXP_PAGE_SIZE * NXP_SAR_ADC_DMA_SAMPLE_SZ)
#define NXP_SAR_ADC_DMA_SAMPLE_CNT	(NXP_SAR_ADC_DMA_BUFF_SZ / NXP_SAR_ADC_DMA_SAMPLE_SZ)

struct nxp_sar_adc {
	void __iomem *regs;
	phys_addr_t regs_phys;
	u8 current_channel;
	u8 channels_used;
	u16 value;
	u32 vref_mV;

	/* Save and restore context. */
	u32 inpsamp;
	u32 pwdn;

	struct clk *clk;
	struct dma_chan	*dma_chan;
	struct completion completion;
	struct circ_buf dma_buf;

	dma_addr_t rx_dma_buf;
	dma_cookie_t cookie;

	/* Protect circular buffers access. */
	spinlock_t lock;

	/* Array of enabled channels. */
	u16 buffered_chan[NXP_SAR_ADC_NR_CHANNELS];

	/* Buffer to be filled by the DMA. */
	IIO_DECLARE_BUFFER_WITH_TS(u16, buffer, NXP_SAR_ADC_NR_CHANNELS);
};

struct nxp_sar_adc_data {
	u32 vref_mV;
	const char *model;
};

#define ADC_CHAN(_idx, _chan_type) {				\
	.type = (_chan_type),					\
	.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),	\
	.scan_index = (_idx),					\
	.scan_type = {						\
		.sign = 'u',					\
		.realbits = 12,					\
		.storagebits = 16,				\
	},							\
}

static const struct iio_chan_spec nxp_sar_adc_iio_channels[] = {
	ADC_CHAN(0, IIO_VOLTAGE),
	ADC_CHAN(1, IIO_VOLTAGE),
	ADC_CHAN(2, IIO_VOLTAGE),
	ADC_CHAN(3, IIO_VOLTAGE),
	ADC_CHAN(4, IIO_VOLTAGE),
	ADC_CHAN(5, IIO_VOLTAGE),
	ADC_CHAN(6, IIO_VOLTAGE),
	ADC_CHAN(7, IIO_VOLTAGE),
	/*
	 * The NXP SAR ADC documentation marks the channels 8 to 31 as
	 * "Reserved". Reflect the same in the driver in case new ADC
	 * variants comes with more channels.
	 */
	IIO_CHAN_SOFT_TIMESTAMP(32),
};

static void nxp_sar_adc_irq_cfg(struct nxp_sar_adc *info, bool enable)
{
	if (enable)
		writel(NXP_SAR_ADC_ISR_ECH, NXP_SAR_ADC_IMR(info->regs));
	else
		writel(0, NXP_SAR_ADC_IMR(info->regs));
}

static bool nxp_sar_adc_set_enabled(struct nxp_sar_adc *info, bool enable)
{
	u32 mcr;
	bool pwdn;

	mcr = readl(NXP_SAR_ADC_MCR(info->regs));

	/*
	 * Get the current state and return it later. This is used for
	 * suspend/resume to get the power state
	 */
	pwdn = FIELD_GET(NXP_SAR_ADC_MCR_PWDN, mcr);

	/* When the enabled flag is not set, we set the power down bit */
	FIELD_MODIFY(NXP_SAR_ADC_MCR_PWDN, &mcr, !enable);

	writel(mcr, NXP_SAR_ADC_MCR(info->regs));

	/*
	 * Ensure there are at least three cycles between the
	 * configuration of NCMR and the setting of NSTART.
	 */
	if (enable)
		ndelay(div64_u64(NSEC_PER_SEC, clk_get_rate(info->clk) * 3));

	return pwdn;
}

static inline bool nxp_sar_adc_enable(struct nxp_sar_adc *info)
{
	return nxp_sar_adc_set_enabled(info, true);
}

static inline bool nxp_sar_adc_disable(struct nxp_sar_adc *info)
{
	return nxp_sar_adc_set_enabled(info, false);
}

static inline void nxp_sar_adc_calibration_start(void __iomem *base)
{
	u32 mcr = readl(NXP_SAR_ADC_MCR(base));

	FIELD_MODIFY(NXP_SAR_ADC_MCR_CALSTART, &mcr, 0x1);

	writel(mcr, NXP_SAR_ADC_MCR(base));
}

static inline int nxp_sar_adc_calibration_wait(void __iomem *base)
{
	u32 msr;
	int ret;

	ret = readl_poll_timeout(NXP_SAR_ADC_MSR(base), msr,
				 !FIELD_GET(NXP_SAR_ADC_MSR_CALBUSY, msr),
				 NXP_SAR_ADC_WAIT_US,
				 NXP_SAR_ADC_CAL_TIMEOUT_US);
	if (ret)
		return ret;

	if (FIELD_GET(NXP_SAR_ADC_MSR_CALFAIL, msr)) {
		/*
		 * If the calibration fails, the status register bit must be
		 * cleared.
		 */
		FIELD_MODIFY(NXP_SAR_ADC_MSR_CALFAIL, &msr, 0x0);
		writel(msr, NXP_SAR_ADC_MSR(base));

		return -EAGAIN;
	}

	return 0;
}

static int nxp_sar_adc_calibration(struct nxp_sar_adc *info)
{
	int ret;

	/* Calibration works only if the ADC is powered up. */
	nxp_sar_adc_enable(info);

	/* The calibration operation starts. */
	nxp_sar_adc_calibration_start(info->regs);

	ret = nxp_sar_adc_calibration_wait(info->regs);

	/*
	 * Calibration works only if the ADC is powered up. However
	 * the calibration is called from the probe function where the
	 * iio is not enabled, so we disable after the calibration.
	 */
	nxp_sar_adc_disable(info);

	return ret;
}

static void nxp_sar_adc_conversion_timing_set(struct nxp_sar_adc *info, u32 inpsamp)
{
	inpsamp = clamp(inpsamp, NXP_SAR_ADC_CTR_INPSAMP_MIN, NXP_SAR_ADC_CTR_INPSAMP_MAX);

	writel(inpsamp, NXP_SAR_ADC_CTR0(info->regs));
}

static u32 nxp_sar_adc_conversion_timing_get(struct nxp_sar_adc *info)
{
	return readl(NXP_SAR_ADC_CTR0(info->regs));
}

static void nxp_sar_adc_read_notify(struct nxp_sar_adc *info)
{
	writel(NXP_SAR_ADC_CH_MASK, NXP_SAR_ADC_CEOCFR0(info->regs));
	writel(NXP_SAR_ADC_CH_MASK, NXP_SAR_ADC_CEOCFR1(info->regs));
}

static int nxp_sar_adc_read_data(struct nxp_sar_adc *info, unsigned int chan)
{
	u32 ceocfr, cdr;

	ceocfr = readl(NXP_SAR_ADC_CEOCFR0(info->regs));

	/*
	 * FIELD_GET() can not be used here because EOC_CH is not constant.
	 * TODO: Switch to field_get() when it will be available.
	 */
	if (!(NXP_SAR_ADC_EOC_CH(chan) & ceocfr))
		return -EIO;

	cdr = readl(NXP_SAR_ADC_CDR(info->regs, chan));
	if (!(FIELD_GET(NXP_SAR_ADC_CDR_VALID, cdr)))
		return -EIO;

	return FIELD_GET(NXP_SAR_ADC_CDR_CDATA_MASK, cdr);
}

static void nxp_sar_adc_isr_buffer(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	unsigned int i;
	int ret;

	for (i = 0; i < info->channels_used; i++) {
		ret = nxp_sar_adc_read_data(info, info->buffered_chan[i]);
		if (ret < 0) {
			nxp_sar_adc_read_notify(info);
			return;
		}

		info->buffer[i] = ret;
	}

	nxp_sar_adc_read_notify(info);

	iio_push_to_buffers_with_ts(indio_dev, info->buffer, sizeof(info->buffer),
				    iio_get_time_ns(indio_dev));

	iio_trigger_notify_done(indio_dev->trig);
}

static void nxp_sar_adc_isr_read_raw(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int ret;

	ret = nxp_sar_adc_read_data(info, info->current_channel);
	nxp_sar_adc_read_notify(info);
	if (ret < 0)
		return;

	info->value = ret;
	complete(&info->completion);
}

static irqreturn_t nxp_sar_adc_isr(int irq, void *dev_id)
{
	struct iio_dev *indio_dev = dev_id;
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int isr;

	isr = readl(NXP_SAR_ADC_ISR(info->regs));
	if (!(FIELD_GET(NXP_SAR_ADC_ISR_ECH, isr)))
		return IRQ_NONE;

	if (iio_buffer_enabled(indio_dev))
		nxp_sar_adc_isr_buffer(indio_dev);
	else
		nxp_sar_adc_isr_read_raw(indio_dev);

	writel(NXP_SAR_ADC_ISR_ECH, NXP_SAR_ADC_ISR(info->regs));

	return IRQ_HANDLED;
}

static void nxp_sar_adc_channels_disable(struct nxp_sar_adc *info, u32 mask)
{
	u32 ncmr, cimr;

	ncmr = readl(NXP_SAR_ADC_NCMR0(info->regs));
	cimr = readl(NXP_SAR_ADC_CIMR0(info->regs));

	/* FIELD_MODIFY() can not be used because the mask is not constant */
	ncmr &= ~mask;
	cimr &= ~mask;

	writel(ncmr, NXP_SAR_ADC_NCMR0(info->regs));
	writel(cimr, NXP_SAR_ADC_CIMR0(info->regs));
}

static void nxp_sar_adc_channels_enable(struct nxp_sar_adc *info, u32 mask)
{
	u32 ncmr, cimr;

	ncmr = readl(NXP_SAR_ADC_NCMR0(info->regs));
	cimr = readl(NXP_SAR_ADC_CIMR0(info->regs));

	ncmr |= mask;
	cimr |= mask;

	writel(ncmr, NXP_SAR_ADC_NCMR0(info->regs));
	writel(cimr, NXP_SAR_ADC_CIMR0(info->regs));
}

static void nxp_sar_adc_dma_channels_enable(struct nxp_sar_adc *info, u32 mask)
{
	u32 dmar;

	dmar = readl(NXP_SAR_ADC_DMAR0(info->regs));

	dmar |= mask;

	writel(dmar, NXP_SAR_ADC_DMAR0(info->regs));
}

static void nxp_sar_adc_dma_channels_disable(struct nxp_sar_adc *info, u32 mask)
{
	u32 dmar;

	dmar = readl(NXP_SAR_ADC_DMAR0(info->regs));

	dmar &= ~mask;

	writel(dmar, NXP_SAR_ADC_DMAR0(info->regs));
}

static void nxp_sar_adc_dma_cfg(struct nxp_sar_adc *info, bool enable)
{
	u32 dmae;

	dmae = readl(NXP_SAR_ADC_DMAE(info->regs));

	FIELD_MODIFY(NXP_SAR_ADC_DMAE_DMAEN, &dmae, enable);

	writel(dmae, NXP_SAR_ADC_DMAE(info->regs));
}

static void nxp_sar_adc_stop_conversion(struct nxp_sar_adc *info)
{
	u32 mcr;

	mcr = readl(NXP_SAR_ADC_MCR(info->regs));

	FIELD_MODIFY(NXP_SAR_ADC_MCR_NSTART, &mcr, 0x0);

	writel(mcr, NXP_SAR_ADC_MCR(info->regs));

	/*
	 * On disable, we have to wait for the transaction to finish.
	 * ADC does not abort the transaction if a chain conversion is
	 * in progress. Wait for the worst case scenario - 80 ADC clk
	 * cycles. The clock rate is 80MHz, this routine is called
	 * only when the capture finishes. The delay will be very
	 * short, usec-ish, which is acceptable in the atomic context.
	 */
	ndelay(div64_u64(NSEC_PER_SEC, clk_get_rate(info->clk)) * 80);
}

static int nxp_sar_adc_start_conversion(struct nxp_sar_adc *info, bool raw)
{
	u32 mcr;

	mcr = readl(NXP_SAR_ADC_MCR(info->regs));

	FIELD_MODIFY(NXP_SAR_ADC_MCR_NSTART, &mcr, 0x1);
	FIELD_MODIFY(NXP_SAR_ADC_MCR_MODE, &mcr, raw ? 0 : 1);

	writel(mcr, NXP_SAR_ADC_MCR(info->regs));

	return 0;
}

static int nxp_sar_adc_read_channel(struct nxp_sar_adc *info, int channel)
{
	int ret;

	info->current_channel = channel;
	nxp_sar_adc_channels_enable(info, BIT(channel));
	nxp_sar_adc_irq_cfg(info, true);
	nxp_sar_adc_enable(info);

	reinit_completion(&info->completion);
	ret = nxp_sar_adc_start_conversion(info, true);
	if (ret < 0)
		goto out_disable;

	if (!wait_for_completion_interruptible_timeout(&info->completion,
						       NXP_SAR_ADC_CONV_TIMEOUT))
		ret = -ETIMEDOUT;

	nxp_sar_adc_stop_conversion(info);

out_disable:
	nxp_sar_adc_channels_disable(info, BIT(channel));
	nxp_sar_adc_irq_cfg(info, false);
	nxp_sar_adc_disable(info);

	return ret;
}

static int nxp_sar_adc_read_raw(struct iio_dev *indio_dev,
				struct iio_chan_spec const *chan, int *val,
				int *val2, long mask)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	u32 inpsamp;
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (!iio_device_claim_direct(indio_dev))
			return -EBUSY;

		ret = nxp_sar_adc_read_channel(info, chan->channel);

		iio_device_release_direct(indio_dev);

		if (ret)
			return ret;

		*val = info->value;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		*val = info->vref_mV;
		*val2 = NXP_SAR_ADC_RESOLUTION;
		return IIO_VAL_FRACTIONAL_LOG2;

	case IIO_CHAN_INFO_SAMP_FREQ:
		inpsamp = nxp_sar_adc_conversion_timing_get(info);
		*val = clk_get_rate(info->clk) / (inpsamp + NXP_SAR_ADC_CONV_TIME);
		return IIO_VAL_INT;

	default:
		return -EINVAL;
	}
}

static int nxp_sar_adc_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
				 int val, int val2, long mask)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	u32 inpsamp;

	switch (mask) {
	case IIO_CHAN_INFO_SAMP_FREQ:
		/*
		 * Configures the sample period duration in terms of the SAR
		 * controller clock. The minimum acceptable value is 8.
		 * Configuring it to a value lower than 8 sets the sample period
		 * to 8 cycles.  We read the clock value and divide by the
		 * sampling timing which gives us the number of cycles expected.
		 * The value is 8-bit wide, consequently the max value is 0xFF.
		 */
		inpsamp = clk_get_rate(info->clk) / val - NXP_SAR_ADC_CONV_TIME;
		nxp_sar_adc_conversion_timing_set(info, inpsamp);
		return 0;

	default:
		return -EINVAL;
	}
}

static void nxp_sar_adc_dma_cb(void *data)
{
	struct iio_dev *indio_dev = data;
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	struct dma_tx_state state;
	struct circ_buf *dma_buf;
	struct device *dev_dma;
	u32 *dma_samples;
	s64 timestamp;
	int idx, ret;

	guard(spinlock_irqsave)(&info->lock);

	dma_buf = &info->dma_buf;
	dma_samples = (u32 *)dma_buf->buf;
	dev_dma = info->dma_chan->device->dev;

	/*
	 * DMA in some corner cases might have already be charged for
	 * the next transfer. Potentially there can be a race where
	 * the residue changes while the dma engine updates the
	 * buffer. That could be handled by using the
	 * callback_result() instead of callback() because the residue
	 * will be passed as a parameter to the function. However this
	 * new callback is pretty new and the backend does not update
	 * the residue. So let's stick to the version other drivers do
	 * which has proven running well in production since several
	 * years.
	 */
	dmaengine_tx_status(info->dma_chan, info->cookie, &state);

	dma_sync_single_for_cpu(dev_dma, info->rx_dma_buf,
				NXP_SAR_ADC_DMA_BUFF_SZ, DMA_FROM_DEVICE);

	/* Current head position. */
	dma_buf->head = (NXP_SAR_ADC_DMA_BUFF_SZ - state.residue) /
			NXP_SAR_ADC_DMA_SAMPLE_SZ;

	/* If everything was transferred, avoid an off by one error. */
	if (!state.residue)
		dma_buf->head--;

	/* Something went wrong and nothing transferred. */
	if (state.residue != NXP_SAR_ADC_DMA_BUFF_SZ) {
		/* Make sure that head is multiple of info->channels_used. */
		dma_buf->head -= dma_buf->head % info->channels_used;

		/*
		 * dma_buf->tail != dma_buf->head condition will become false
		 * because dma_buf->tail will be incremented with 1.
		 */
		while (dma_buf->tail != dma_buf->head) {
			idx = dma_buf->tail % info->channels_used;
			info->buffer[idx] = dma_samples[dma_buf->tail];
			dma_buf->tail = (dma_buf->tail + 1) % NXP_SAR_ADC_DMA_SAMPLE_CNT;
			if (idx != info->channels_used - 1)
				continue;

			/*
			 * iio_push_to_buffers_with_ts() should not be
			 * called with dma_samples as parameter. The samples
			 * will be smashed if timestamp is enabled.
			 */
			timestamp = iio_get_time_ns(indio_dev);
			ret = iio_push_to_buffers_with_ts(indio_dev, info->buffer,
							  sizeof(info->buffer),
							  timestamp);
			if (ret < 0 && ret != -EBUSY)
				dev_err_ratelimited(&indio_dev->dev,
						    "failed to push iio buffer: %d",
						    ret);
		}

		dma_buf->tail = dma_buf->head;
	}

	dma_sync_single_for_device(dev_dma, info->rx_dma_buf,
				   NXP_SAR_ADC_DMA_BUFF_SZ, DMA_FROM_DEVICE);
}

static int nxp_sar_adc_start_cyclic_dma(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	struct dma_slave_config config;
	struct dma_async_tx_descriptor *desc;
	int ret;

	info->dma_buf.head = 0;
	info->dma_buf.tail = 0;

	config.direction = DMA_DEV_TO_MEM;
	config.src_addr_width = NXP_SAR_ADC_DMA_SAMPLE_SZ;
	config.src_addr = NXP_SAR_ADC_CDR(info->regs_phys, info->buffered_chan[0]);
	config.src_port_window_size = info->channels_used;
	config.src_maxburst = info->channels_used;
	ret = dmaengine_slave_config(info->dma_chan, &config);
	if (ret < 0)
		return ret;

	desc = dmaengine_prep_dma_cyclic(info->dma_chan,
					 info->rx_dma_buf,
					 NXP_SAR_ADC_DMA_BUFF_SZ,
					 NXP_SAR_ADC_DMA_BUFF_SZ / 2,
					 DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT);
	if (!desc)
		return -EINVAL;

	desc->callback = nxp_sar_adc_dma_cb;
	desc->callback_param = indio_dev;
	info->cookie = dmaengine_submit(desc);
	ret = dma_submit_error(info->cookie);
	if (ret) {
		dmaengine_terminate_async(info->dma_chan);
		return ret;
	}

	dma_async_issue_pending(info->dma_chan);

	return 0;
}

static void nxp_sar_adc_buffer_software_do_predisable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);

	/*
	 * The ADC DMAEN bit should be cleared before DMA transaction
	 * is canceled.
	 */
	nxp_sar_adc_stop_conversion(info);
	dmaengine_terminate_sync(info->dma_chan);
	nxp_sar_adc_dma_cfg(info, false);
	nxp_sar_adc_dma_channels_disable(info, *indio_dev->active_scan_mask);

	dma_release_channel(info->dma_chan);
}

static int nxp_sar_adc_buffer_software_do_postenable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int ret;

	info->dma_chan = dma_request_chan(indio_dev->dev.parent, "rx");
	if (IS_ERR(info->dma_chan))
		return PTR_ERR(info->dma_chan);

	nxp_sar_adc_dma_channels_enable(info, *indio_dev->active_scan_mask);

	nxp_sar_adc_dma_cfg(info, true);

	ret = nxp_sar_adc_start_cyclic_dma(indio_dev);
	if (ret)
		goto out_dma_channels_disable;

	ret = nxp_sar_adc_start_conversion(info, false);
	if (ret)
		goto out_stop_cyclic_dma;

	return 0;

out_stop_cyclic_dma:
	dmaengine_terminate_sync(info->dma_chan);

out_dma_channels_disable:
	nxp_sar_adc_dma_cfg(info, false);
	nxp_sar_adc_dma_channels_disable(info, *indio_dev->active_scan_mask);
	dma_release_channel(info->dma_chan);

	return ret;
}

static void nxp_sar_adc_buffer_trigger_do_predisable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);

	nxp_sar_adc_irq_cfg(info, false);
}

static int nxp_sar_adc_buffer_trigger_do_postenable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);

	nxp_sar_adc_irq_cfg(info, true);

	return 0;
}

static int nxp_sar_adc_buffer_postenable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int current_mode = iio_device_get_current_mode(indio_dev);
	unsigned long channel;
	int ret;

	info->channels_used = 0;

	/*
	 * The SAR-ADC has two groups of channels.
	 *
	 *	- Group #0:
	 *	* bit 0-7  : channel 0 -> channel 7
	 *	* bit 8-31 : reserved
	 *
	 *	- Group #32:
	 *	* bit 0-7  : Internal
	 *	* bit 8-31 : reserved
	 *
	 * The 8 channels from group #0 are used in this driver for
	 * ADC as described when declaring the IIO device and the
	 * mapping is the same. That means the active_scan_mask can be
	 * used directly to write the channel interrupt mask.
	 */
	nxp_sar_adc_channels_enable(info, *indio_dev->active_scan_mask);

	for_each_set_bit(channel, indio_dev->active_scan_mask, NXP_SAR_ADC_NR_CHANNELS)
		info->buffered_chan[info->channels_used++] = channel;

	nxp_sar_adc_enable(info);

	if (current_mode == INDIO_BUFFER_SOFTWARE)
		ret = nxp_sar_adc_buffer_software_do_postenable(indio_dev);
	else
		ret = nxp_sar_adc_buffer_trigger_do_postenable(indio_dev);
	if (ret)
		goto out_postenable;

	return 0;

out_postenable:
	nxp_sar_adc_disable(info);
	nxp_sar_adc_channels_disable(info, *indio_dev->active_scan_mask);

	return ret;
}

static int nxp_sar_adc_buffer_predisable(struct iio_dev *indio_dev)
{
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int currentmode = iio_device_get_current_mode(indio_dev);

	if (currentmode == INDIO_BUFFER_SOFTWARE)
		nxp_sar_adc_buffer_software_do_predisable(indio_dev);
	else
		nxp_sar_adc_buffer_trigger_do_predisable(indio_dev);

	nxp_sar_adc_disable(info);

	nxp_sar_adc_channels_disable(info, *indio_dev->active_scan_mask);

	return 0;
}

static irqreturn_t nxp_sar_adc_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct nxp_sar_adc *info = iio_priv(indio_dev);
	int ret;

	ret = nxp_sar_adc_start_conversion(info, true);
	if (ret < 0)
		dev_dbg(&indio_dev->dev, "Failed to start conversion\n");

	return IRQ_HANDLED;
}

static const struct iio_buffer_setup_ops iio_triggered_buffer_setup_ops = {
	.postenable = nxp_sar_adc_buffer_postenable,
	.predisable = nxp_sar_adc_buffer_predisable,
};

static const struct iio_info nxp_sar_adc_iio_info = {
	.read_raw  = nxp_sar_adc_read_raw,
	.write_raw = nxp_sar_adc_write_raw,
};

static int nxp_sar_adc_dma_probe(struct device *dev, struct nxp_sar_adc *info)
{
	u8 *rx_buf;

	rx_buf = dmam_alloc_coherent(dev, NXP_SAR_ADC_DMA_BUFF_SZ,
				     &info->rx_dma_buf, GFP_KERNEL);
	if (!rx_buf)
		return -ENOMEM;

	info->dma_buf.buf = rx_buf;

	return 0;
}

/*
 * The documentation describes the reset values for the registers.
 * However some registers do not have these values after a reset. It
 * is not a desirable situation. In some other SoC family
 * documentation NXP recommends not assuming the default values are
 * set and to initialize the registers conforming to the documentation
 * reset information to prevent this situation. Assume the same rule
 * applies here as there is a discrepancy between what is read from
 * the registers at reset time and the documentation.
 */
static void nxp_sar_adc_set_default_values(struct nxp_sar_adc *info)
{
	writel(0x00003901, NXP_SAR_ADC_MCR(info->regs));
	writel(0x00000001, NXP_SAR_ADC_MSR(info->regs));
	writel(0x00000014, NXP_SAR_ADC_CTR0(info->regs));
	writel(0x00000014, NXP_SAR_ADC_CTR1(info->regs));
	writel(0x00000000, NXP_SAR_ADC_CIMR0(info->regs));
	writel(0x00000000, NXP_SAR_ADC_CIMR1(info->regs));
	writel(0x00000000, NXP_SAR_ADC_NCMR0(info->regs));
	writel(0x00000000, NXP_SAR_ADC_NCMR1(info->regs));
}

static int nxp_sar_adc_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	const struct nxp_sar_adc_data *data = device_get_match_data(dev);
	struct nxp_sar_adc *info;
	struct iio_dev *indio_dev;
	struct resource *mem;
	int irq, ret;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*info));
	if (!indio_dev)
		return -ENOMEM;

	info = iio_priv(indio_dev);
	info->vref_mV = data->vref_mV;
	spin_lock_init(&info->lock);
	info->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &mem);
	if (IS_ERR(info->regs))
		return dev_err_probe(dev, PTR_ERR(info->regs),
				     "Failed to get and remap resource");

	info->regs_phys = mem->start;

	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
		return irq;

	ret = devm_request_irq(dev, irq, nxp_sar_adc_isr, 0, dev_name(dev),
			       indio_dev);
	if (ret < 0)
		return ret;

	info->clk = devm_clk_get_enabled(dev, NULL);
	if (IS_ERR(info->clk))
		return dev_err_probe(dev, PTR_ERR(info->clk),
				     "Failed to get the clock\n");

	platform_set_drvdata(pdev, indio_dev);

	init_completion(&info->completion);

	indio_dev->name = data->model;
	indio_dev->info = &nxp_sar_adc_iio_info;
	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
	indio_dev->channels = nxp_sar_adc_iio_channels;
	indio_dev->num_channels = ARRAY_SIZE(nxp_sar_adc_iio_channels);

	nxp_sar_adc_set_default_values(info);

	ret = nxp_sar_adc_calibration(info);
	if (ret)
		dev_err_probe(dev, ret, "Calibration failed\n");

	ret = nxp_sar_adc_dma_probe(dev, info);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to initialize the DMA\n");

	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
					      &iio_pollfunc_store_time,
					      &nxp_sar_adc_trigger_handler,
					      &iio_triggered_buffer_setup_ops);
	if (ret < 0)
		return dev_err_probe(dev, ret, "Couldn't initialise the buffer\n");

	ret = devm_iio_device_register(dev, indio_dev);
	if (ret)
		return dev_err_probe(dev, ret, "Couldn't register the device\n");

	return 0;
}

static int nxp_sar_adc_suspend(struct device *dev)
{
	struct nxp_sar_adc *info = iio_priv(dev_get_drvdata(dev));

	info->pwdn = nxp_sar_adc_disable(info);
	info->inpsamp = nxp_sar_adc_conversion_timing_get(info);

	clk_disable_unprepare(info->clk);

	return 0;
}

static int nxp_sar_adc_resume(struct device *dev)
{
	struct nxp_sar_adc *info = iio_priv(dev_get_drvdata(dev));
	int ret;

	ret = clk_prepare_enable(info->clk);
	if (ret)
		return ret;

	nxp_sar_adc_conversion_timing_set(info, info->inpsamp);

	if (!info->pwdn)
		nxp_sar_adc_enable(info);

	return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(nxp_sar_adc_pm_ops, nxp_sar_adc_suspend,
				nxp_sar_adc_resume);

static const struct nxp_sar_adc_data s32g2_sar_adc_data = {
	.vref_mV = 1800,
	.model = "s32g2-sar-adc",
};

static const struct of_device_id nxp_sar_adc_match[] = {
	{ .compatible = "nxp,s32g2-sar-adc", .data = &s32g2_sar_adc_data },
	{ }
};
MODULE_DEVICE_TABLE(of, nxp_sar_adc_match);

static struct platform_driver nxp_sar_adc_driver = {
	.probe = nxp_sar_adc_probe,
	.driver = {
		.name = "nxp-sar-adc",
		.of_match_table = nxp_sar_adc_match,
		.pm = pm_sleep_ptr(&nxp_sar_adc_pm_ops),
	},
};
module_platform_driver(nxp_sar_adc_driver);

MODULE_AUTHOR("NXP");
MODULE_DESCRIPTION("NXP SAR-ADC driver");
MODULE_LICENSE("GPL");