Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

[Andy Shevchenko]

On Fri, Mar 20, 2026 at 01:03:58PM +0200, Radu Sabau via B4 Relay wrote:

> Add SPI offload support to enable DMA-based, CPU-independent data
> acquisition using the SPI Engine offload framework.
> 
> When an SPI offload is available (devm_spi_offload_get() succeeds),
> the driver registers a DMA engine IIO buffer and uses dedicated buffer
> setup operations. If no offload is available the existing software
> triggered buffer path is used unchanged.
> 
> Both CNV Burst Mode and Manual Mode support offload, but use different
> trigger mechanisms:
> 
> CNV Burst Mode: the SPI Engine is triggered by the ADC's DATA_READY
> signal on the GP pin specified by the trigger-source consumer reference
> in the device tree (one cell = GP pin number 0-3). For this mode the
> driver acts as both an SPI offload consumer (DMA RX stream, message
> optimization) and a trigger source provider: it registers the
> GP/DATA_READY output via devm_spi_offload_trigger_register() so the
> offload framework can match the '#trigger-source-cells' phandle and
> automatically fire the SPI Engine DMA transfer at end-of-conversion.
> 
> Manual Mode: the SPI Engine is triggered by a periodic trigger at
> the configured sampling frequency. The pre-built SPI message uses
> the pipelined CNV-on-CS protocol: N+1 4-byte transfers are issued
> for N active channels (the first result is discarded as garbage from
> the pipeline flush) and the remaining N results are captured by DMA.
> 
> All offload transfers use 32-bit frames (bits_per_word=32, len=4) for
> DMA word alignment. This patch promotes the channel scan_type from
> storagebits=16 (triggered-buffer path) to storagebits=32 to match the
> DMA word size; the triggered-buffer paths are updated to the same layout
> for consistency. CNV Burst Mode channel data arrives in the lower 16
> bits of the 32-bit word (shift=0); Manual Mode data arrives in the upper
> 16 bits (shift=16), matching the 4-byte SPI transfer layout
> [data_hi, data_lo, 0, 0]. A separate ad4691_manual_channels[] array
> encodes the shift=16 scan type for manual mode.
> 
> Kconfig gains a dependency on IIO_BUFFER_DMAENGINE.

...

> +	struct spi_offload		*offload;
> +	/* SPI offload trigger - periodic (MANUAL) or DATA_READY (CNV_BURST) */
> +	struct spi_offload_trigger	*offload_trigger;
> +	u64				offload_trigger_hz;
> +	struct spi_message		offload_msg;
> +	/* Max 16 channel xfers + 1 state-reset or NOOP */
> +	struct spi_transfer		offload_xfer[17];
> +	u32				offload_tx_cmd[17];
> +	u32				offload_tx_reset;

Ouch! Can you guarantee this kilobytes (isn't it?) of memory will be used in
majority of the cases? When I got comment on replacing a single u8 by unsigned
long in one well used data structure in the kernel I was laughing, but this
single driver may beat the recode of memory waste on the embedded platforms.
Perhaps having a separate structure and allocate it separately when we sure
the offload is supported?

Cc'ed to Wolfram.

...

> +	/* Scan buffer: one slot per channel (u32) plus timestamp */
>  	struct {
> -		u16 vals[16];
> +		u32 vals[16];
>  		s64 ts __aligned(8);

This might break the existing cases or make code ugly and not actually
compatible with u32 layout.

>  	} scan __aligned(IIO_DMA_MINALIGN);

...

> +static int ad4691_cnv_burst_offload_buffer_postenable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct spi_device *spi = to_spi_device(dev);
> +	struct spi_offload_trigger_config config = {
> +		.type = SPI_OFFLOAD_TRIGGER_DATA_READY,
> +	};

> +	unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);

Should be bitmap_weight() with properly given amount of bits.


> +	unsigned int bit, k;
> +	int ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~(*indio_dev->active_scan_mask));

This is not how we work with bitmaps. Use bitmap_read().

> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   *indio_dev->active_scan_mask);

Ditto.

> +	if (ret)
> +		return ret;
> +
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		ret = regmap_write(st->regmap, AD4691_ACC_COUNT_LIMIT(bit),
> +				   AD4691_ACC_COUNT_VAL);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = ad4691_enter_conversion_mode(st);
> +	if (ret)
> +		return ret;
> +
> +	memset(st->offload_xfer, 0, sizeof(st->offload_xfer));
> +
> +	/*
> +	 * N transfers to read N AVG_IN registers plus one state-reset
> +	 * transfer (no RX) to re-arm DATA_READY.
> +	 *   TX: [reg_hi | 0x80, reg_lo, 0x00, 0x00]
> +	 *   RX: [0x00, 0x00, data_hi, data_lo]   (shift=0)
> +	 */
> +	k = 0;
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		unsigned int reg = AD4691_AVG_IN(bit);
> +
> +		st->offload_tx_cmd[k] =

> +			cpu_to_be32(((reg >> 8 | 0x80) << 24) |
> +				    ((reg & 0xFF) << 16));

Isn't this is just a cpu_to_be16(0x8000 | reg) ?

> +		st->offload_xfer[k].tx_buf = &st->offload_tx_cmd[k];
> +		st->offload_xfer[k].len = sizeof(u32);
> +		st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
> +		st->offload_xfer[k].offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
> +		if (k < n_active - 1)
> +			st->offload_xfer[k].cs_change = 1;
> +		k++;
> +	}
> +
> +	/* State reset to re-arm DATA_READY for the next scan. */
> +	st->offload_tx_reset =
> +		cpu_to_be32(((AD4691_STATE_RESET_REG >> 8) << 24) |
> +			    ((AD4691_STATE_RESET_REG & 0xFF) << 16) |
> +			    (AD4691_STATE_RESET_ALL << 8));

In similar way

		cpu_to_be32((AD4691_STATE_RESET_REG << 16) |
			    (AD4691_STATE_RESET_ALL << 8));

> +	st->offload_xfer[k].tx_buf = &st->offload_tx_reset;
> +	st->offload_xfer[k].len = sizeof(u32);
> +	st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
> +	k++;
> +
> +	spi_message_init_with_transfers(&st->offload_msg, st->offload_xfer, k);
> +	st->offload_msg.offload = st->offload;
> +
> +	ret = spi_optimize_message(spi, &st->offload_msg);
> +	if (ret)
> +		goto err_exit_conversion;
> +
> +	ret = ad4691_sampling_enable(st, true);
> +	if (ret)
> +		goto err_unoptimize;
> +
> +	ret = spi_offload_trigger_enable(st->offload, st->offload_trigger, &config);
> +	if (ret)
> +		goto err_sampling_disable;
> +
> +	return 0;
> +
> +err_sampling_disable:
> +	ad4691_sampling_enable(st, false);
> +err_unoptimize:
> +	spi_unoptimize_message(&st->offload_msg);
> +err_exit_conversion:
> +	ad4691_exit_conversion_mode(st);
> +	return ret;
> +}

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

[Jonathan Cameron]

On Fri, 20 Mar 2026 13:03:58 +0200
Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org> wrote:

> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add SPI offload support to enable DMA-based, CPU-independent data
> acquisition using the SPI Engine offload framework.
> 
> When an SPI offload is available (devm_spi_offload_get() succeeds),
> the driver registers a DMA engine IIO buffer and uses dedicated buffer
> setup operations. If no offload is available the existing software
> triggered buffer path is used unchanged.
> 
> Both CNV Burst Mode and Manual Mode support offload, but use different
> trigger mechanisms:
> 
> CNV Burst Mode: the SPI Engine is triggered by the ADC's DATA_READY
> signal on the GP pin specified by the trigger-source consumer reference
> in the device tree (one cell = GP pin number 0-3). For this mode the
> driver acts as both an SPI offload consumer (DMA RX stream, message
> optimization) and a trigger source provider: it registers the
> GP/DATA_READY output via devm_spi_offload_trigger_register() so the
> offload framework can match the '#trigger-source-cells' phandle and
> automatically fire the SPI Engine DMA transfer at end-of-conversion.
> 
> Manual Mode: the SPI Engine is triggered by a periodic trigger at
> the configured sampling frequency. The pre-built SPI message uses
> the pipelined CNV-on-CS protocol: N+1 4-byte transfers are issued
> for N active channels (the first result is discarded as garbage from
> the pipeline flush) and the remaining N results are captured by DMA.
> 
> All offload transfers use 32-bit frames (bits_per_word=32, len=4) for
> DMA word alignment. This patch promotes the channel scan_type from
> storagebits=16 (triggered-buffer path) to storagebits=32 to match the
> DMA word size; the triggered-buffer paths are updated to the same layout
> for consistency. 

That's quite a large cost for the kfifo sizing, particularly if timestamps
are enabled. I think I'd prefer we kept the exiting paths using 16 bit data
storage for each channel.

> CNV Burst Mode channel data arrives in the lower 16
> bits of the 32-bit word (shift=0); Manual Mode data arrives in the upper
> 16 bits (shift=16), matching the 4-byte SPI transfer layout
> [data_hi, data_lo, 0, 0]. A separate ad4691_manual_channels[] array
> encodes the shift=16 scan type for manual mode.

That's odd - but fair enough if that's what the IP ends up doing.

> 
> Kconfig gains a dependency on IIO_BUFFER_DMAENGINE.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>

Various other minor comments inline.

> -#define AD4691_CHANNEL(ch)						\
> +/*
> + * 16-bit ADC data is stored in 32-bit slots to match the SPI offload DMA
> + * word size (32 bits per transfer). The shift reflects the data position

As mentioned elsewhere, I don't think we care about matching the offload
layout. Lots of existing drivers don't and if we can we want to minimize
wasted space whilst still keep the data naturally aligned to make accesses easy.

> + * within the 32-bit word:
> + *   CNV_BURST: RX = [dummy, dummy, data_hi, data_lo] -> shift = 0
> + *   MANUAL:    RX = [data_hi, data_lo, dummy, dummy] -> shift = 16
> + * The triggered-buffer paths store data in the same position for consistency.
> + * Do not "fix" storagebits to 16.
> + */
> +#define AD4691_CHANNEL(ch, _shift)					\
>  	{								\
>  		.type = IIO_VOLTAGE,					\
>  		.indexed = 1,						\
> @@ -118,40 +140,72 @@ struct ad4691_chip_info {
>  		.scan_type = {						\
>  			.sign = 'u',					\
>  			.realbits = 16,					\
> -			.storagebits = 16,				\
> -			.shift = 0,					\
> +			.storagebits = 32,				\
> +			.shift = _shift,				\
>  		},							\
>  	}

> @@ -227,9 +285,9 @@ struct ad4691_state {
>  	 */
>  	struct mutex			lock;
>  	/*
> -	 * Per-buffer-enabl ree lifetimesources:
> -	 * Manual Mode - a pre-built SPI message that clocks out N+1
> -	 *		 transfers in one go.
> +	 * Per-buffer-enable lifetime resources (triggered-buffer paths):
> +	 * Manual Mode    - a pre-built SPI message that clocks out N+1
> +	 *		    transfers in one go.
>  	 * CNV Burst Mode - a pre-built SPI message that clocks out 2*N
>  	 *		    transfers in one go.
>  	 */
> @@ -238,9 +296,19 @@ struct ad4691_state {
>  	struct spi_transfer		*scan_xfers;
>  	__be16				*scan_tx;
>  	__be16				*scan_rx;
> -	/* Scan buffer: one slot per channel (u16) plus timestamp */
> +	/* SPI offload DMA path resources */
> +	struct spi_offload		*offload;
> +	/* SPI offload trigger - periodic (MANUAL) or DATA_READY (CNV_BURST) */
> +	struct spi_offload_trigger	*offload_trigger;
> +	u64				offload_trigger_hz;
> +	struct spi_message		offload_msg;
> +	/* Max 16 channel xfers + 1 state-reset or NOOP */
> +	struct spi_transfer		offload_xfer[17];
> +	u32				offload_tx_cmd[17];

Andy already commented on this being large.  Allocating separately
probably makes sense.

> +	u32				offload_tx_reset;
> +	/* Scan buffer: one slot per channel (u32) plus timestamp */
>  	struct {
> -		u16 vals[16];
> +		u32 vals[16];
>  		s64 ts __aligned(8);
>  	} scan __aligned(IIO_DMA_MINALIGN);
>  };


> +static int ad4691_cnv_burst_offload_buffer_postenable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct spi_device *spi = to_spi_device(dev);
> +	struct spi_offload_trigger_config config = {
> +		.type = SPI_OFFLOAD_TRIGGER_DATA_READY,
> +	};
> +	unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);
> +	unsigned int bit, k;
> +	int ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~(*indio_dev->active_scan_mask));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   *indio_dev->active_scan_mask);
> +	if (ret)
> +		return ret;
> +
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		ret = regmap_write(st->regmap, AD4691_ACC_COUNT_LIMIT(bit),
> +				   AD4691_ACC_COUNT_VAL);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = ad4691_enter_conversion_mode(st);
> +	if (ret)
> +		return ret;
> +
> +	memset(st->offload_xfer, 0, sizeof(st->offload_xfer));
> +
> +	/*
> +	 * N transfers to read N AVG_IN registers plus one state-reset
> +	 * transfer (no RX) to re-arm DATA_READY.
> +	 *   TX: [reg_hi | 0x80, reg_lo, 0x00, 0x00]
> +	 *   RX: [0x00, 0x00, data_hi, data_lo]   (shift=0)
> +	 */
> +	k = 0;
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		unsigned int reg = AD4691_AVG_IN(bit);
> +
> +		st->offload_tx_cmd[k] =
> +			cpu_to_be32(((reg >> 8 | 0x80) << 24) |
> +				    ((reg & 0xFF) << 16));

This is an odd looking construct. Maybe it's worth casting offload_tx_cmd[k] to
a u8 * and just filling the two bytes in directly.

> +		st->offload_xfer[k].tx_buf = &st->offload_tx_cmd[k];
> +		st->offload_xfer[k].len = sizeof(u32);
> +		st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
> +		st->offload_xfer[k].offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
> +		if (k < n_active - 1)
> +			st->offload_xfer[k].cs_change = 1;
> +		k++;
> +	}
> +
> +	/* State reset to re-arm DATA_READY for the next scan. */
> +	st->offload_tx_reset =
> +		cpu_to_be32(((AD4691_STATE_RESET_REG >> 8) << 24) |
> +			    ((AD4691_STATE_RESET_REG & 0xFF) << 16) |
> +			    (AD4691_STATE_RESET_ALL << 8));
Similar to above. Feels like we should be manipulating this as a u8[4]

> +	st->offload_xfer[k].tx_buf = &st->offload_tx_reset;
> +	st->offload_xfer[k].len = sizeof(u32);
> +	st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
> +	k++;
> +
> +	spi_message_init_with_transfers(&st->offload_msg, st->offload_xfer, k);
> +	st->offload_msg.offload = st->offload;
> +
> +	ret = spi_optimize_message(spi, &st->offload_msg);
> +	if (ret)
> +		goto err_exit_conversion;
> +
> +	ret = ad4691_sampling_enable(st, true);
> +	if (ret)
> +		goto err_unoptimize;
> +
> +	ret = spi_offload_trigger_enable(st->offload, st->offload_trigger, &config);
> +	if (ret)
> +		goto err_sampling_disable;
> +
> +	return 0;
> +
> +err_sampling_disable:
> +	ad4691_sampling_enable(st, false);
> +err_unoptimize:
> +	spi_unoptimize_message(&st->offload_msg);
> +err_exit_conversion:
> +	ad4691_exit_conversion_mode(st);
> +	return ret;
> +}

Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

[kernel test robot]

Hi Radu,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 11439c4635edd669ae435eec308f4ab8a0804808]

url:    https://github.com/intel-lab-lkp/linux/commits/Radu-Sabau-via-B4-Relay/dt-bindings-iio-adc-add-AD4691-family/20260321-120718
base:   11439c4635edd669ae435eec308f4ab8a0804808
patch link:    https://lore.kernel.org/r/20260320-ad4692-multichannel-sar-adc-driver-v4-4-052c1050507a%40analog.com
patch subject: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support
config: nios2-randconfig-r122-20260322 (https://download.01.org/0day-ci/archive/20260322/202603221011.rzczUvUN-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 11.5.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260322/202603221011.rzczUvUN-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603221011.rzczUvUN-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/iio/adc/ad4691.c:954:39: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int @@     got restricted __be32 [usertype] @@
   drivers/iio/adc/ad4691.c:954:39: sparse:     expected unsigned int
   drivers/iio/adc/ad4691.c:954:39: sparse:     got restricted __be32 [usertype]
   drivers/iio/adc/ad4691.c:970:31: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int @@     got restricted __be32 [usertype] @@
   drivers/iio/adc/ad4691.c:970:31: sparse:     expected unsigned int
   drivers/iio/adc/ad4691.c:970:31: sparse:     got restricted __be32 [usertype]
   drivers/iio/adc/ad4691.c:1059:39: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int @@     got restricted __be32 [usertype] @@
   drivers/iio/adc/ad4691.c:1059:39: sparse:     expected unsigned int
   drivers/iio/adc/ad4691.c:1059:39: sparse:     got restricted __be32 [usertype]
>> drivers/iio/adc/ad4691.c:1072:30: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int [usertype] offload_tx_reset @@     got restricted __be32 [usertype] @@
   drivers/iio/adc/ad4691.c:1072:30: sparse:     expected unsigned int [usertype] offload_tx_reset
   drivers/iio/adc/ad4691.c:1072:30: sparse:     got restricted __be32 [usertype]

vim +954 drivers/iio/adc/ad4691.c

   927	
   928	static int ad4691_manual_offload_buffer_postenable(struct iio_dev *indio_dev)
   929	{
   930		struct ad4691_state *st = iio_priv(indio_dev);
   931		struct device *dev = regmap_get_device(st->regmap);
   932		struct spi_device *spi = to_spi_device(dev);
   933		struct spi_offload_trigger_config config = {
   934			.type = SPI_OFFLOAD_TRIGGER_PERIODIC,
   935		};
   936		unsigned int bit, k;
   937		int ret;
   938	
   939		ret = ad4691_enter_conversion_mode(st);
   940		if (ret)
   941			return ret;
   942	
   943		memset(st->offload_xfer, 0, sizeof(st->offload_xfer));
   944	
   945		/*
   946		 * N+1 transfers for N channels. Each CS-low period triggers
   947		 * a conversion AND returns the previous result (pipelined).
   948		 *   TX: [AD4691_ADC_CHAN(n), 0x00, 0x00, 0x00]
   949		 *   RX: [data_hi, data_lo, 0x00, 0x00]   (shift=16)
   950		 * Transfer 0 RX is garbage; transfers 1..N carry real data.
   951		 */
   952		k = 0;
   953		iio_for_each_active_channel(indio_dev, bit) {
 > 954			st->offload_tx_cmd[k] =
   955				cpu_to_be32(FIELD_PREP(AD4691_MSG_ADDR_HI,
   956						       AD4691_ADC_CHAN(bit)));
   957			st->offload_xfer[k].tx_buf = &st->offload_tx_cmd[k];
   958			st->offload_xfer[k].len = sizeof(u32);
   959			st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
   960			st->offload_xfer[k].cs_change = 1;
   961			st->offload_xfer[k].cs_change_delay.value = AD4691_CNV_HIGH_TIME_NS;
   962			st->offload_xfer[k].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
   963			/* First transfer RX is garbage — skip it. */
   964			if (k > 0)
   965				st->offload_xfer[k].offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
   966			k++;
   967		}
   968	
   969		/* Final NOOP to flush pipeline and capture last channel. */
   970		st->offload_tx_cmd[k] =
   971			cpu_to_be32(FIELD_PREP(AD4691_MSG_ADDR_HI, AD4691_NOOP));
   972		st->offload_xfer[k].tx_buf = &st->offload_tx_cmd[k];
   973		st->offload_xfer[k].len = sizeof(u32);
   974		st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
   975		st->offload_xfer[k].offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
   976		k++;
   977	
   978		spi_message_init_with_transfers(&st->offload_msg, st->offload_xfer, k);
   979		st->offload_msg.offload = st->offload;
   980	
   981		ret = spi_optimize_message(spi, &st->offload_msg);
   982		if (ret)
   983			goto err_exit_conversion;
   984	
   985		config.periodic.frequency_hz = st->offload_trigger_hz;
   986		ret = spi_offload_trigger_enable(st->offload, st->offload_trigger, &config);
   987		if (ret)
   988			goto err_unoptimize;
   989	
   990		return 0;
   991	
   992	err_unoptimize:
   993		spi_unoptimize_message(&st->offload_msg);
   994	err_exit_conversion:
   995		ad4691_exit_conversion_mode(st);
   996		return ret;
   997	}
   998	
   999	static int ad4691_manual_offload_buffer_predisable(struct iio_dev *indio_dev)
  1000	{
  1001		struct ad4691_state *st = iio_priv(indio_dev);
  1002	
  1003		spi_offload_trigger_disable(st->offload, st->offload_trigger);
  1004		spi_unoptimize_message(&st->offload_msg);
  1005	
  1006		return ad4691_exit_conversion_mode(st);
  1007	}
  1008	
  1009	static const struct iio_buffer_setup_ops ad4691_manual_offload_buffer_setup_ops = {
  1010		.postenable = &ad4691_manual_offload_buffer_postenable,
  1011		.predisable = &ad4691_manual_offload_buffer_predisable,
  1012	};
  1013	
  1014	static int ad4691_cnv_burst_offload_buffer_postenable(struct iio_dev *indio_dev)
  1015	{
  1016		struct ad4691_state *st = iio_priv(indio_dev);
  1017		struct device *dev = regmap_get_device(st->regmap);
  1018		struct spi_device *spi = to_spi_device(dev);
  1019		struct spi_offload_trigger_config config = {
  1020			.type = SPI_OFFLOAD_TRIGGER_DATA_READY,
  1021		};
  1022		unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);
  1023		unsigned int bit, k;
  1024		int ret;
  1025	
  1026		ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
  1027				   (u16)~(*indio_dev->active_scan_mask));
  1028		if (ret)
  1029			return ret;
  1030	
  1031		ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
  1032				   *indio_dev->active_scan_mask);
  1033		if (ret)
  1034			return ret;
  1035	
  1036		iio_for_each_active_channel(indio_dev, bit) {
  1037			ret = regmap_write(st->regmap, AD4691_ACC_COUNT_LIMIT(bit),
  1038					   AD4691_ACC_COUNT_VAL);
  1039			if (ret)
  1040				return ret;
  1041		}
  1042	
  1043		ret = ad4691_enter_conversion_mode(st);
  1044		if (ret)
  1045			return ret;
  1046	
  1047		memset(st->offload_xfer, 0, sizeof(st->offload_xfer));
  1048	
  1049		/*
  1050		 * N transfers to read N AVG_IN registers plus one state-reset
  1051		 * transfer (no RX) to re-arm DATA_READY.
  1052		 *   TX: [reg_hi | 0x80, reg_lo, 0x00, 0x00]
  1053		 *   RX: [0x00, 0x00, data_hi, data_lo]   (shift=0)
  1054		 */
  1055		k = 0;
  1056		iio_for_each_active_channel(indio_dev, bit) {
  1057			unsigned int reg = AD4691_AVG_IN(bit);
  1058	
  1059			st->offload_tx_cmd[k] =
  1060				cpu_to_be32(((reg >> 8 | 0x80) << 24) |
  1061					    ((reg & 0xFF) << 16));
  1062			st->offload_xfer[k].tx_buf = &st->offload_tx_cmd[k];
  1063			st->offload_xfer[k].len = sizeof(u32);
  1064			st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
  1065			st->offload_xfer[k].offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
  1066			if (k < n_active - 1)
  1067				st->offload_xfer[k].cs_change = 1;
  1068			k++;
  1069		}
  1070	
  1071		/* State reset to re-arm DATA_READY for the next scan. */
> 1072		st->offload_tx_reset =
  1073			cpu_to_be32(((AD4691_STATE_RESET_REG >> 8) << 24) |
  1074				    ((AD4691_STATE_RESET_REG & 0xFF) << 16) |
  1075				    (AD4691_STATE_RESET_ALL << 8));
  1076		st->offload_xfer[k].tx_buf = &st->offload_tx_reset;
  1077		st->offload_xfer[k].len = sizeof(u32);
  1078		st->offload_xfer[k].bits_per_word = AD4691_OFFLOAD_BITS_PER_WORD;
  1079		k++;
  1080	
  1081		spi_message_init_with_transfers(&st->offload_msg, st->offload_xfer, k);
  1082		st->offload_msg.offload = st->offload;
  1083	
  1084		ret = spi_optimize_message(spi, &st->offload_msg);
  1085		if (ret)
  1086			goto err_exit_conversion;
  1087	
  1088		ret = ad4691_sampling_enable(st, true);
  1089		if (ret)
  1090			goto err_unoptimize;
  1091	
  1092		ret = spi_offload_trigger_enable(st->offload, st->offload_trigger, &config);
  1093		if (ret)
  1094			goto err_sampling_disable;
  1095	
  1096		return 0;
  1097	
  1098	err_sampling_disable:
  1099		ad4691_sampling_enable(st, false);
  1100	err_unoptimize:
  1101		spi_unoptimize_message(&st->offload_msg);
  1102	err_exit_conversion:
  1103		ad4691_exit_conversion_mode(st);
  1104		return ret;
  1105	}
  1106	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

[kernel test robot]

Hi Radu,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 11439c4635edd669ae435eec308f4ab8a0804808]

url:    https://github.com/intel-lab-lkp/linux/commits/Radu-Sabau-via-B4-Relay/dt-bindings-iio-adc-add-AD4691-family/20260321-120718
base:   11439c4635edd669ae435eec308f4ab8a0804808
patch link:    https://lore.kernel.org/r/20260320-ad4692-multichannel-sar-adc-driver-v4-4-052c1050507a%40analog.com
patch subject: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support
config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20260323/202603232017.8IO2whBG-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260323/202603232017.8IO2whBG-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603232017.8IO2whBG-lkp@intel.com/

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> WARNING: modpost: module ad4691 uses symbol devm_iio_dmaengine_buffer_setup_with_handle from namespace IIO_DMAENGINE_BUFFER, but does not import it.

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support

[kernel test robot]

Hi Radu,

kernel test robot noticed the following build errors:

[auto build test ERROR on 11439c4635edd669ae435eec308f4ab8a0804808]

url:    https://github.com/intel-lab-lkp/linux/commits/Radu-Sabau-via-B4-Relay/dt-bindings-iio-adc-add-AD4691-family/20260321-120718
base:   11439c4635edd669ae435eec308f4ab8a0804808
patch link:    https://lore.kernel.org/r/20260320-ad4692-multichannel-sar-adc-driver-v4-4-052c1050507a%40analog.com
patch subject: [PATCH v4 4/4] iio: adc: ad4691: add SPI offload support
config: openrisc-randconfig-r063-20260325 (https://download.01.org/0day-ci/archive/20260325/202603251904.qcAGC4cf-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260325/202603251904.qcAGC4cf-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603251904.qcAGC4cf-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: module ad4691 uses symbol devm_iio_dmaengine_buffer_setup_with_handle from namespace IIO_DMAENGINE_BUFFER, but does not import it.

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v4 1/4] dt-bindings: iio: adc: add AD4691 family

[Jonathan Cameron]

On Fri, 20 Mar 2026 13:03:55 +0200
Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org> wrote:

> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add DT bindings for the Analog Devices AD4691 family of multichannel
> SAR ADCs (AD4691, AD4692, AD4693, AD4694).
> 
> The binding describes the hardware connections:
> 
> - Power domains: avdd-supply (required), vio-supply,

Bit odd to call out avdd-supply as required but not vio-supply


> ref-supply or
>   refin-supply (external reference; the REFIN path enables the
>   internal reference buffer), and an optional ldo-in-supply, that if
>   absent, means the on-chip internal LDO will be used.
> 
> - Optional PWM on the CNV pin selects CNV Burst Mode; when absent,
>   Manual Mode is assumed with CNV tied to SPI CS.
> 
> - An optional reset GPIO (reset-gpios) for hardware reset.
> 
> - Up to four GP pins (gp0..gp3) usable as interrupt sources,
>   identified in firmware via interrupt-names "gp0".."gp3".
> 
> - gpio-controller with #gpio-cells = <2> for GP pin GPIO usage.
> 
> - #trigger-source-cells = <1>: one cell selecting the GP pin number
>   (0-3) used as the SPI offload trigger source.
> 
> Two binding examples are provided: CNV Burst Mode with SPI offload
> (DMA data acquisition driven by DATA_READY on a GP pin), and Manual
> Mode for CPU-driven triggered-buffer or single-shot capture.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> ---
>  .../devicetree/bindings/iio/adc/adi,ad4691.yaml    | 173 +++++++++++++++++++++
>  MAINTAINERS                                        |   7 +
>  2 files changed, 180 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4691.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4691.yaml
> new file mode 100644
> index 000000000000..def9f32c78af
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4691.yaml
> @@ -0,0 +1,173 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/adi,ad4691.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD4691 Family Multichannel SAR ADCs
> +
> +maintainers:
> +  - Radu Sabau <radu.sabau@analog.com>
> +
> +description: |
> +  The AD4691 family are high-speed, low-power, multichannel successive
> +  approximation register (SAR) analog-to-digital converters (ADCs) with
> +  an SPI-compatible serial interface. The ADC supports CNV Burst Mode,
> +  where an external PWM drives the CNV pin, and Manual Mode, where CNV
> +  is directly tied to the SPI chip-select.
> +
> +  Datasheets:
> +    * https://www.analog.com/en/products/ad4692.html

Odd ordering.  Put them in numeric order.

> +    * https://www.analog.com/en/products/ad4691.html
> +    * https://www.analog.com/en/products/ad4694.html
> +    * https://www.analog.com/en/products/ad4693.html
> +
> +$ref: /schemas/spi/spi-peripheral-props.yaml#
...

> +
> +  interrupt-names:
> +    description: Names of the interrupt lines, matching the GP pin names.
> +    minItems: 1
> +    maxItems: 4
> +    items:

I think this wants to be an enum.  Generally look for a similar example
and copy it + test the resulting binding with latest version of the
dts-schema.

> +      - const: gp0
> +      - const: gp1
> +      - const: gp2
> +      - const: gp3
> +

Re: [PATCH v4 1/4] dt-bindings: iio: adc: add AD4691 family

[David Lechner]

On 3/20/26 6:03 AM, Radu Sabau via B4 Relay wrote:
> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add DT bindings for the Analog Devices AD4691 family of multichannel
> SAR ADCs (AD4691, AD4692, AD4693, AD4694).
> 

...

> +allOf:
> +  # ref-supply and refin-supply are mutually exclusive, one is required
> +  - oneOf:
> +      - required:
> +          - ref-supply
> +      - required:
> +          - refin-supply
> +
> +  # CNV Burst Mode (pwms present) without SPI offload requires a DRDY interrupt.
> +  # Offload configurations expose '#trigger-source-cells' instead.

This sounds like a current driver limitation, not a wiring limitation.
So doesn't belong in the devicetree.

A driver could use e.g. timer wait for the conversion instead of an interrupt.

> +  - if:
> +      required:
> +        - pwms
> +      not:
> +        required:
> +          - '#trigger-source-cells'
> +    then:
> +      required:
> +        - interrupts
> +

Re: [PATCH v4 2/4] iio: adc: ad4691: add initial driver for AD4691 family

[Jonathan Cameron]

On Fri, 20 Mar 2026 13:03:56 +0200
Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org> wrote:

> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add support for the Analog Devices AD4691 family of high-speed,
> low-power multichannel SAR ADCs: AD4691 (16-ch, 500 kSPS),
> AD4692 (16-ch, 1 MSPS), AD4693 (8-ch, 500 kSPS) and
> AD4694 (8-ch, 1 MSPS).
> 
> The driver implements a custom regmap layer over raw SPI to handle the
> device's mixed 1/2/3/4-byte register widths and uses the standard IIO
> read_raw/write_raw interface for single-channel reads.
> 
> The chip idles in Autonomous Mode so that single-shot read_raw can use
> the internal oscillator without disturbing the hardware configuration.
> 
> Three voltage supply domains are managed: avdd (required), vio, and a
> reference supply on either the REF pin (ref-supply, external buffer)
> or the REFIN pin (refin-supply, uses the on-chip reference buffer;
> REFBUF_EN is set accordingly). Hardware reset is performed via
> the reset controller framework; a software reset through SPI_CONFIG_A
> is used as fallback when no hardware reset is available.
> 
> Accumulator channel masking for single-shot reads uses ACC_MASK_REG via
> an ADDR_DESCENDING SPI write, which covers both mask bytes in a single
> 16-bit transfer.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
Hi Radu,

Just a few minor comments from me.
I'd have tweak them whilst applying but looks like you are doing a v5 anyway
for other comments.

Jonathan


> diff --git a/drivers/iio/adc/ad4691.c b/drivers/iio/adc/ad4691.c
> new file mode 100644
> index 000000000000..5e02eb44ca44
> --- /dev/null
> +++ b/drivers/iio/adc/ad4691.c

> +#define AD4691_CHANNEL(ch)						\
> +	{								\
> +		.type = IIO_VOLTAGE,					\
> +		.indexed = 1,						\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)		\
> +				    | BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
> +		.info_mask_separate_available =				\
> +				      BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
> +		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE),	\
> +		.channel = ch,						\
> +		.scan_index = ch,					\
> +		.scan_type = {						\
> +			.sign = 'u',					\
> +			.realbits = 16,					\
> +			.storagebits = 16,				\
> +			.shift = 0,					\

Unless there is a reason to need the 0 to act as documentation we normally
assume it's the natural default and don't set it explicitly (let the C
struct initialization rules deal with setting it to 0 for us).

> +		},							\
> +	}


> +static int ad4691_set_sampling_freq(struct iio_dev *indio_dev, int freq)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int start = (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1;

Use 1 * HZ_PER_MHZ

May seem pointless but that conversion scale macro on it's own looks
strange with respect to what is it converting.

> +	unsigned int i;
> +
> +	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> +	if (IIO_DEV_ACQUIRE_FAILED(claim))
> +		return -EBUSY;
> +
> +	for (i = start; i < ARRAY_SIZE(ad4691_osc_freqs); i++) {
> +		if ((int)ad4691_osc_freqs[i] == freq)

I would flip this around to reduce the indent of the path for when
we have a match.

		if ((int)ad4691_osc_freqs[i] != freq)
			continue;

		return regmap_update_bits(st->regmap, AD4691_OSC_FREQ_REG,
					  AD4691_OSC_FREQ_MASK, i);


> +			return regmap_update_bits(st->regmap, AD4691_OSC_FREQ_REG,
> +						  AD4691_OSC_FREQ_MASK, i);
> +	}
> +
> +	return -EINVAL;
> +}

> +static int ad4691_single_shot_read(struct iio_dev *indio_dev,
> +				   struct iio_chan_spec const *chan, int *val)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int reg_val;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);
> +
> +	/*
> +	 * Use AUTONOMOUS mode for single-shot reads. The chip always
> +	 * operates in AUTONOMOUS mode in this driver revision.
> +	 */
> +	ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG,
> +			   AD4691_STATE_RESET_ALL);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   BIT(chan->channel));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~BIT(chan->channel));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, AD4691_OSC_FREQ_REG, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_OSC_EN_REG, 1);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Wait for at least 2 internal oscillator periods for the
> +	 * conversion to complete.
> +	 */
> +	fsleep(DIV_ROUND_UP(2 * USEC_PER_SEC,
> +			    ad4691_osc_freqs[FIELD_GET(AD4691_OSC_FREQ_MASK,
> +						       reg_val)]));

Go long on this line for readability.
			    ad4691_osc_freqs[FIELD_GET(AD4691_OSC_FREQ_MASK, reg_val)]));
Is fine.  The whole 80-100 char range is fine to use if it improves redability and
here I think it does.

> +
> +	ret = regmap_write(st->regmap, AD4691_OSC_EN_REG, 0);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, AD4691_AVG_IN(chan->channel), &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	*val = reg_val;
> +
> +	ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG, AD4691_STATE_RESET_ALL);
> +	if (ret)
> +		return ret;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad4691_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int *val,
> +			   int *val2, long info)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW: {
> +		IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> +

I think we should have convention of no blank line here.
The bit above is setting a variable then we are checking it for error.

> +		if (IIO_DEV_ACQUIRE_FAILED(claim))
> +			return -EBUSY;
> +
> +		return ad4691_single_shot_read(indio_dev, chan, val);
> +	}
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		return ad4691_get_sampling_freq(st, val);
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_uV / (MICRO / MILLI);
> +		*val2 = chan->scan_type.realbits;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		return -EINVAL;
> +	}
> +}

> +static int ad4691_regulator_setup(struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	ret = devm_regulator_get_enable(dev, "avdd");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to get and enable AVDD\n");
> +
> +	ret = devm_regulator_get_enable(dev, "ldo-in");
> +	if (ret && ret != -ENODEV)
> +		return dev_err_probe(dev, ret, "Failed to get and enable LDO-IN\n");
> +	st->ldo_en = (ret == -ENODEV);
> +
> +	ret = devm_regulator_get_enable(dev, "vio");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to get and enable VIO\n");

Unless there is an ordering constraint for power supplies, I'd move this up to
just after avdd so the two non optional ones are done together.

> +
> +	st->vref_uV = devm_regulator_get_enable_read_voltage(dev, "ref");
> +	if (st->vref_uV >= 0) {
> +		st->refbuf_en = false;
> +	} else if (st->vref_uV == -ENODEV) {
> +		st->vref_uV = devm_regulator_get_enable_read_voltage(dev, "refin");
> +		st->refbuf_en = true;
> +	}

Re: [PATCH v4 2/4] iio: adc: ad4691: add initial driver for AD4691 family

[Nuno Sá]

Hi Radu,

minor comments on top of what was said already,

On Fri, 2026-03-20 at 13:03 +0200, Radu Sabau via B4 Relay wrote:
> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add support for the Analog Devices AD4691 family of high-speed,
> low-power multichannel SAR ADCs: AD4691 (16-ch, 500 kSPS),
> AD4692 (16-ch, 1 MSPS), AD4693 (8-ch, 500 kSPS) and
> AD4694 (8-ch, 1 MSPS).
> 
> The driver implements a custom regmap layer over raw SPI to handle the
> device's mixed 1/2/3/4-byte register widths and uses the standard IIO
> read_raw/write_raw interface for single-channel reads.
> 
> The chip idles in Autonomous Mode so that single-shot read_raw can use
> the internal oscillator without disturbing the hardware configuration.
> 
> Three voltage supply domains are managed: avdd (required), vio, and a
> reference supply on either the REF pin (ref-supply, external buffer)
> or the REFIN pin (refin-supply, uses the on-chip reference buffer;
> REFBUF_EN is set accordingly). Hardware reset is performed via
> the reset controller framework; a software reset through SPI_CONFIG_A
> is used as fallback when no hardware reset is available.
> 
> Accumulator channel masking for single-shot reads uses ACC_MASK_REG via
> an ADDR_DESCENDING SPI write, which covers both mask bytes in a single
> 16-bit transfer.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> ---
>  MAINTAINERS              |   1 +
>  drivers/iio/adc/Kconfig  |  11 +
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad4691.c | 686 +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 699 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 438ca850fa1c..24e4502b8292 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1490,6 +1490,7 @@ L:	linux-iio@vger.kernel.org
>  S:	Supported
>  W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/adc/adi,ad4691.yaml
> +F:	drivers/iio/adc/ad4691.c
>  

...

> 
> +
> +struct ad4691_state {
> +	const struct ad4691_chip_info	*info;
> +	struct regmap			*regmap;
> +	int				vref_uV;
> +	bool				refbuf_en;
> +	bool				ldo_en;
> +	/*
> +	 * Synchronize access to members of the driver state, and ensure
> +	 * atomicity of consecutive SPI operations.
> +	 */
> +	struct mutex			lock;
> +};

I would not use tabs and align all the members. Makes thinks harder in the future if
an update is needed. I would just use a simple space.

> +
> +static int ad4691_reg_read(void *context, unsigned int reg, unsigned int *val)
> +{
> +	struct spi_device *spi = context;
> +	u8 tx[2], rx[4];
> +	int ret;
> +
> +	put_unaligned_be16(0x8000 | reg, tx);
> +
> +	switch (reg) {
> +	case 0 ... AD4691_OSC_FREQ_REG:
> +	case AD4691_SPARE_CONTROL ... AD4691_ACC_SAT_OVR_REG(15):
> +		ret = spi_write_then_read(spi, tx, 2, rx, 1);
> +		if (ret)
> +			return ret;
> +		*val = rx[0];
> +		return 0;
> +	case AD4691_STD_SEQ_CONFIG:
> +	case AD4691_AVG_IN(0) ... AD4691_AVG_IN(15):
> +		ret = spi_write_then_read(spi, tx, 2, rx, 2);
> +		if (ret)
> +			return ret;
> +		*val = get_unaligned_be16(rx);
> +		return 0;
> +	case AD4691_AVG_STS_IN(0) ... AD4691_AVG_STS_IN(15):
> +	case AD4691_ACC_IN(0) ... AD4691_ACC_IN(15):
> +		ret = spi_write_then_read(spi, tx, 2, rx, 3);
> +		if (ret)
> +			return ret;
> +		*val = get_unaligned_be24(rx);
> +		return 0;
> +	case AD4691_ACC_STS_DATA(0) ... AD4691_ACC_STS_DATA(15):
> +		ret = spi_write_then_read(spi, tx, 2, rx, 4);
> +		if (ret)
> +			return ret;
> +		*val = get_unaligned_be32(rx);
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad4691_reg_write(void *context, unsigned int reg, unsigned int val)
> +{
> +	struct spi_device *spi = context;
> +	u8 tx[4];
> +
> +	put_unaligned_be16(reg, tx);
> +
> +	switch (reg) {
> +	case 0 ... AD4691_OSC_FREQ_REG:
> +	case AD4691_SPARE_CONTROL ... AD4691_ACC_MASK_REG - 1:
> +	case AD4691_ACC_MASK_REG + 1 ... AD4691_GPIO_MODE2_REG:
> +		if (val > 0xFF)
> +			return -EINVAL;
> +		tx[2] = val;
> +		return spi_write_then_read(spi, tx, 3, NULL, 0);
> +	case AD4691_ACC_MASK_REG:
> +	case AD4691_STD_SEQ_CONFIG:
> +		if (val > 0xFFFF)
> +			return -EINVAL;
> +		put_unaligned_be16(val, &tx[2]);
> +		return spi_write_then_read(spi, tx, 4, NULL, 0);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static bool ad4691_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case AD4691_STATUS_REG:
> +	case AD4691_CLAMP_STATUS1_REG:
> +	case AD4691_CLAMP_STATUS2_REG:
> +	case AD4691_GPIO_READ:
> +	case AD4691_ACC_STATUS_FULL1_REG ... AD4691_ACC_STATUS_SAT2_REG:
> +	case AD4691_ACC_SAT_OVR_REG(0) ... AD4691_ACC_SAT_OVR_REG(15):
> +	case AD4691_AVG_IN(0) ... AD4691_AVG_IN(15):
> +	case AD4691_AVG_STS_IN(0) ... AD4691_AVG_STS_IN(15):
> +	case AD4691_ACC_IN(0) ... AD4691_ACC_IN(15):
> +	case AD4691_ACC_STS_DATA(0) ... AD4691_ACC_STS_DATA(15):
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool ad4691_readable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case 0 ... AD4691_OSC_FREQ_REG:
> +	case AD4691_SPARE_CONTROL ... AD4691_ACC_SAT_OVR_REG(15):
> +	case AD4691_STD_SEQ_CONFIG:
> +	case AD4691_AVG_IN(0) ... AD4691_AVG_IN(15):
> +	case AD4691_AVG_STS_IN(0) ... AD4691_AVG_STS_IN(15):
> +	case AD4691_ACC_IN(0) ... AD4691_ACC_IN(15):
> +	case AD4691_ACC_STS_DATA(0) ... AD4691_ACC_STS_DATA(15):
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool ad4691_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case 0 ... AD4691_OSC_FREQ_REG:
> +	case AD4691_STD_SEQ_CONFIG:
> +	case AD4691_SPARE_CONTROL ... AD4691_GPIO_MODE2_REG:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static const struct regmap_config ad4691_regmap_config = {
> +	.reg_bits = 16,
> +	.val_bits = 32,
> +	.reg_read = ad4691_reg_read,
> +	.reg_write = ad4691_reg_write,
> +	.volatile_reg = ad4691_volatile_reg,
> +	.readable_reg = ad4691_readable_reg,
> +	.writeable_reg = ad4691_writeable_reg,
> +	.max_register = AD4691_ACC_STS_DATA(15),
> +	.cache_type = REGCACHE_MAPLE,
> +};
> +
> +static int ad4691_get_sampling_freq(struct ad4691_state *st, int *val)
> +{
> +	unsigned int reg_val;
> +	int ret;
> +
> +	ret = regmap_read(st->regmap, AD4691_OSC_FREQ_REG, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	*val = ad4691_osc_freqs[FIELD_GET(AD4691_OSC_FREQ_MASK, reg_val)];
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad4691_set_sampling_freq(struct iio_dev *indio_dev, int freq)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int start = (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1;
> +	unsigned int i;
> +
> +	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> +	if (IIO_DEV_ACQUIRE_FAILED(claim))
> +		return -EBUSY;
> +
> +	for (i = start; i < ARRAY_SIZE(ad4691_osc_freqs); i++) {
> +		if ((int)ad4691_osc_freqs[i] == freq)

maybe just make the array signed.

> +			return regmap_update_bits(st->regmap, AD4691_OSC_FREQ_REG,
> +						  AD4691_OSC_FREQ_MASK, i);
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad4691_read_avail(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     const int **vals, int *type,
> +			     int *length, long mask)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int start = (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*vals = (const int *)&ad4691_osc_freqs[start];
> +		*type = IIO_VAL_INT;
> +		*length = ARRAY_SIZE(ad4691_osc_freqs) - start;
> +		return IIO_AVAIL_LIST;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad4691_single_shot_read(struct iio_dev *indio_dev,
> +				   struct iio_chan_spec const *chan, int *val)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int reg_val;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);
> +
> +	/*
> +	 * Use AUTONOMOUS mode for single-shot reads. The chip always
> +	 * operates in AUTONOMOUS mode in this driver revision.
> +	 */
> +	ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG,
> +			   AD4691_STATE_RESET_ALL);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   BIT(chan->channel));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~BIT(chan->channel));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, AD4691_OSC_FREQ_REG, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_OSC_EN_REG, 1);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Wait for at least 2 internal oscillator periods for the
> +	 * conversion to complete.
> +	 */
> +	fsleep(DIV_ROUND_UP(2 * USEC_PER_SEC,
> +			    ad4691_osc_freqs[FIELD_GET(AD4691_OSC_FREQ_MASK,
> +						       reg_val)]));
> +
> +	ret = regmap_write(st->regmap, AD4691_OSC_EN_REG, 0);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(st->regmap, AD4691_AVG_IN(chan->channel), &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	*val = reg_val;
> +
> +	ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG, AD4691_STATE_RESET_ALL);
> +	if (ret)
> +		return ret;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad4691_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int *val,
> +			   int *val2, long info)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW: {
> +		IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> +
nit: I would drop the extra new line. The check below is related to the
above.

> +		if (IIO_DEV_ACQUIRE_FAILED(claim))
> +			return -EBUSY;
> +
> +		return ad4691_single_shot_read(indio_dev, chan, val);
> +	}
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		return ad4691_get_sampling_freq(st, val);
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_uV / (MICRO / MILLI);
> +		*val2 = chan->scan_type.realbits;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad4691_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		return ad4691_set_sampling_freq(indio_dev, val);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad4691_reg_access(struct iio_dev *indio_dev, unsigned int reg,
> +			     unsigned int writeval, unsigned int *readval)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +
> +	guard(mutex)(&st->lock);
> +
> +	if (readval)
> +		return regmap_read(st->regmap, reg, readval);
> +
> +	return regmap_write(st->regmap, reg, writeval);
> +}
> +
> +static const struct iio_info ad4691_info = {
> +	.read_raw = &ad4691_read_raw,
> +	.write_raw = &ad4691_write_raw,
> +	.read_avail = &ad4691_read_avail,
> +	.debugfs_reg_access = &ad4691_reg_access,
> +};
> +
> +static int ad4691_regulator_setup(struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	ret = devm_regulator_get_enable(dev, "avdd");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to get and enable AVDD\n");
> +
> +	ret = devm_regulator_get_enable(dev, "ldo-in");
> +	if (ret && ret != -ENODEV)
> +		return dev_err_probe(dev, ret, "Failed to get and enable LDO-IN\n");
> +	st->ldo_en = (ret == -ENODEV);
> +
> +	ret = devm_regulator_get_enable(dev, "vio");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to get and enable VIO\n");
> +
> +	st->vref_uV = devm_regulator_get_enable_read_voltage(dev, "ref");
> +	if (st->vref_uV >= 0) {
> +		st->refbuf_en = false;
> +	} else if (st->vref_uV == -ENODEV) {
> +		st->vref_uV = devm_regulator_get_enable_read_voltage(dev, "refin");
> +		st->refbuf_en = true;
> +	}
> +	if (st->vref_uV < 0)
> +		return dev_err_probe(dev, st->vref_uV,
> +				     "Failed to get reference supply\n");
> +
> +	if (st->vref_uV < AD4691_VREF_uV_MIN || st->vref_uV > AD4691_VREF_uV_MAX)
> +		return dev_err_probe(dev, -EINVAL,
> +				     "vref(%d) must be in the range [%u...%u]\n",
> +				     st->vref_uV, AD4691_VREF_uV_MIN,
> +				     AD4691_VREF_uV_MAX);
> +
> +	return 0;
> +}
> +
> +static int ad4691_reset(struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct reset_control *rst;
> +
> +	rst = devm_reset_control_get_optional_exclusive(dev, NULL);
> +	if (IS_ERR(rst))
> +		return dev_err_probe(dev, PTR_ERR(rst), "Failed to get reset\n");
> +
> +	if (!rst)
> +		/* No hardware reset available, fall back to software reset. */
> +		return regmap_write(st->regmap, AD4691_SPI_CONFIG_A_REG,
> +				    AD4691_SW_RESET);
> +
> +	reset_control_assert(rst);

Can't we ask for the reset in the asserted state already?

> +	/* Reset delay required. See datasheet Table 5. */
> +	fsleep(300);
> +	reset_control_deassert(rst);
> +
> +	return 0;
> +}
> +
> +static int ad4691_config(struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	enum ad4691_ref_ctrl ref_val;
> +	int ret;
> +
> +	switch (st->vref_uV) {
> +	case AD4691_VREF_uV_MIN ... AD4691_VREF_2P5_uV_MAX:
> +		ref_val = AD4691_VREF_2P5;
> +		break;
> +	case AD4691_VREF_2P5_uV_MAX + 1 ... AD4691_VREF_3P0_uV_MAX:
> +		ref_val = AD4691_VREF_3P0;
> +		break;
> +	case AD4691_VREF_3P0_uV_MAX + 1 ... AD4691_VREF_3P3_uV_MAX:
> +		ref_val = AD4691_VREF_3P3;
> +		break;
> +	case AD4691_VREF_3P3_uV_MAX + 1 ... AD4691_VREF_4P096_uV_MAX:
> +		ref_val = AD4691_VREF_4P096;
> +		break;
> +	case AD4691_VREF_4P096_uV_MAX + 1 ... AD4691_VREF_uV_MAX:
> +		ref_val = AD4691_VREF_5P0;
> +		break;
> +	default:
> +		return dev_err_probe(dev, -EINVAL,
> +				     "Unsupported vref voltage: %d uV\n",
> +				     st->vref_uV);
> +	}
> +
> +	ret = regmap_write(st->regmap, AD4691_REF_CTRL,
> +			   FIELD_PREP(AD4691_REF_CTRL_MASK, ref_val) |
> +			   (st->refbuf_en ? AD4691_REFBUF_EN : 0));
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to write REF_CTRL\n");
> +
> +	ret = regmap_write(st->regmap, AD4691_DEVICE_SETUP,
> +			   st->ldo_en ? AD4691_LDO_EN : 0);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to write DEVICE_SETUP\n");
> +
> +	/*
> +	 * Set the internal oscillator to the highest valid rate for this chip.
> +	 * Index 0 (1 MHz) is valid only for AD4692/AD4694; AD4691/AD4693 start
> +	 * at index 1 (500 kHz).
> +	 */
> +	ret = regmap_write(st->regmap, AD4691_OSC_FREQ_REG,
> +			   (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to write OSC_FREQ\n");
> +
> +	/* Device always operates in AUTONOMOUS mode. */

Kind of obvious from the code. Drop the comment please.


- Nuno Sá

Re: [PATCH v4 3/4] iio: adc: ad4691: add triggered buffer support

[Jonathan Cameron]

On Fri, 20 Mar 2026 13:03:57 +0200
Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org> wrote:

> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add buffered capture support using the IIO triggered buffer framework.
> 
> CNV Burst Mode: the GP pin identified by interrupt-names in the device

The first I assume?  Might be up to 4 of them.

> tree is configured as DATA_READY output. The IRQ handler stops
> conversions and fires the IIO trigger; the trigger handler executes a
> pre-built SPI message that reads all active channels from the AVG_IN
> accumulator registers and then resets accumulator state and restarts
> conversions for the next cycle.

No oversampling configuration?  If it's a fixed length burst I'd still
expect to see an indication of what it is and if we can flip back to
no oversampling by changing mode, that should be oversampling == 1.
Seems there is a depth setting for the averaging filters, that superficially
at least appears to be the right control for this.

Seems like there is an SPI burst mode as well?  That feels like very
standard oversampling.

> 
> Manual Mode: CNV is tied to SPI CS so each transfer simultaneously
> reads the previous result and starts the next conversion (pipelined
> N+1 scheme). At preenable time a pre-built, optimised SPI message of
> N+1 transfers is constructed (N channel reads plus one NOOP to drain
> the pipeline). The trigger handler executes the message in a single
> spi_sync() call and collects the results. An external trigger (e.g.
> iio-trig-hrtimer) is required to drive the trigger at the desired
> sample rate.
> 
> Both modes share the same trigger handler and push a complete scan —
> one u16 slot per channel at its scan_index position, followed by a
> timestamp — to the IIO buffer via iio_push_to_buffers_with_ts().
> 
> The CNV Burst Mode sampling frequency (PWM period) is exposed as a
> buffer-level attribute via IIO_DEVICE_ATTR.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
A few comments inline.  All the modes etc in this driver are complex
enough I think this one needs a driver specific document in Documentation/iio

Thanks,

Jonathan

> diff --git a/drivers/iio/adc/ad4691.c b/drivers/iio/adc/ad4691.c
> index 5e02eb44ca44..db776de32846 100644
> --- a/drivers/iio/adc/ad4691.c
> +++ b/drivers/iio/adc/ad4691.c

> @@ -121,6 +140,7 @@ static const struct iio_chan_spec ad4691_channels[] = {
>  	AD4691_CHANNEL(13),
>  	AD4691_CHANNEL(14),
>  	AD4691_CHANNEL(15),
> +	IIO_CHAN_SOFT_TIMESTAMP(16),
>  };
>  
>  static const struct iio_chan_spec ad4693_channels[] = {
> @@ -132,6 +152,7 @@ static const struct iio_chan_spec ad4693_channels[] = {
>  	AD4691_CHANNEL(5),
>  	AD4691_CHANNEL(6),
>  	AD4691_CHANNEL(7),
> +	IIO_CHAN_SOFT_TIMESTAMP(16),

Any big advantage in pushing it all the way down to 16?  It's ABI compliant
as these only have to be monotonic, but I'd feel it was more natural as 8 unless
there is something I'm missing.

>  };
>  
>  /*
> @@ -189,16 +210,63 @@ static const struct ad4691_chip_info ad4694_chip_info = {
>  struct ad4691_state {
>  	const struct ad4691_chip_info	*info;
>  	struct regmap			*regmap;
> +
> +	struct pwm_device		*conv_trigger;
> +	struct iio_trigger		*trig;
> +	int				irq;
> +
> +	bool				manual_mode;
> +
>  	int				vref_uV;
>  	bool				refbuf_en;
>  	bool				ldo_en;
> +	u32				cnv_period_ns;
>  	/*
>  	 * Synchronize access to members of the driver state, and ensure
>  	 * atomicity of consecutive SPI operations.
>  	 */
>  	struct mutex			lock;
> +	/*
> +	 * Per-buffer-enabl ree lifetimesources:
> +	 * Manual Mode - a pre-built SPI message that clocks out N+1
> +	 *		 transfers in one go.
> +	 * CNV Burst Mode - a pre-built SPI message that clocks out 2*N
> +	 *		    transfers in one go.
> +	 */
> +	void				*scan_devm_group;
> +	struct spi_message		scan_msg;
> +	struct spi_transfer		*scan_xfers;
> +	__be16				*scan_tx;
> +	__be16				*scan_rx;
> +	/* Scan buffer: one slot per channel (u16) plus timestamp */
> +	struct {
> +		u16 vals[16];
> +		s64 ts __aligned(8);

aligned_s64

That was introduced last year IIRC.


> +	} scan __aligned(IIO_DMA_MINALIGN);
>  };

>  static int ad4691_reg_read(void *context, unsigned int reg, unsigned int *val)
>  {
>  	struct spi_device *spi = context;
> @@ -341,14 +409,16 @@ static int ad4691_get_sampling_freq(struct ad4691_state *st, int *val)
>  static int ad4691_set_sampling_freq(struct iio_dev *indio_dev, int freq)
>  {
>  	struct ad4691_state *st = iio_priv(indio_dev);
> -	unsigned int start = (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1;
>  	unsigned int i;
>  
> +	if (freq > st->info->max_rate)
> +		return -EINVAL;
> +
>  	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
>  	if (IIO_DEV_ACQUIRE_FAILED(claim))
>  		return -EBUSY;
>  
> -	for (i = start; i < ARRAY_SIZE(ad4691_osc_freqs); i++) {
> +	for (i = 0; i < ARRAY_SIZE(ad4691_osc_freqs); i++) {

Why is the start offset no longer relevant?

>  		if ((int)ad4691_osc_freqs[i] == freq)
>  			return regmap_update_bits(st->regmap, AD4691_OSC_FREQ_REG,
>  						  AD4691_OSC_FREQ_MASK, i);

> @@ -386,8 +459,7 @@ static int ad4691_single_shot_read(struct iio_dev *indio_dev,
>  	guard(mutex)(&st->lock);
>  
>  	/*
> -	 * Use AUTONOMOUS mode for single-shot reads. The chip always
> -	 * operates in AUTONOMOUS mode in this driver revision.
> +	 * Use AUTONOMOUS mode for single-shot reads.
This edit doesn't seem to belong in this patch. I'd just put the new
text in place in the earlier patch.

> +static int ad4691_manual_buffer_preenable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct spi_device *spi = to_spi_device(dev);
> +	unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);
> +	unsigned int n_xfers = n_active + 1;
> +	unsigned int k, i;
> +	int ret;
> +
> +	st->scan_devm_group = devres_open_group(dev, NULL, GFP_KERNEL);
> +	if (!st->scan_devm_group)
> +		return -ENOMEM;
> +
> +	st->scan_xfers = devm_kcalloc(dev, n_xfers, sizeof(*st->scan_xfers),
> +				      GFP_KERNEL);
> +	st->scan_tx = devm_kcalloc(dev, n_xfers, sizeof(*st->scan_tx),
> +				   GFP_KERNEL);
> +	st->scan_rx = devm_kcalloc(dev, n_xfers, sizeof(*st->scan_rx),
> +				   GFP_KERNEL);
> +	if (!st->scan_xfers || !st->scan_tx || !st->scan_rx) {
> +		devres_release_group(dev, st->scan_devm_group);
> +		return -ENOMEM;
> +	}
> +
> +	spi_message_init(&st->scan_msg);
> +
> +	k = 0;
> +	iio_for_each_active_channel(indio_dev, i) {
> +		st->scan_tx[k] = cpu_to_be16(AD4691_ADC_CHAN(i));
> +		st->scan_xfers[k].tx_buf = &st->scan_tx[k];
> +		st->scan_xfers[k].rx_buf = &st->scan_rx[k];
> +		st->scan_xfers[k].len = sizeof(__be16);
> +		st->scan_xfers[k].cs_change = 1;
> +		spi_message_add_tail(&st->scan_xfers[k], &st->scan_msg);
> +		k++;
> +	}
> +
> +	/* Final NOOP transfer to retrieve last channel's result. */
> +	st->scan_tx[k] = cpu_to_be16(AD4691_NOOP);
> +	st->scan_xfers[k].tx_buf = &st->scan_tx[k];
> +	st->scan_xfers[k].rx_buf = &st->scan_rx[k];
> +	st->scan_xfers[k].len = sizeof(__be16);
> +	spi_message_add_tail(&st->scan_xfers[k], &st->scan_msg);
> +
> +	devres_close_group(dev, st->scan_devm_group);

Similar comment to below on devres groups not really being appropriate
here.

> +
> +	st->scan_msg.spi = spi;
> +
> +	ret = spi_optimize_message(spi, &st->scan_msg);
> +	if (ret) {
> +		devres_release_group(dev, st->scan_devm_group);
If you were keeping this, better to do an error handling block via
gotos like you do for the other similar code.

> +		return ret;
> +	}
> +
> +	ret = ad4691_enter_conversion_mode(st);
> +	if (ret) {
> +		spi_unoptimize_message(&st->scan_msg);
> +		devres_release_group(dev, st->scan_devm_group);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ad4691_manual_buffer_postdisable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	ret = ad4691_exit_conversion_mode(st);
> +	spi_unoptimize_message(&st->scan_msg);
> +	devres_release_group(dev, st->scan_devm_group);
> +	return ret;
> +}
;
> +
> +static int ad4691_cnv_burst_buffer_preenable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct spi_device *spi = to_spi_device(dev);
> +	unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);
> +	unsigned int bit, k, i;
> +	int ret;
> +
> +	st->scan_devm_group = devres_open_group(dev, NULL, GFP_KERNEL);
> +	if (!st->scan_devm_group)
> +		return -ENOMEM;
> +
> +	st->scan_xfers = devm_kcalloc(dev, 2 * n_active, sizeof(*st->scan_xfers),
> +				      GFP_KERNEL);

See later.  I don't see a benefit in using a devres group here. It's nothing
to do with device lifetime.

> +	st->scan_tx = devm_kcalloc(dev, n_active, sizeof(*st->scan_tx),
> +				   GFP_KERNEL);
> +	st->scan_rx = devm_kcalloc(dev, n_active, sizeof(*st->scan_rx),
> +				   GFP_KERNEL);
> +	if (!st->scan_xfers || !st->scan_tx || !st->scan_rx) {
> +		devres_release_group(dev, st->scan_devm_group);
> +		return -ENOMEM;
> +	}
> +
> +	spi_message_init(&st->scan_msg);
> +
> +	/*
> +	 * Each AVG_IN read needs two transfers: a 2-byte address write phase
> +	 * followed by a 2-byte data read phase. CS toggles between channels
> +	 * (cs_change=1 on the read phase of all but the last channel).
> +	 */
> +	k = 0;
> +	iio_for_each_active_channel(indio_dev, i) {
> +		st->scan_tx[k] = cpu_to_be16(0x8000 | AD4691_AVG_IN(i));
> +		st->scan_xfers[2 * k].tx_buf = &st->scan_tx[k];
> +		st->scan_xfers[2 * k].len = sizeof(__be16);
> +		spi_message_add_tail(&st->scan_xfers[2 * k], &st->scan_msg);
> +		st->scan_xfers[2 * k + 1].rx_buf = &st->scan_rx[k];
> +		st->scan_xfers[2 * k + 1].len = sizeof(__be16);
> +		if (k < n_active - 1)
> +			st->scan_xfers[2 * k + 1].cs_change = 1;
> +		spi_message_add_tail(&st->scan_xfers[2 * k + 1], &st->scan_msg);
> +		k++;
> +	}
> +
> +	devres_close_group(dev, st->scan_devm_group);

If you were keeping this (against comment below) why close it here?  Close it once
devm calls are done above.

> +
> +	st->scan_msg.spi = spi;
> +
> +	ret = spi_optimize_message(spi, &st->scan_msg);
> +	if (ret) {
> +		devres_release_group(dev, st->scan_devm_group);
> +		return ret;
> +	}
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~(*indio_dev->active_scan_mask));
> +	if (ret)
> +		goto err;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   *indio_dev->active_scan_mask);
> +	if (ret)
> +		goto err;
> +
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		ret = regmap_write(st->regmap, AD4691_ACC_COUNT_LIMIT(bit),
> +				   AD4691_ACC_COUNT_VAL);
> +		if (ret)
> +			goto err;
> +	}
> +
> +	ret = ad4691_enter_conversion_mode(st);
> +	if (ret)
> +		goto err;
> +
> +	ret = ad4691_sampling_enable(st, true);
> +	if (ret)
> +		goto err;
> +
> +	enable_irq(st->irq);
> +	return 0;
> +err:
> +	spi_unoptimize_message(&st->scan_msg);
> +	devres_release_group(dev, st->scan_devm_group);
> +	return ret;
> +}
> +
> +static int ad4691_cnv_burst_buffer_postdisable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	disable_irq(st->irq);
> +
> +	ret = ad4691_sampling_enable(st, false);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   AD4691_SEQ_ALL_CHANNELS_OFF);
> +	if (ret)
> +		return ret;
> +
> +	ret = ad4691_exit_conversion_mode(st);
> +	spi_unoptimize_message(&st->scan_msg);
> +	devres_release_group(dev, st->scan_devm_group);

I'm not seeing an obvious reason for devres group handling here.
Normally we do that if there is a path to remove() in which the cleanup
still needs to be done.  Here there isn't as we always turn the buffer
off earlier in the remove flow.  So I'd do things the old fashioned way
and free them by hand.


> +	return ret;
> +}

> +static IIO_DEVICE_ATTR(sampling_frequency, 0644,
> +		       sampling_frequency_show,
> +		       sampling_frequency_store, 0);
> +
> +static const struct iio_dev_attr *ad4691_buffer_attrs[] = {
> +	&iio_dev_attr_sampling_frequency,
> +	NULL,

No comma.

> +};

> +
> +static irqreturn_t ad4691_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int i, k = 0;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);

General rule (see cleanup.h comments) is don't use guard() or __free()
stuff in a function that also does goto.  Just handle the mutex()
the old fashioned way.  Alternative is to use a helper function and
just leave the iio_trigger_notify_done() in this outer call.

> +
> +	ret = spi_sync(st->scan_msg.spi, &st->scan_msg);
> +	if (ret)
> +		goto done;
> +
> +	if (st->manual_mode) {
> +		iio_for_each_active_channel(indio_dev, i) {
> +			st->scan.vals[i] = be16_to_cpu(st->scan_rx[k + 1]);
> +			k++;
> +		}
> +	} else {
> +		iio_for_each_active_channel(indio_dev, i) {
> +			st->scan.vals[i] = be16_to_cpu(st->scan_rx[k]);
> +			k++;
> +		}
> +
> +		ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG,
> +				   AD4691_STATE_RESET_ALL);
> +		if (ret)
> +			goto done;
> +
> +		ret = ad4691_sampling_enable(st, true);
> +		if (ret)
> +			goto done;
> +	}
> +
> +	iio_push_to_buffers_with_ts(indio_dev, &st->scan, sizeof(st->scan),
> +				    pf->timestamp);
> +
> +done:
> +	iio_trigger_notify_done(indio_dev->trig);
> +	return IRQ_HANDLED;
> +}
> +


> @@ -595,17 +1071,91 @@ static int ad4691_config(struct ad4691_state *st)
>  		return dev_err_probe(dev, ret, "Failed to write DEVICE_SETUP\n");
>  
>  	/*
> -	 * Set the internal oscillator to the highest valid rate for this chip.
> -	 * Index 0 (1 MHz) is valid only for AD4692/AD4694; AD4691/AD4693 start
> -	 * at index 1 (500 kHz).
> +	 * Set the internal oscillator to the highest rate this chip supports.

This reword doesn't obviously fit in this patch. Move it to earlier one.

> +	 * Index 0 (1 MHz) exceeds the 500 kHz max of AD4691/AD4693, so those
> +	 * chips start at index 1 (500 kHz).
>  	 */
>  	ret = regmap_write(st->regmap, AD4691_OSC_FREQ_REG,
> -			   (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1);
> +			   (ad4691_osc_freqs[0] > st->info->max_rate) ? 1 : 0);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "Failed to write OSC_FREQ\n");
>  
>  	/* Device always operates in AUTONOMOUS mode. */
> -	return regmap_write(st->regmap, AD4691_ADC_SETUP, AD4691_AUTONOMOUS_MODE_VAL);
> +	ret = regmap_write(st->regmap, AD4691_ADC_SETUP, AD4691_AUTONOMOUS_MODE);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to write ADC_SETUp\n");
> +
> +	if (st->manual_mode)
> +		return 0;
> +
> +	ret = device_property_read_string_array(dev, "interrupt-names",
> +						&irq_name, 1);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to read interrupt-names\n");
> +
> +	if (strncmp(irq_name, "gp", 2) != 0 ||
> +	    kstrtouint(irq_name + 2, 10, &gp_num) || gp_num > 3)

No need to check this. Just request the individual GPIOs when needed by name.

> +		return dev_err_probe(dev, -EINVAL,
> +				     "Invalid interrupt name '%s'\n", irq_name);
> +
> +	return ad4691_gpio_setup(st, gp_num);
> +}
> +
> +static int ad4691_setup_triggered_buffer(struct iio_dev *indio_dev,
> +					 struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int irq, ret;
> +
> +	st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d",
> +					  indio_dev->name,
> +					  iio_device_id(indio_dev));
> +	if (!st->trig)
> +		return -ENOMEM;
> +
> +	st->trig->ops = &ad4691_trigger_ops;
> +	iio_trigger_set_drvdata(st->trig, st);
> +
> +	ret = devm_iio_trigger_register(dev, st->trig);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "IIO trigger register failed\n");
> +
> +	indio_dev->trig = iio_trigger_get(st->trig);
> +
> +	if (!st->manual_mode) {
> +		/*
> +		 * GP0 asserts at end-of-conversion. The IRQ handler stops
> +		 * conversions and fires the IIO trigger so the trigger handler
> +		 * can read and push the sample to the buffer. The IRQ is kept
> +		 * disabled until the buffer is enabled.
> +		 */
> +		irq = fwnode_irq_get(dev_fwnode(dev), 0);

Given the presence of interrupt names, there is no guarantee that this is GP0.
You need to get it by name to know that.  They can come in any order, or indeed
any given one can be not wired.

> +		if (irq < 0)
> +			return dev_err_probe(dev, irq,
> +					     "failed to get GP interrupt\n");
> +
> +		st->irq = irq;
> +
> +		ret = devm_request_threaded_irq(dev, irq, NULL,
> +						&ad4691_irq,
> +						IRQF_ONESHOT | IRQF_NO_AUTOEN,

When we are not enabling at boot it is usually helpful to add a comment for why
not.

> +						indio_dev->name, indio_dev);
> +		if (ret)
> +			return ret;
> +
> +		return devm_iio_triggered_buffer_setup_ext(dev, indio_dev,
> +							   &iio_pollfunc_store_time,
> +							   &ad4691_trigger_handler,
> +							   IIO_BUFFER_DIRECTION_IN,
> +							   &ad4691_cnv_burst_buffer_setup_ops,
> +							   ad4691_buffer_attrs);
> +	}
> +
> +	return devm_iio_triggered_buffer_setup(dev, indio_dev,
> +					       &iio_pollfunc_store_time,
> +					       &ad4691_trigger_handler,
> +					       &ad4691_manual_buffer_setup_ops);
>  }

RE: [PATCH v4 3/4] iio: adc: ad4691: add triggered buffer support

[Sabau, Radu bogdan]

> -----Original Message-----
> From: Jonathan Cameron <jic23@kernel.org>
> Sent: Saturday, March 21, 2026 5:17 PM
> To: Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org>
> 
> [External]
> 
> On Fri, 20 Mar 2026 13:03:57 +0200
> Radu Sabau via B4 Relay <devnull+radu.sabau.analog.com@kernel.org>
> wrote:
> 
> > From: Radu Sabau <radu.sabau@analog.com>
> >

...

> > tree is configured as DATA_READY output. The IRQ handler stops
> > conversions and fires the IIO trigger; the trigger handler executes a
> > pre-built SPI message that reads all active channels from the AVG_IN
> > accumulator registers and then resets accumulator state and restarts
> > conversions for the next cycle.
> 
> No oversampling configuration?  If it's a fixed length burst I'd still
> expect to see an indication of what it is and if we can flip back to
> no oversampling by changing mode, that should be oversampling == 1.
> Seems there is a depth setting for the averaging filters, that superficially
> at least appears to be the right control for this.
> 
> Seems like there is an SPI burst mode as well?  That feels like very
> standard oversampling.
> 

Hi Jonathan,

You are right! Those depth registers which I wrongly name ACC_COUNT_LIMIT
still (name changed upon chip's release,  I will fix in the next version of the driver)
indeed work as expected.

I verified this using a Logic Analyzer on the SPI signals and GP interrupt to verify
the timing -> GP falls after a longer time if depth is increased -> oversampling is used.

Since this would be a nice addition, I will implement this then in the
next version.

Thank you for this!
Radu

> >
> > Manual Mode: CNV is tied to SPI CS so each transfer simultaneously
> > reads the previous result and starts the next conversion (pipelined
> > N+1 scheme). At preenable time a pre-built, optimised SPI message of
> > N+1 transfers is constructed (N channel reads plus one NOOP to drain
> > the pipeline). The trigger handler executes the message in a single
> > spi_sync() call and collects the results. An external trigger (e.g.
> > iio-trig-hrtimer) is required to drive the trigger at the desired
> > sample rate.
> >

Re: [PATCH v4 3/4] iio: adc: ad4691: add triggered buffer support

[Nuno Sá]

Hi Radu,

Some comments from me.

On Fri, 2026-03-20 at 13:03 +0200, Radu Sabau via B4 Relay wrote:
> From: Radu Sabau <radu.sabau@analog.com>
> 
> Add buffered capture support using the IIO triggered buffer framework.
> 
> CNV Burst Mode: the GP pin identified by interrupt-names in the device
> tree is configured as DATA_READY output. The IRQ handler stops
> conversions and fires the IIO trigger; the trigger handler executes a
> pre-built SPI message that reads all active channels from the AVG_IN
> accumulator registers and then resets accumulator state and restarts
> conversions for the next cycle.
> 
> Manual Mode: CNV is tied to SPI CS so each transfer simultaneously
> reads the previous result and starts the next conversion (pipelined
> N+1 scheme). At preenable time a pre-built, optimised SPI message of
> N+1 transfers is constructed (N channel reads plus one NOOP to drain
> the pipeline). The trigger handler executes the message in a single
> spi_sync() call and collects the results. An external trigger (e.g.
> iio-trig-hrtimer) is required to drive the trigger at the desired
> sample rate.
> 
> Both modes share the same trigger handler and push a complete scan —
> one u16 slot per channel at its scan_index position, followed by a
> timestamp — to the IIO buffer via iio_push_to_buffers_with_ts().
> 
> The CNV Burst Mode sampling frequency (PWM period) is exposed as a
> buffer-level attribute via IIO_DEVICE_ATTR.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> ---
>  drivers/iio/adc/Kconfig  |   2 +
>  drivers/iio/adc/ad4691.c | 584 +++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 571 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 3685a03aa8dc..d498f16c0816 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -142,6 +142,8 @@ config AD4170_4
>  config AD4691
>  	tristate "Analog Devices AD4691 Family ADC Driver"
>  	depends on SPI
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
>  	select REGMAP
>  	help
>  	  Say yes here to build support for Analog Devices AD4691 Family MuxSAR
> diff --git a/drivers/iio/adc/ad4691.c b/drivers/iio/adc/ad4691.c
> index 5e02eb44ca44..db776de32846 100644
> --- a/drivers/iio/adc/ad4691.c
> +++ b/drivers/iio/adc/ad4691.c
> @@ -9,9 +9,12 @@
>  #include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/err.h>
> +#include <linux/interrupt.h>
>  #include <linux/math.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
> +#include <linux/property.h>
> +#include <linux/pwm.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/reset.h>
> @@ -19,7 +22,12 @@
>  #include <linux/units.h>
>  #include <linux/unaligned.h>
>  
> +#include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
>  
>  #define AD4691_VREF_uV_MIN			2400000
>  #define AD4691_VREF_uV_MAX			5250000
> @@ -28,6 +36,8 @@
>  #define AD4691_VREF_3P3_uV_MAX			3750000
>  #define AD4691_VREF_4P096_uV_MAX		4500000
>  
> +#define AD4691_CNV_DUTY_CYCLE_NS		380
> +
>  #define AD4691_SPI_CONFIG_A_REG			0x000
>  #define AD4691_SW_RESET				(BIT(7) | BIT(0))
>  

...

> 
> +static int ad4691_cnv_burst_buffer_preenable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	struct spi_device *spi = to_spi_device(dev);
> +	unsigned int n_active = hweight_long(*indio_dev->active_scan_mask);
> +	unsigned int bit, k, i;
> +	int ret;
> +
> +	st->scan_devm_group = devres_open_group(dev, NULL, GFP_KERNEL);
> +	if (!st->scan_devm_group)
> +		return -ENOMEM;

Agree with Jonathan. Not seeing a valid reason for the above.

> +
> +	st->scan_xfers = devm_kcalloc(dev, 2 * n_active, sizeof(*st->scan_xfers),
> +				      GFP_KERNEL);
> +	st->scan_tx = devm_kcalloc(dev, n_active, sizeof(*st->scan_tx),
> +				   GFP_KERNEL);
> +	st->scan_rx = devm_kcalloc(dev, n_active, sizeof(*st->scan_rx),
> +				   GFP_KERNEL);
> +	if (!st->scan_xfers || !st->scan_tx || !st->scan_rx) {
> +		devres_release_group(dev, st->scan_devm_group);
> +		return -ENOMEM;
> +	}
> +
> +	spi_message_init(&st->scan_msg);
> +
> +	/*
> +	 * Each AVG_IN read needs two transfers: a 2-byte address write phase
> +	 * followed by a 2-byte data read phase. CS toggles between channels
> +	 * (cs_change=1 on the read phase of all but the last channel).
> +	 */
> +	k = 0;
> +	iio_for_each_active_channel(indio_dev, i) {
> +		st->scan_tx[k] = cpu_to_be16(0x8000 | AD4691_AVG_IN(i));
> +		st->scan_xfers[2 * k].tx_buf = &st->scan_tx[k];
> +		st->scan_xfers[2 * k].len = sizeof(__be16);
> +		spi_message_add_tail(&st->scan_xfers[2 * k], &st->scan_msg);
> +		st->scan_xfers[2 * k + 1].rx_buf = &st->scan_rx[k];
> +		st->scan_xfers[2 * k + 1].len = sizeof(__be16);
> +		if (k < n_active - 1)
> +			st->scan_xfers[2 * k + 1].cs_change = 1;
> +		spi_message_add_tail(&st->scan_xfers[2 * k + 1], &st->scan_msg);
> +		k++;
> +	}
> +
> +	devres_close_group(dev, st->scan_devm_group);
> +
> +	st->scan_msg.spi = spi;
> +
> +	ret = spi_optimize_message(spi, &st->scan_msg);
> +	if (ret) {
> +		devres_release_group(dev, st->scan_devm_group);
> +		return ret;
> +	}
> +
> +	ret = regmap_write(st->regmap, AD4691_ACC_MASK_REG,
> +			   (u16)~(*indio_dev->active_scan_mask));
> +	if (ret)
> +		goto err;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   *indio_dev->active_scan_mask);
> +	if (ret)
> +		goto err;
> +
> +	iio_for_each_active_channel(indio_dev, bit) {
> +		ret = regmap_write(st->regmap, AD4691_ACC_COUNT_LIMIT(bit),
> +				   AD4691_ACC_COUNT_VAL);
> +		if (ret)
> +			goto err;
> +	}
> +
> +	ret = ad4691_enter_conversion_mode(st);
> +	if (ret)
> +		goto err;
> +
> +	ret = ad4691_sampling_enable(st, true);
> +	if (ret)
> +		goto err;
> +
> +	enable_irq(st->irq);
> +	return 0;
> +err:
> +	spi_unoptimize_message(&st->scan_msg);
> +	devres_release_group(dev, st->scan_devm_group);
> +	return ret;
> +}
> +
> +static int ad4691_cnv_burst_buffer_postdisable(struct iio_dev *indio_dev)
> +{
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	disable_irq(st->irq);

Should we use disable_irq_sync()?
> +
> +	ret = ad4691_sampling_enable(st, false);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, AD4691_STD_SEQ_CONFIG,
> +			   AD4691_SEQ_ALL_CHANNELS_OFF);
> +	if (ret)
> +		return ret;
> +
> +	ret = ad4691_exit_conversion_mode(st);
> +	spi_unoptimize_message(&st->scan_msg);
> +	devres_release_group(dev, st->scan_devm_group);
> +	return ret;
> +}
> +
> +static const struct iio_buffer_setup_ops ad4691_cnv_burst_buffer_setup_ops = {
> +	.preenable = &ad4691_cnv_burst_buffer_preenable,
> +	.postdisable = &ad4691_cnv_burst_buffer_postdisable,
> +};
> +
> +static ssize_t sampling_frequency_show(struct device *dev,
> +					struct device_attribute *attr,
> +					char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +
> +	if (st->manual_mode)
> +		return -ENODEV;

Can the above happen at all? I think you're making sure (at probe) this interface
never get's exposed in manual mode.

> +
> +	return sysfs_emit(buf, "%u\n", (u32)(NSEC_PER_SEC / st->cnv_period_ns));
> +}
> +
> +static ssize_t sampling_frequency_store(struct device *dev,
> +					 struct device_attribute *attr,
> +					 const char *buf, size_t len)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	int freq, ret;
> +
> +	if (st->manual_mode)
> +		return -ENODEV;
> +
> +	ret = kstrtoint(buf, 10, &freq);
> +	if (ret)
> +		return ret;
> +
> +	guard(mutex)(&st->lock);
> +
> +	ret = ad4691_set_pwm_freq(st, freq);
> +	if (ret)
> +		return ret;
> +
> +	return len;
> +}
> +
> +static IIO_DEVICE_ATTR(sampling_frequency, 0644,
> +		       sampling_frequency_show,
> +		       sampling_frequency_store, 0);
> +
> +static const struct iio_dev_attr *ad4691_buffer_attrs[] = {
> +	&iio_dev_attr_sampling_frequency,
> +	NULL,
> +};
> +
> +static irqreturn_t ad4691_irq(int irq, void *private)
> +{
> +	struct iio_dev *indio_dev = private;
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +
> +	/*
> +	 * GPx has asserted: stop conversions before reading so the
> +	 * accumulator does not continue sampling while the trigger handler
> +	 * processes the data. Then fire the IIO trigger to push the sample
> +	 * to the buffer.
> +	 */
> +	ad4691_sampling_enable(st, false);
> +	iio_trigger_poll(st->trig);

Not sure you need to save trig in your struct. We already have it in indio_dev->trig. Sure,
it is a private member but still fairly common to see (this patch included):

indio_dev->trig = iio_trigger_get(trig);

So I would say we either assume it's public or start to not allow the above
pattern.

Alternatively, I don't think you're using indio_dev driverdata right? Could save it
in there.

> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct iio_trigger_ops ad4691_trigger_ops = {
> +	.validate_device = iio_trigger_validate_own_device,
> +};
> +
> +static irqreturn_t ad4691_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct ad4691_state *st = iio_priv(indio_dev);
> +	unsigned int i, k = 0;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);
> +
> +	ret = spi_sync(st->scan_msg.spi, &st->scan_msg);
> +	if (ret)
> +		goto done;
> +
> +	if (st->manual_mode) {
> +		iio_for_each_active_channel(indio_dev, i) {
> +			st->scan.vals[i] = be16_to_cpu(st->scan_rx[k + 1]);
> +			k++;
> +		}
> +	} else {
> +		iio_for_each_active_channel(indio_dev, i) {
> +			st->scan.vals[i] = be16_to_cpu(st->scan_rx[k]);
> +			k++;
> +		}
> +
> +		ret = regmap_write(st->regmap, AD4691_STATE_RESET_REG,
> +				   AD4691_STATE_RESET_ALL);
> +		if (ret)
> +			goto done;
> +
> +		ret = ad4691_sampling_enable(st, true);
> +		if (ret)
> +			goto done;
> +	}
> +
> +	iio_push_to_buffers_with_ts(indio_dev, &st->scan, sizeof(st->scan),
> +				    pf->timestamp);
> +
> +done:
> +	iio_trigger_notify_done(indio_dev->trig);
> +	return IRQ_HANDLED;
> +}
> +
>  static const struct iio_info ad4691_info = {
>  	.read_raw = &ad4691_read_raw,
>  	.write_raw = &ad4691_write_raw,
> @@ -495,6 +934,25 @@ static const struct iio_info ad4691_info = {
>  	.debugfs_reg_access = &ad4691_reg_access,
>  };
>  
> +static int ad4691_pwm_setup(struct ad4691_state *st)
> +{
> +	struct device *dev = regmap_get_device(st->regmap);
> +	int ret;
> +
> +	st->conv_trigger = devm_pwm_get(dev, "cnv");
> +	if (IS_ERR(st->conv_trigger))
> +		return dev_err_probe(dev, PTR_ERR(st->conv_trigger),
> +				     "Failed to get cnv pwm\n");
> +
> +	ret = devm_add_action_or_reset(dev, ad4691_disable_pwm,
> +				       st->conv_trigger);

This is a suspicious pattern. But I do see it's used like this in more places and it's a no-op
if PWM is already disabled. Still, not sure if agree with this kind "unbalanced" handling.

> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to register PWM disable action\n");
> +
> +	return ad4691_set_pwm_freq(st, st->info->max_rate);
> +}
> +
>  static int ad4691_regulator_setup(struct ad4691_state *st)
>  {
>  	struct device *dev = regmap_get_device(st->regmap);
> @@ -555,12 +1013,30 @@ static int ad4691_reset(struct ad4691_state *st)
>  	return 0;
>  }
>  
> -static int ad4691_config(struct ad4691_state *st)
> +static int ad4691_config(struct ad4691_state *st, u32 max_speed_hz)

My eyes might be failing me but where is 'max_speed_hz' used?


>  {
>  	struct device *dev = regmap_get_device(st->regmap);
>  	enum ad4691_ref_ctrl ref_val;
> +	const char *irq_name;
> +	unsigned int gp_num;
>  	int ret;
>  
> +	/*
> +	 * Determine buffer conversion mode from DT: if a PWM is provided it
> +	 * drives the CNV pin (CNV_BURST_MODE); otherwise CNV is tied to CS
> +	 * and each SPI transfer triggers a conversion (MANUAL_MODE).
> +	 * Both modes idle in AUTONOMOUS mode so that read_raw can use the
> +	 * internal oscillator without disturbing the hardware configuration.
> +	 */
> +	if (device_property_present(dev, "pwms")) {
> +		st->manual_mode = false;
> +		ret = ad4691_pwm_setup(st);
> +		if (ret)
> +			return ret;
> +	} else {
> +		st->manual_mode = true;
> +	}
> +
>  	switch (st->vref_uV) {
>  	case AD4691_VREF_uV_MIN ... AD4691_VREF_2P5_uV_MAX:
>  		ref_val = AD4691_VREF_2P5;
> @@ -595,17 +1071,91 @@ static int ad4691_config(struct ad4691_state *st)
>  		return dev_err_probe(dev, ret, "Failed to write DEVICE_SETUP\n");
>  
>  	/*
> -	 * Set the internal oscillator to the highest valid rate for this chip.
> -	 * Index 0 (1 MHz) is valid only for AD4692/AD4694; AD4691/AD4693 start
> -	 * at index 1 (500 kHz).
> +	 * Set the internal oscillator to the highest rate this chip supports.
> +	 * Index 0 (1 MHz) exceeds the 500 kHz max of AD4691/AD4693, so those
> +	 * chips start at index 1 (500 kHz).
>  	 */
>  	ret = regmap_write(st->regmap, AD4691_OSC_FREQ_REG,
> -			   (st->info->max_rate == HZ_PER_MHZ) ? 0 : 1);
> +			   (ad4691_osc_freqs[0] > st->info->max_rate) ? 1 : 0);

Does this belong to this commit?

>  	if (ret)
>  		return dev_err_probe(dev, ret, "Failed to write OSC_FREQ\n");
>  
>  	/* Device always operates in AUTONOMOUS mode. */
> -	return regmap_write(st->regmap, AD4691_ADC_SETUP, AD4691_AUTONOMOUS_MODE_VAL);
> +	ret = regmap_write(st->regmap, AD4691_ADC_SETUP, AD4691_AUTONOMOUS_MODE);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to write ADC_SETUp\n");
> +
> +	if (st->manual_mode)
> +		return 0;
> +
> +	ret = device_property_read_string_array(dev, "interrupt-names",
> +						&irq_name, 1);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to read interrupt-names\n");
> +
> +	if (strncmp(irq_name, "gp", 2) != 0 ||
> +	    kstrtouint(irq_name + 2, 10, &gp_num) || gp_num > 3)
> +		return dev_err_probe(dev, -EINVAL,
> +				     "Invalid interrupt name '%s'\n", irq_name);
> +

I would likely prefer something like [1] rather than the string parsing.

[1]: https://elixir.bootlin.com/linux/v7.0-rc5/source/drivers/iio/imu/adis16480.c#L1582

- Nuno Sá

RE: [PATCH v4 3/4] iio: adc: ad4691: add triggered buffer support

[Sabau, Radu bogdan]

> -----Original Message-----
> From: Nuno Sá <noname.nuno@gmail.com>
> Sent: Tuesday, March 24, 2026 2:23 PM

...

> > +static int ad4691_cnv_burst_buffer_postdisable(struct iio_dev *indio_dev)
> > +{
> > +	struct ad4691_state *st = iio_priv(indio_dev);
> > +	struct device *dev = regmap_get_device(st->regmap);
> > +	int ret;
> > +
> > +	disable_irq(st->irq);
> 
> Should we use disable_irq_sync()?

Isn't disable_irq() already calling synchronize_irq() inside it? I can't see
disable_irq_sync() in the current kernel, only disable_irq_nosync().

> > +
> > +	ret = ad4691_sampling_enable(st, false);
> > +	if (ret)
> > +		return ret;
> > +

Re: [PATCH v4 3/4] iio: adc: ad4691: add triggered buffer support

[Nuno Sá]

On Wed, 2026-03-25 at 12:47 +0000, Sabau, Radu bogdan wrote:
> 
> 
> > -----Original Message-----
> > From: Nuno Sá <noname.nuno@gmail.com>
> > Sent: Tuesday, March 24, 2026 2:23 PM
> 
> ...
> 
> > > +static int ad4691_cnv_burst_buffer_postdisable(struct iio_dev *indio_dev)
> > > +{
> > > +	struct ad4691_state *st = iio_priv(indio_dev);
> > > +	struct device *dev = regmap_get_device(st->regmap);
> > > +	int ret;
> > > +
> > > +	disable_irq(st->irq);
> > 
> > Should we use disable_irq_sync()?
> 
> Isn't disable_irq() already calling synchronize_irq() inside it? I can't see
> disable_irq_sync() in the current kernel, only disable_irq_nosync().

You're right! Sorry for the noise

- Nuno Sá

> 
> > > +
> > > +	ret = ad4691_sampling_enable(st, false);
> > > +	if (ret)
> > > +		return ret;
> > > +