[PATCH v13 5/6] iio: adc: ad4691: add oversampling support
From: Radu Sabau via B4 Relay
Date: Mon May 25 2026 - 06:12:37 EST
From: Radu Sabau <radu.sabau@xxxxxxxxxx>
Add per-channel oversampling ratio (OSR) support for CNV burst mode.
The accumulator depth register (ACC_DEPTH_IN) is programmed with the
selected OSR at buffer enable time and before each single-shot read.
Supported OSR values: 1, 2, 4, 8, 16, 32.
Introduce AD4691_MANUAL_CHANNEL() for manual mode channels, which do
not expose the oversampling_ratio attribute since OSR is not applicable
in that mode. A separate manual_channels array is added to
struct ad4691_channel_info and selected at probe time.
in_voltageN_sampling_frequency represents the effective output rate for
channel N, defined as osc_freq / osr[N]. The chip has one internal
oscillator shared by all channels; each channel independently
accumulates osr[N] oscillator cycles before producing a result.
Writing sampling_frequency computes needed_osc = freq * osr[N] and
snaps down to the largest oscillator table entry that satisfies both
osc <= needed_osc and osc % osr[N] == 0, guaranteeing an exact integer
read-back. The result is stored in target_osc_freq_Hz and written to
OSC_FREQ_REG at buffer enable and single-shot time, so sampling_frequency
and oversampling_ratio can be set in any order.
in_voltageN_sampling_frequency_available is precomputed at probe for
each OSR value, listing only oscillator table entries that divide
evenly by that OSR, expressed as effective rates (osc_freq / osr[N]).
The list becomes sparser as OSR increases, capping at max_rate / osr[N].
read_avail picks the precomputed list for the channel's current OSR,
making the returned pointer stable and race-free.
Writing oversampling_ratio stores the new OSR for that channel and snaps
target_osc_freq_Hz to the largest oscillator table entry that is both
<= old_effective_rate * new_osr and evenly divisible by new_osr. This
preserves an integer read-back of in_voltageN_sampling_frequency after
the OSR change while keeping the oscillator as close as possible to the
previous effective rate.
OSR defaults to 1 (no accumulation) for all channels.
Signed-off-by: Radu Sabau <radu.sabau@xxxxxxxxxx>
---
drivers/iio/adc/ad4691.c | 357 +++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 327 insertions(+), 30 deletions(-)
diff --git a/drivers/iio/adc/ad4691.c b/drivers/iio/adc/ad4691.c
index 6563488ab8b8..64238f842841 100644
--- a/drivers/iio/adc/ad4691.c
+++ b/drivers/iio/adc/ad4691.c
@@ -121,6 +121,7 @@ enum ad4691_ref_ctrl {
struct ad4691_channel_info {
const struct iio_chan_spec *channels __counted_by_ptr(num_channels);
+ const struct iio_chan_spec *manual_channels __counted_by_ptr(num_channels);
unsigned int num_channels;
};
@@ -131,7 +132,34 @@ struct ad4691_chip_info {
const struct ad4691_channel_info *offload_info;
};
+/* CNV burst mode channel — exposes oversampling ratio. */
#define AD4691_CHANNEL(ch) \
+ { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) \
+ | BIT(IIO_CHAN_INFO_SAMP_FREQ) \
+ | BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+ .info_mask_shared_by_all_available = \
+ BIT(IIO_CHAN_INFO_SAMP_FREQ) \
+ | BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+ .channel = ch, \
+ .scan_index = ch, \
+ .scan_type = { \
+ .format = 'u', \
+ .realbits = 16, \
+ .storagebits = 16, \
+ .endianness = IIO_BE, \
+ }, \
+ }
+
+/*
+ * Manual mode channel — no oversampling ratio attribute. OSR is not
+ * supported in manual mode; ACC_DEPTH_IN is not configured during manual
+ * buffer enable.
+ */
+#define AD4691_MANUAL_CHANNEL(ch) \
{ \
.type = IIO_VOLTAGE, \
.indexed = 1, \
@@ -155,8 +183,33 @@ struct ad4691_chip_info {
* bits into native 16-bit words before DMA, so samples are in
* CPU-native byte order (IIO_CPU). storagebits=16 matches the 16-bit
* DMA word size.
+ *
+ * CNV burst offload configures ACC_DEPTH_IN per channel, so the
+ * oversampling_ratio attribute is exposed. Manual offload does not;
+ * use AD4691_OFFLOAD_MANUAL_CHANNEL for that path.
*/
#define AD4691_OFFLOAD_CHANNEL(ch) \
+ { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) \
+ | BIT(IIO_CHAN_INFO_SAMP_FREQ) \
+ | BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+ .info_mask_shared_by_all_available = \
+ BIT(IIO_CHAN_INFO_SAMP_FREQ) \
+ | BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+ .channel = ch, \
+ .scan_index = ch, \
+ .scan_type = { \
+ .format = 'u', \
+ .realbits = 16, \
+ .storagebits = 16, \
+ }, \
+ }
+
+/* Manual offload — same IIO_CPU layout but no oversampling_ratio attribute. */
+#define AD4691_OFFLOAD_MANUAL_CHANNEL(ch) \
{ \
.type = IIO_VOLTAGE, \
.indexed = 1, \
@@ -240,23 +293,91 @@ static const struct iio_chan_spec ad4693_offload_channels[] = {
AD4691_OFFLOAD_CHANNEL(7),
};
+static const struct iio_chan_spec ad4691_manual_channels[] = {
+ AD4691_MANUAL_CHANNEL(0),
+ AD4691_MANUAL_CHANNEL(1),
+ AD4691_MANUAL_CHANNEL(2),
+ AD4691_MANUAL_CHANNEL(3),
+ AD4691_MANUAL_CHANNEL(4),
+ AD4691_MANUAL_CHANNEL(5),
+ AD4691_MANUAL_CHANNEL(6),
+ AD4691_MANUAL_CHANNEL(7),
+ AD4691_MANUAL_CHANNEL(8),
+ AD4691_MANUAL_CHANNEL(9),
+ AD4691_MANUAL_CHANNEL(10),
+ AD4691_MANUAL_CHANNEL(11),
+ AD4691_MANUAL_CHANNEL(12),
+ AD4691_MANUAL_CHANNEL(13),
+ AD4691_MANUAL_CHANNEL(14),
+ AD4691_MANUAL_CHANNEL(15),
+ IIO_CHAN_SOFT_TIMESTAMP(16),
+};
+
+static const struct iio_chan_spec ad4693_manual_channels[] = {
+ AD4691_MANUAL_CHANNEL(0),
+ AD4691_MANUAL_CHANNEL(1),
+ AD4691_MANUAL_CHANNEL(2),
+ AD4691_MANUAL_CHANNEL(3),
+ AD4691_MANUAL_CHANNEL(4),
+ AD4691_MANUAL_CHANNEL(5),
+ AD4691_MANUAL_CHANNEL(6),
+ AD4691_MANUAL_CHANNEL(7),
+ IIO_CHAN_SOFT_TIMESTAMP(8),
+};
+
+static const struct iio_chan_spec ad4691_offload_manual_channels[] = {
+ AD4691_OFFLOAD_MANUAL_CHANNEL(0),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(1),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(2),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(3),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(4),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(5),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(6),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(7),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(8),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(9),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(10),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(11),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(12),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(13),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(14),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(15),
+};
+
+static const struct iio_chan_spec ad4693_offload_manual_channels[] = {
+ AD4691_OFFLOAD_MANUAL_CHANNEL(0),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(1),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(2),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(3),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(4),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(5),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(6),
+ AD4691_OFFLOAD_MANUAL_CHANNEL(7),
+};
+
+static const int ad4691_oversampling_ratios[] = { 1, 2, 4, 8, 16, 32 };
+
static const struct ad4691_channel_info ad4691_sw_info = {
.channels = ad4691_channels,
+ .manual_channels = ad4691_manual_channels,
.num_channels = ARRAY_SIZE(ad4691_channels),
};
static const struct ad4691_channel_info ad4693_sw_info = {
.channels = ad4693_channels,
+ .manual_channels = ad4693_manual_channels,
.num_channels = ARRAY_SIZE(ad4693_channels),
};
static const struct ad4691_channel_info ad4691_offload_info = {
.channels = ad4691_offload_channels,
+ .manual_channels = ad4691_offload_manual_channels,
.num_channels = ARRAY_SIZE(ad4691_offload_channels),
};
static const struct ad4691_channel_info ad4693_offload_info = {
.channels = ad4693_offload_channels,
+ .manual_channels = ad4693_offload_manual_channels,
.num_channels = ARRAY_SIZE(ad4693_offload_channels),
};
@@ -323,6 +444,25 @@ struct ad4691_state {
int irq;
int vref_uV;
u32 cnv_period_ns;
+ /*
+ * Snapped oscillator frequency (Hz) shared by all channels. Set when
+ * sampling_frequency or oversampling_ratio is written; written to
+ * OSC_FREQ_REG at buffer enable and single-shot time so both attributes
+ * can be set in any order. Reading in_voltage_sampling_frequency
+ * returns target_osc_freq_Hz / osr — the effective rate given the
+ * shared oversampling ratio.
+ */
+ u32 target_osc_freq_Hz;
+ /* Shared oversampling ratio across all channels; always 1 in manual mode. */
+ unsigned int osr;
+ /*
+ * Precomputed effective-rate lists, one row per entry in
+ * ad4691_oversampling_ratios[]. Populated at probe; read_avail picks
+ * the row for the current shared OSR. The tables are stable after
+ * probe so returning a pointer into them from read_avail is race-free.
+ */
+ int samp_freq_avail[ARRAY_SIZE(ad4691_oversampling_ratios)][ARRAY_SIZE(ad4691_osc_freqs_Hz)];
+ int samp_freq_avail_len[ARRAY_SIZE(ad4691_oversampling_ratios)];
bool manual_mode;
bool irq_enabled;
@@ -588,35 +728,95 @@ static unsigned int ad4691_samp_freq_start(const struct ad4691_chip_info *info)
return (info->max_rate == 1 * HZ_PER_MHZ) ? 0 : 1;
}
-static int ad4691_get_sampling_freq(struct ad4691_state *st, int *val)
+/*
+ * Find the largest oscillator table entry that is both <= needed_osc and
+ * evenly divisible by osr (guaranteeing an integer effective rate on
+ * read-back). Returns 0 if no such entry exists in the chip's valid range.
+ */
+static unsigned int ad4691_find_osc_freq(struct ad4691_state *st,
+ unsigned int needed_osc,
+ unsigned int osr)
{
- unsigned int reg_val;
- int ret;
+ unsigned int start = ad4691_samp_freq_start(st->info);
- guard(mutex)(&st->lock);
+ for (unsigned int i = start; i < ARRAY_SIZE(ad4691_osc_freqs_Hz); i++) {
+ if ((unsigned int)ad4691_osc_freqs_Hz[i] > needed_osc)
+ continue;
+ if (ad4691_osc_freqs_Hz[i] % osr)
+ continue;
+ return ad4691_osc_freqs_Hz[i];
+ }
+ return 0;
+}
- ret = regmap_read(st->regmap, AD4691_OSC_FREQ_REG, ®_val);
- if (ret)
- return ret;
+/* Write target_osc_freq_Hz to OSC_FREQ_REG. Called at use time. */
+static int ad4691_write_osc_freq(struct ad4691_state *st)
+{
+ for (unsigned int i = 0; i < ARRAY_SIZE(ad4691_osc_freqs_Hz); i++) {
+ if (ad4691_osc_freqs_Hz[i] == st->target_osc_freq_Hz)
+ return regmap_write(st->regmap, AD4691_OSC_FREQ_REG, i);
+ }
+ return -EINVAL;
+}
- *val = ad4691_osc_freqs_Hz[FIELD_GET(AD4691_OSC_FREQ_MASK, reg_val)];
- return IIO_VAL_INT;
+/* Return the index of osr in ad4691_oversampling_ratios[], defaulting to 0. */
+static unsigned int ad4691_osr_index(unsigned int osr)
+{
+ for (unsigned int i = 0; i < ARRAY_SIZE(ad4691_oversampling_ratios) - 1; i++) {
+ if ((unsigned int)ad4691_oversampling_ratios[i] == osr)
+ return i;
+ }
+ return ARRAY_SIZE(ad4691_oversampling_ratios) - 1;
+}
+
+/*
+ * Precompute samp_freq_avail[][]: for each OSR value, list the oscillator
+ * table entries that divide evenly by that OSR, expressed as effective rates
+ * (osc_freq / osr). Called once at probe after st->info is set.
+ */
+static void ad4691_precompute_samp_freq_avail(struct ad4691_state *st)
+{
+ unsigned int start = ad4691_samp_freq_start(st->info);
+
+ for (unsigned int i = 0; i < ARRAY_SIZE(ad4691_oversampling_ratios); i++) {
+ unsigned int osr = ad4691_oversampling_ratios[i];
+ int n = 0;
+
+ for (unsigned int j = start; j < ARRAY_SIZE(ad4691_osc_freqs_Hz); j++) {
+ if (ad4691_osc_freqs_Hz[j] % osr)
+ continue;
+ st->samp_freq_avail[i][n++] = ad4691_osc_freqs_Hz[j] / osr;
+ }
+ st->samp_freq_avail_len[i] = n;
+ }
}
static int ad4691_set_sampling_freq(struct ad4691_state *st, int freq)
{
- unsigned int start = ad4691_samp_freq_start(st->info);
+ unsigned int osr, found;
+ /*
+ * Read osr under st->lock: osr and target_osc_freq_Hz are modified
+ * together under the lock; reading after acquiring it ensures we see
+ * a consistent snapshot with no concurrent write racing us.
+ */
guard(mutex)(&st->lock);
+ osr = st->osr;
- for (unsigned int i = start; i < ARRAY_SIZE(ad4691_osc_freqs_Hz); i++) {
- if (ad4691_osc_freqs_Hz[i] != freq)
- continue;
- return regmap_update_bits(st->regmap, AD4691_OSC_FREQ_REG,
- AD4691_OSC_FREQ_MASK, i);
- }
+ if (freq <= 0 || (unsigned int)freq > st->info->max_rate / osr)
+ return -EINVAL;
- return -EINVAL;
+ found = ad4691_find_osc_freq(st, (unsigned int)freq * osr, osr);
+ if (!found)
+ return -EINVAL;
+
+ /*
+ * Store the snapped oscillator frequency; OSC_FREQ_REG is written at
+ * buffer enable and single-shot time so that sampling_frequency and
+ * oversampling_ratio can be set in any order.
+ */
+ st->target_osc_freq_Hz = found;
+ return 0;
}
static int ad4691_read_avail(struct iio_dev *indio_dev,
@@ -625,13 +825,27 @@ static int ad4691_read_avail(struct iio_dev *indio_dev,
int *length, long mask)
{
struct ad4691_state *st = iio_priv(indio_dev);
- unsigned int start = ad4691_samp_freq_start(st->info);
switch (mask) {
- case IIO_CHAN_INFO_SAMP_FREQ:
- *vals = &ad4691_osc_freqs_Hz[start];
+ case IIO_CHAN_INFO_SAMP_FREQ: {
+ unsigned int osr_idx;
+
+ /*
+ * The precomputed tables are stable after probe; only the
+ * current OSR needs to be read under the lock to pick the
+ * right row atomically.
+ */
+ guard(mutex)(&st->lock);
+ osr_idx = ad4691_osr_index(st->osr);
+ *vals = st->samp_freq_avail[osr_idx];
*type = IIO_VAL_INT;
- *length = ARRAY_SIZE(ad4691_osc_freqs_Hz) - start;
+ *length = st->samp_freq_avail_len[osr_idx];
+ return IIO_AVAIL_LIST;
+ }
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ *vals = ad4691_oversampling_ratios;
+ *type = IIO_VAL_INT;
+ *length = ARRAY_SIZE(ad4691_oversampling_ratios);
return IIO_AVAIL_LIST;
default:
return -EINVAL;
@@ -642,7 +856,7 @@ 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, osc_idx, period_us;
+ unsigned int reg_val, period_us;
int ret;
guard(mutex)(&st->lock);
@@ -662,7 +876,11 @@ static int ad4691_single_shot_read(struct iio_dev *indio_dev,
if (ret)
return ret;
- ret = regmap_read(st->regmap, AD4691_OSC_FREQ_REG, ®_val);
+ ret = regmap_write(st->regmap, AD4691_ACC_DEPTH_IN(0), st->osr);
+ if (ret)
+ return ret;
+
+ ret = ad4691_write_osc_freq(st);
if (ret)
return ret;
@@ -670,9 +888,12 @@ static int ad4691_single_shot_read(struct iio_dev *indio_dev,
if (ret)
return ret;
- osc_idx = FIELD_GET(AD4691_OSC_FREQ_MASK, reg_val);
- /* Wait 2 oscillator periods for the conversion to complete. */
- period_us = DIV_ROUND_UP(2UL * USEC_PER_SEC, ad4691_osc_freqs_Hz[osc_idx]);
+ /*
+ * Wait osr + 1 oscillator periods: osr for accumulation, +1 for the
+ * pipeline margin (one extra period ensures the final result is ready).
+ */
+ period_us = DIV_ROUND_UP((st->osr + 1) * USEC_PER_SEC,
+ st->target_osc_freq_Hz);
fsleep(period_us);
ret = regmap_write(st->regmap, AD4691_OSC_EN_REG, 0);
@@ -706,8 +927,22 @@ static int ad4691_read_raw(struct iio_dev *indio_dev,
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_SAMP_FREQ: {
+ /*
+ * Read target_osc_freq_Hz and osr under st->lock to get a
+ * consistent snapshot: write_raw for SAMP_FREQ or OSR modifies
+ * both fields under the lock, so a concurrent read without the
+ * lock could observe a new oscillator frequency with the old OSR.
+ */
+ guard(mutex)(&st->lock);
+ *val = st->target_osc_freq_Hz / st->osr;
+ return IIO_VAL_INT;
+ }
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO: {
+ guard(mutex)(&st->lock);
+ *val = st->osr;
+ return IIO_VAL_INT;
+ }
case IIO_CHAN_INFO_SCALE:
*val = st->vref_uV / (MICRO / MILLI);
*val2 = chan->scan_type.realbits;
@@ -730,6 +965,33 @@ static int ad4691_write_raw(struct iio_dev *indio_dev,
switch (mask) {
case IIO_CHAN_INFO_SAMP_FREQ:
return ad4691_set_sampling_freq(st, val);
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO: {
+ unsigned int old_effective, found, osr_idx;
+
+ osr_idx = ad4691_osr_index(val);
+ if (ad4691_oversampling_ratios[osr_idx] != val)
+ return -EINVAL;
+
+ /*
+ * Hold st->lock while computing the new oscillator frequency
+ * and updating both target_osc_freq_Hz and osr atomically:
+ * read_raw for SAMP_FREQ reads both fields under the lock and
+ * must see a consistent pair (new osc ↔ new osr).
+ *
+ * Snap target_osc_freq_Hz to the largest table entry that is
+ * both <= old_effective * new_osr and evenly divisible by
+ * new_osr, preserving an integer read-back of
+ * in_voltage_sampling_frequency after the OSR change.
+ */
+ guard(mutex)(&st->lock);
+ old_effective = st->target_osc_freq_Hz / st->osr;
+ found = ad4691_find_osc_freq(st, old_effective * (unsigned int)val, val);
+ if (!found)
+ return -EINVAL;
+ st->target_osc_freq_Hz = found;
+ st->osr = val;
+ return 0;
+ }
default:
return -EINVAL;
}
@@ -784,6 +1046,10 @@ static int ad4691_enter_conversion_mode(struct ad4691_state *st)
return regmap_update_bits(st->regmap, AD4691_DEVICE_SETUP,
AD4691_MANUAL_MODE, AD4691_MANUAL_MODE);
+ ret = ad4691_write_osc_freq(st);
+ if (ret)
+ return ret;
+
ret = regmap_update_bits(st->regmap, AD4691_ADC_SETUP,
AD4691_ADC_MODE_MASK, AD4691_CNV_BURST_MODE);
if (ret)
@@ -943,6 +1209,10 @@ static int ad4691_cnv_burst_buffer_preenable(struct iio_dev *indio_dev)
if (ret)
goto err_unoptimize;
+ ret = regmap_write(st->regmap, AD4691_ACC_DEPTH_IN(0), st->osr);
+ if (ret)
+ goto err_unoptimize;
+
ret = ad4691_enter_conversion_mode(st);
if (ret)
goto err_unoptimize;
@@ -1122,6 +1392,10 @@ static int ad4691_cnv_burst_offload_buffer_postenable(struct iio_dev *indio_dev)
if (ret)
return ret;
+ ret = regmap_write(st->regmap, AD4691_ACC_DEPTH_IN(0), st->osr);
+ if (ret)
+ return ret;
+
ret = ad4691_enter_conversion_mode(st);
if (ret)
return ret;
@@ -1538,11 +1812,15 @@ static int ad4691_config(struct ad4691_state *st)
if (ret)
return dev_err_probe(dev, ret, "Failed to write OSC_FREQ\n");
+ st->target_osc_freq_Hz = ad4691_osc_freqs_Hz[ad4691_samp_freq_start(st->info)];
+
ret = regmap_update_bits(st->regmap, AD4691_ADC_SETUP,
AD4691_ADC_MODE_MASK, AD4691_AUTONOMOUS_MODE);
if (ret)
return dev_err_probe(dev, ret, "Failed to write ADC_SETUP\n");
+ ad4691_precompute_samp_freq_avail(st);
+
return 0;
}
@@ -1554,7 +1832,14 @@ static int ad4691_setup_triggered_buffer(struct iio_dev *indio_dev,
unsigned int i;
int irq, ret;
- indio_dev->channels = st->info->sw_info->channels;
+ /*
+ * Manual mode exposes channels without the oversampling_ratio attribute
+ * because ACC_DEPTH_IN is not configured in manual mode.
+ */
+ if (st->manual_mode)
+ indio_dev->channels = st->info->sw_info->manual_channels;
+ else
+ indio_dev->channels = st->info->sw_info->channels;
indio_dev->num_channels = st->info->sw_info->num_channels;
indio_dev->info = st->manual_mode ? &ad4691_manual_info : &ad4691_cnv_burst_info;
@@ -1636,7 +1921,18 @@ static int ad4691_setup_offload(struct iio_dev *indio_dev,
st->offload = spi_offload;
- indio_dev->channels = st->info->offload_info->channels;
+ /*
+ * CNV burst offload exposes oversampling_ratio (ACC_DEPTH_IN is
+ * configured per channel at buffer enable). Manual offload does not
+ * configure ACC_DEPTH_IN, so it uses a separate channel array
+ * without the oversampling_ratio attribute. Both paths use IIO_CPU
+ * (no .endianness annotation) because bits_per_word=16 causes the
+ * SPI Engine to produce native 16-bit DMA words.
+ */
+ if (st->manual_mode)
+ indio_dev->channels = st->info->offload_info->manual_channels;
+ else
+ indio_dev->channels = st->info->offload_info->channels;
indio_dev->num_channels = st->info->offload_info->num_channels;
/*
* Offload path uses DMA directly; no IIO trigger is involved, so
@@ -1710,6 +2006,7 @@ static int ad4691_probe(struct spi_device *spi)
st->info = spi_get_device_match_data(spi);
if (!st->info)
return -ENODEV;
+ st->osr = 1;
ret = devm_mutex_init(dev, &st->lock);
if (ret)
--
2.43.0