From: Radu Sabau <radu.sabau@analog.com>

ad4695_enter_advanced_sequencer_mode() was called after
spi_offload_trigger_enable(). That is wrong because
ad4695_enter_advanced_sequencer_mode() issues regular SPI transfers to
put the ADC into advanced sequencer mode, and spi_offload_trigger_enable()
enables the PWM trigger that drives CNV. Once the PWM is running, CNV
pulses start arriving and the offload engine owns the SPI bus; any
concurrent regular SPI transfer produces undefined behaviour.

Fix this by calling ad4695_enter_advanced_sequencer_mode() before
spi_offload_trigger_enable(), so the ADC is fully configured before the
first CNV pulse can occur. This is consistent with the same constraint
that already applies to the BUSY_GP_EN write above it.

Update the error unwind labels accordingly: add err_exit_conversion_mode
so that a failure of spi_offload_trigger_enable() correctly exits
conversion mode before clearing BUSY_GP_EN.

Fixes: f09f140e3ea8 ("iio: adc: ad4695: Add support for SPI offload")
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Radu Sabau <radu.sabau@analog.com>
---
ad4695_enter_advanced_sequencer_mode() issues regular SPI transfers to
configure the ADC. These must complete before spi_offload_trigger_enable()
enables the PWM/CNV trigger, because once CNV pulses are live the offload
engine owns the SPI bus.

This fixes the call ordering and updates the error unwind path accordingly.
---
Changes in v2:
- Reword commit message to explain the correct bus-ownership
  invariant directly, without reference to the HDL bug that
  exposed it.
- Remove unnecessary comment since the error path changed.
- Link to v1: https://lore.kernel.org/r/20260330-ad4696-fix-v1-1-e841e96451b2@analog.com
---
 drivers/iio/adc/ad4695.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
index cda419638d9a..4471acd6fd5f 100644
--- a/drivers/iio/adc/ad4695.c
+++ b/drivers/iio/adc/ad4695.c
@@ -876,14 +876,14 @@ static int ad4695_offload_buffer_postenable(struct iio_dev *indio_dev)
 	if (ret)
 		goto err_unoptimize_message;
 
-	ret = spi_offload_trigger_enable(st->offload, st->offload_trigger,
-					 &config);
+	ret = ad4695_enter_advanced_sequencer_mode(st, num_slots);
 	if (ret)
 		goto err_disable_busy_output;
 
-	ret = ad4695_enter_advanced_sequencer_mode(st, num_slots);
+	ret = spi_offload_trigger_enable(st->offload, st->offload_trigger,
+					 &config);
 	if (ret)
-		goto err_offload_trigger_disable;
+		goto err_exit_conversion_mode;
 
 	mutex_lock(&st->cnv_pwm_lock);
 	pwm_get_state(st->cnv_pwm, &state);
@@ -895,22 +895,15 @@ static int ad4695_offload_buffer_postenable(struct iio_dev *indio_dev)
 	ret = pwm_apply_might_sleep(st->cnv_pwm, &state);
 	mutex_unlock(&st->cnv_pwm_lock);
 	if (ret)
-		goto err_offload_exit_conversion_mode;
+		goto err_trigger_disable;
 
 	return 0;
 
-err_offload_exit_conversion_mode:
-	/*
-	 * We have to unwind in a different order to avoid triggering offload.
-	 * ad4695_exit_conversion_mode() triggers a conversion, so it has to be
-	 * done after spi_offload_trigger_disable().
-	 */
+err_trigger_disable:
 	spi_offload_trigger_disable(st->offload, st->offload_trigger);
-	ad4695_exit_conversion_mode(st);
-	goto err_disable_busy_output;
 
-err_offload_trigger_disable:
-	spi_offload_trigger_disable(st->offload, st->offload_trigger);
+err_exit_conversion_mode:
+	ad4695_exit_conversion_mode(st);
 
 err_disable_busy_output:
 	regmap_clear_bits(st->regmap, AD4695_REG_GP_MODE,

---
base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
change-id: 20260330-ad4696-fix-186955a8c511

Best regards,
-- 
Radu Sabau <radu.sabau@analog.com>