linux-kernel - [PATCH v4 1/1] spi: offload: Add offset parameter

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Message-ID: <cd315e95c0bd8523f00e91c400abcd6a418e5924.1759760519.git.marcelo.schmitt@analog.com>
Date: Mon, 6 Oct 2025 11:25:41 -0300
From: Marcelo Schmitt <marcelo.schmitt@...log.com>
To: <linux-spi@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: Axel Haslam <ahaslam@...libre.com>, <broonie@...nel.org>,
        <jic23@...nel.org>, <nuno.sa@...log.com>, <dlechner@...libre.com>,
        <andy@...nel.org>, <marcelo.schmitt1@...il.com>
Subject: [PATCH v4 1/1] spi: offload: Add offset parameter

From: Axel Haslam <ahaslam@...libre.com>

Add an offset parameter that can be passed in the periodic trigger.
This is useful for example when ADC drivers implement a separate periodic
signal to trigger conversion and need offload to read the result with
some delay. While at it, add some documentation to offload periodic trigger
parameters.

Reviewed-by: David Lechner <dlechner@...libre.com>
Signed-off-by: Axel Haslam <ahaslam@...libre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
---
Hello,

This patch adds a small feature that is required for a series improving ad4030
in the IIO subsystem [1]. Can we have an immutable branch with this patch so
that it can be used as base for the IIO driver changes?

[1]: https://lore.kernel.org/linux-iio/cover.1758916484.git.marcelo.schmitt@analog.com/

Thanks,
Marcelo

Change log v3 -> v4
- Picked up David's review tag

Change log v2 -> v3
- Squashed SPI offload trigger commits.
- Added documentation to offload trigger periodic parameters.

Change log v1 -> v2
- Use upper case: adc -> ADC.
- Codestyle/readability improvements according to suggestions.

Link to v3: https://lore.kernel.org/linux-spi/d73804d605d494c6420adb7c0b67f6707628832d.1758913065.git.marcelo.schmitt@analog.com/
Link to v2: https://lore.kernel.org/linux-spi/cover.1758206554.git.marcelo.schmitt@analog.com/
Link to v1: https://lore.kernel.org/linux-iio/cover.1756511030.git.marcelo.schmitt@analog.com/

 drivers/spi/spi-offload-trigger-pwm.c | 3 +++
 include/linux/spi/offload/types.h     | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/spi/spi-offload-trigger-pwm.c b/drivers/spi/spi-offload-trigger-pwm.c
index 805ed41560df..3e8c19227edb 100644
--- a/drivers/spi/spi-offload-trigger-pwm.c
+++ b/drivers/spi/spi-offload-trigger-pwm.c
@@ -51,12 +51,14 @@ static int spi_offload_trigger_pwm_validate(struct spi_offload_trigger *trigger,
 	wf.period_length_ns = DIV_ROUND_UP_ULL(NSEC_PER_SEC, periodic->frequency_hz);
 	/* REVISIT: 50% duty-cycle for now - may add config parameter later */
 	wf.duty_length_ns = wf.period_length_ns / 2;
+	wf.duty_offset_ns = periodic->offset_ns;
 
 	ret = pwm_round_waveform_might_sleep(st->pwm, &wf);
 	if (ret < 0)
 		return ret;
 
 	periodic->frequency_hz = DIV_ROUND_UP_ULL(NSEC_PER_SEC, wf.period_length_ns);
+	periodic->offset_ns = wf.duty_offset_ns;
 
 	return 0;
 }
@@ -77,6 +79,7 @@ static int spi_offload_trigger_pwm_enable(struct spi_offload_trigger *trigger,
 	wf.period_length_ns = DIV_ROUND_UP_ULL(NSEC_PER_SEC, periodic->frequency_hz);
 	/* REVISIT: 50% duty-cycle for now - may add config parameter later */
 	wf.duty_length_ns = wf.period_length_ns / 2;
+	wf.duty_offset_ns = periodic->offset_ns;
 
 	return pwm_set_waveform_might_sleep(st->pwm, &wf, false);
 }
diff --git a/include/linux/spi/offload/types.h b/include/linux/spi/offload/types.h
index 6f7892347871..cd61f8adb7a5 100644
--- a/include/linux/spi/offload/types.h
+++ b/include/linux/spi/offload/types.h
@@ -57,8 +57,17 @@ enum spi_offload_trigger_type {
 	SPI_OFFLOAD_TRIGGER_PERIODIC,
 };
 
+/**
+ * spi_offload_trigger_periodic - configuration parameters for periodic triggers
+ * @frequency_hz: The rate that the trigger should fire in Hz.
+ * @offset_ns: A delay in nanoseconds between when this trigger fires
+ *	       compared to another trigger. This requires specialized hardware
+ *	       that supports such synchronization with a delay between two or
+ *	       more triggers. Set to 0 when not needed.
+ */
 struct spi_offload_trigger_periodic {
 	u64 frequency_hz;
+	u64 offset_ns;
 };
 
 struct spi_offload_trigger_config {

base-commit: 23bd49d3a1c042a3fb262299d86110af4cbd073d
-- 
2.39.2