patch "iio: adc: ad7380: fix SPI offload trigger rate" added to char-misc-linus

patch "iio: adc: ad7380: fix SPI offload trigger rate" added to char-misc-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio: adc: ad7380: fix SPI offload trigger rate

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From 632757312d7eb320b66ca60e0cfe098ec53cee08 Mon Sep 17 00:00:00 2001
From: David Lechner <dlechner@baylibre.com>
Date: Fri, 19 Sep 2025 15:50:34 -0500
Subject: iio: adc: ad7380: fix SPI offload trigger rate

Add a special case to double the SPI offload trigger rate when all
channels of a single-ended chip are enabled in a buffered read.

The single-ended chips in the AD738x family can only do simultaneous
sampling of half their channels and have a multiplexer to allow reading
the other half. To comply with the IIO definition of sampling_frequency,
we need to trigger twice as often when the sequencer is enabled to so
that both banks can be read in a single sample period.

Fixes: bbeaec81a03e ("iio: ad7380: add support for SPI offload")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/adc/ad7380.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index fa251dc1aae6..bfd908deefc0 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -1227,6 +1227,14 @@ static int ad7380_offload_buffer_postenable(struct iio_dev *indio_dev)
 	if (ret)
 		return ret;
 
+	/*
+	 * When the sequencer is required to read all channels, we need to
+	 * trigger twice per sample period in order to read one complete set
+	 * of samples.
+	 */
+	if (st->seq)
+		config.periodic.frequency_hz *= 2;
+
 	ret = spi_offload_trigger_enable(st->offload, st->offload_trigger, &config);
 	if (ret)
 		spi_unoptimize_message(&st->offload_msg);
-- 
2.51.2