Patch "iio: adc: stm32: fix scan of multiple channels with DMA" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

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

    iio: adc: stm32: fix scan of multiple channels with DMA

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iio-adc-stm32-fix-scan-of-multiple-channels-with-dma.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 04e491ca9df60ffe8637d00d68e5ab8bc73b30d5 Mon Sep 17 00:00:00 2001
From: Fabrice Gasnier <fabrice.gasnier@st.com>
Date: Fri, 5 Jan 2018 15:34:54 +0100
Subject: iio: adc: stm32: fix scan of multiple channels with DMA

From: Fabrice Gasnier <fabrice.gasnier@st.com>

commit 04e491ca9df60ffe8637d00d68e5ab8bc73b30d5 upstream.

By default, watermark is set to '1'. Watermark is used to fine tune
cyclic dma buffer period. In case watermark is left untouched (e.g. 1)
and several channels are being scanned, buffer period is wrongly set
(e.g. to 1 sample). As a consequence, data is never pushed to upper layer.
Fix buffer period size, by taking scan channels number into account.

Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iio/adc/stm32-adc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1314,6 +1314,7 @@ static int stm32_adc_set_watermark(struc
 {
 	struct stm32_adc *adc = iio_priv(indio_dev);
 	unsigned int watermark = STM32_DMA_BUFFER_SIZE / 2;
+	unsigned int rx_buf_sz = STM32_DMA_BUFFER_SIZE;
 
 	/*
 	 * dma cyclic transfers are used, buffer is split into two periods.
@@ -1322,7 +1323,7 @@ static int stm32_adc_set_watermark(struc
 	 * - one buffer (period) driver can push with iio_trigger_poll().
 	 */
 	watermark = min(watermark, val * (unsigned)(sizeof(u16)));
-	adc->rx_buf_sz = watermark * 2;
+	adc->rx_buf_sz = min(rx_buf_sz, watermark * 2 * adc->num_conv);
 
 	return 0;
 }


Patches currently in stable-queue which might be from fabrice.gasnier@st.com are

queue-4.14/iio-adc-stm32-fix-scan-of-multiple-channels-with-dma.patch