patch "iio: adc: stm32: fix scan of multiple channels with DMA" added to staging-next

patch "iio: adc: stm32: fix scan of multiple channels with DMA" added to staging-next

[gregkh]

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 my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next 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 also be merged in the next major kernel release
during the merge window.

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


>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

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>
Cc: <Stable@vger.kernel.org>
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(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 6dbf9549cdc9..7f5def465340 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1289,6 +1289,7 @@ static int stm32_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
 {
 	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.
@@ -1297,7 +1298,7 @@ static int stm32_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
 	 * - 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;
 }
-- 
2.15.1