linux-kernel - [PATCH 5.18 0602/1095] iio: adc: ad7923: Fix alignment for DMA safety

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Date:   Mon, 15 Aug 2022 20:00:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 0602/1095] iio: adc: ad7923: Fix alignment for DMA safety

From: Jonathan Cameron <Jonathan.Cameron@...wei.com>

[ Upstream commit 908af45d7057345bc910940a9340f7a1d8935875 ]

____cacheline_aligned is an insufficient guarantee for non-coherent DMA
on platforms with 128 byte cachelines above L1.  Switch to the updated
IIO_DMA_MINALIGN definition.

Update the comment to include 'may'.

Note that some other fixes have applied to this line of code
that may complicate automated backporting.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Fixes: 0eac259db28f ("IIO ADC support for AD7923")
Acked-by: Nuno Sá <nuno.sa@...log.com>
Link: https://lore.kernel.org/r/20220508175712.647246-19-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/adc/ad7923.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7923.c b/drivers/iio/adc/ad7923.c
index 069b561ee768..edad1f30121d 100644
--- a/drivers/iio/adc/ad7923.c
+++ b/drivers/iio/adc/ad7923.c
@@ -57,12 +57,12 @@ struct ad7923_state {
 	unsigned int			settings;
 
 	/*
-	 * DMA (thus cache coherency maintenance) requires the
+	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.
 	 * Ensure rx_buf can be directly used in iio_push_to_buffers_with_timetamp
 	 * Length = 8 channels + 4 extra for 8 byte timestamp
 	 */
-	__be16				rx_buf[12] ____cacheline_aligned;
+	__be16				rx_buf[12] __aligned(IIO_DMA_MINALIGN);
 	__be16				tx_buf[4];
 };
 
-- 
2.35.1