linux-kernel - [PATCH 5.19 0694/1157] iio: frequency: ad9523: Fix alignment for DMA safety

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Date:   Mon, 15 Aug 2022 20:00:50 +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 5.19 0694/1157] iio: frequency: ad9523: Fix alignment for DMA safety

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

[ Upstream commit 8ff2eb625c353b1491d9f89f1dfd52e7aef5734c ]

____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.

Updated help text to 'may' require buffers to be in their own cacheline.

Fixes: cd1678f96329 ("iio: frequency: New driver for AD9523 SPI Low Jitter Clock Generator")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Acked-by: Nuno Sá <nuno.sa@...log.com>
Link: https://lore.kernel.org/r/20220508175712.647246-66-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/frequency/ad9523.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/frequency/ad9523.c b/drivers/iio/frequency/ad9523.c
index 942870539268..97662ca1ca96 100644
--- a/drivers/iio/frequency/ad9523.c
+++ b/drivers/iio/frequency/ad9523.c
@@ -287,13 +287,13 @@ struct ad9523_state {
 	struct mutex		lock;
 
 	/*
-	 * DMA (thus cache coherency maintenance) requires the
-	 * transfer buffers to live in their own cache lines.
+	 * DMA (thus cache coherency maintenance) may require that
+	 * transfer buffers live in their own cache lines.
 	 */
 	union {
 		__be32 d32;
 		u8 d8[4];
-	} data[2] ____cacheline_aligned;
+	} data[2] __aligned(IIO_DMA_MINALIGN);
 };
 
 static int ad9523_read(struct iio_dev *indio_dev, unsigned int addr)
-- 
2.35.1