linux-kernel - [PATCH 5.18 0599/1095] iio: adc: ad7766: Fix alignment for DMA safety

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Date:   Mon, 15 Aug 2022 19:59:58 +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>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Nuno Sá <nuno.sa@...log.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 0599/1095] iio: adc: ad7766: Fix alignment for DMA safety

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

[ Upstream commit 009ae227a1dace2d4d27c804e5bd65907e1d0557 ]

____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 reflect the fact DMA safety 'may' require
separate cachelines.

Fixes: aa16c6bd0e09 ("iio:adc: Add support for AD7766/AD7767")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>
Acked-by: Nuno Sá <nuno.sa@...log.com>
Link: https://lore.kernel.org/r/20220508175712.647246-16-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/adc/ad7766.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ad7766.c b/drivers/iio/adc/ad7766.c
index 51ee9482e0df..3079a0872947 100644
--- a/drivers/iio/adc/ad7766.c
+++ b/drivers/iio/adc/ad7766.c
@@ -45,13 +45,12 @@ struct ad7766 {
 	struct spi_message msg;
 
 	/*
-	 * DMA (thus cache coherency maintenance) requires the
+	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.
 	 * Make the buffer large enough for one 24 bit sample and one 64 bit
 	 * aligned 64 bit timestamp.
 	 */
-	unsigned char data[ALIGN(3, sizeof(s64)) + sizeof(s64)]
-			____cacheline_aligned;
+	unsigned char data[ALIGN(3, sizeof(s64)) + sizeof(s64)]	__aligned(IIO_DMA_MINALIGN);
 };
 
 /*
-- 
2.35.1