linux-kernel - [PATCH 5.18 0593/1095] iio: adc: ad7266: Fix alignment for DMA safety

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Message-Id: <20220815180454.082516568@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 19:59:52 +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 0593/1095] iio: adc: ad7266: Fix alignment for DMA safety

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

[ Upstream commit b990cdfe7536a8da7e134d516350402981300016 ]

____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 that DMA safety 'may' require separate
cachelines.

Fixes: 54e018da3141 ("iio:ad7266: Mark transfer buffer as __be16")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Acked-by: Nuno Sá <nuno.sa@...log.com>
Link: https://lore.kernel.org/r/20220508175712.647246-10-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/adc/ad7266.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7266.c b/drivers/iio/adc/ad7266.c
index c17d9b5fbaf6..53c83e04dde5 100644
--- a/drivers/iio/adc/ad7266.c
+++ b/drivers/iio/adc/ad7266.c
@@ -37,7 +37,7 @@ struct ad7266_state {
 	struct gpio_desc	*gpios[3];
 
 	/*
-	 * DMA (thus cache coherency maintenance) requires the
+	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.
 	 * The buffer needs to be large enough to hold two samples (4 bytes) and
 	 * the naturally aligned timestamp (8 bytes).
@@ -45,7 +45,7 @@ struct ad7266_state {
 	struct {
 		__be16 sample[2];
 		s64 timestamp;
-	} data ____cacheline_aligned;
+	} data __aligned(IIO_DMA_MINALIGN);
 };
 
 static int ad7266_wakeup(struct ad7266_state *st)
-- 
2.35.1