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

Greg Kroah-Hartman
2022-08-15T21:37:08Z

From: Jonathan Cameron <Jonathan.Cameron@huawei.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@huawei.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-16-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.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