iio: frequency: ad9523: Fix alignment for DMA safety

____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@huawei.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-66-jic23@kernel.org

diff --git a/drivers/iio/frequency/ad9523.c b/drivers/iio/frequency/ad9523.c
index 9428705..97662ca 100644 (file)
--- 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)