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iio: make IIO_DMA_MINALIGN minimum of 8 bytes

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Add a condition to ensure that IIO_DMA_MINALIGN is at least 8 bytes.
On some 32-bit architectures, IIO_DMA_MINALIGN is 4. In many cases,
drivers are using this alignment for buffers that include a 64-bit
timestamp that is used with iio_push_to_buffers_with_ts(), which expects
the timestamp to be aligned to 8 bytes. To handle this, we can just make
IIO_DMA_MINALIGN at least 8 bytes.

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250507-iio-introduce-iio_declare_buffer_with_ts-v6-1-4aee1b9f1b89@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
David Lechner
2025-05-07 15:42:40 -05:00
committed by Jonathan Cameron
parent 666eae6c6d
commit fa19c30325
1 changed files with 8 additions and 1 deletions
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9
include/linux/iio/iio.h
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@@ -10,6 +10,7 @@
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/compiler_types.h>
#include <linux/minmax.h>
#include <linux/slab.h>
#include <linux/iio/types.h>
/* IIO TODO LIST */
@@ -775,8 +776,14 @@ static inline void *iio_device_get_drvdata(const struct iio_dev *indio_dev)
* to in turn include IIO_DMA_MINALIGN'd elements such as buffers which
* must not share cachelines with the rest of the structure, thus making
* them safe for use with non-coherent DMA.
*
* A number of drivers also use this on buffers that include a 64-bit timestamp
* that is used with iio_push_to_buffer_with_ts(). Therefore, in the case where
* DMA alignment is not sufficient for proper timestamp alignment, we align to
* 8 bytes instead.
*/
#define IIO_DMA_MINALIGN ARCH_DMA_MINALIGN
#define IIO_DMA_MINALIGN MAX(ARCH_DMA_MINALIGN, sizeof(s64))
struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv);
/* The information at the returned address is guaranteed to be cacheline aligned */