Aligning to the L1 cache does not guarantee the same alignment as
kmallocing an object [1]. Furthermore, in some platforms, that
alignment is not sufficient for DMA safety (in case someone wants
to have a DMA safe buffer in privdata) [2].
Sometime ago, we had the same fixes in IIO.
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/devres.c#n35
[2]: https://lore.kernel.org/linux-iio/
20220508175712.647246-2-jic23@kernel.org/
Fixes: c18e2760308e ("counter: Provide alternative counter registration functions")
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240209-counter-align-fix-v2-1-5777ea0a2722@analog.com
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
struct counter_device counter;
/*
- * This is cache line aligned to ensure private data behaves like if it
- * were kmalloced separately.
+ * This ensures private data behaves like if it were kmalloced
+ * separately. Also ensures the minimum alignment for safe DMA
+ * operations (which may or may not mean cache alignment).
*/
- unsigned long privdata[] ____cacheline_aligned;
+ unsigned long privdata[] __aligned(ARCH_DMA_MINALIGN);
};
static void counter_device_release(struct device *dev)