This is a note to let you know that I've just added the patch titled
counter: fix privdata alignment
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
counter-fix-privdata-alignment.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 40db7c1162d3c9e98afbc6f9ff597392acbfed47
Author: Nuno Sa <nuno.sa@xxxxxxxxxx>
Date: Fri Feb 9 16:50:34 2024 +0100
counter: fix privdata alignment
[ Upstream commit c83ccdc9586b3e9882da9e27507c046751999d59 ]
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@xxxxxxxxxx/
Fixes: c18e2760308e ("counter: Provide alternative counter registration functions")
Signed-off-by: Nuno Sa <nuno.sa@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240209-counter-align-fix-v2-1-5777ea0a2722@xxxxxxxxxx
Signed-off-by: William Breathitt Gray <william.gray@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
index 09c77afb33ca8..3f24481fc04a1 100644
--- a/drivers/counter/counter-core.c
+++ b/drivers/counter/counter-core.c
@@ -31,10 +31,11 @@ struct counter_device_allochelper {
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)
