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[5/9] Input: cyttsp - Fix padding for DMA safe buffers.

Message ID 20221127144116.1418083-6-jic23@kernel.org
State New
Headers show
Series Input: Fix insufficent DMA alignment. | expand

Commit Message

Jonathan Cameron Nov. 27, 2022, 2:41 p.m. UTC 
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

On some architectures (e.g. arm64), ____cachline_aligned only aligns
to the cacheline size of the L1 cache size. L1_CACHE_BYTES in
arch64/include/asm/cache.h  Unfortunately DMA safety on these
architectures requires the buffer no share a last level cache cacheline
given by ARCH_DMA_MINALIGN which has a greater granularity.
ARCH_DMA_MINALIGN is not defined for all architectures, but when it is
defined it is used to set the size of ARCH_KMALLOC_MINALIGN
to allow DMA safe buffer allocations.

As such the correct alignment requirement is
__aligned(ARCH_KMALLOC_MINALIGN).
This has recently been fixed in other subsystems such as IIO.

Fixes tag for this is complex as at the time of original introduction, it
is likely that there were no cases where the two alignments were different.

Fixes: 4065d1e7b216 ("Input: add Cypress TTSP capacitive multi-touch screen support")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Javier Martinez Canillas <javier@dowhile0.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/input/touchscreen/cyttsp_core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/input/touchscreen/cyttsp_core.h b/drivers/input/touchscreen/cyttsp_core.h
index 075509e695a2..e87cb323623c 100644
--- a/drivers/input/touchscreen/cyttsp_core.h
+++ b/drivers/input/touchscreen/cyttsp_core.h
@@ -131,7 +131,7 @@  struct cyttsp {
 	u8 lp_intrvl;
 	u8 *bl_keys;
 
-	u8 xfer_buf[] ____cacheline_aligned;
+	u8 xfer_buf[] __aligned(ARCH_KMALLOC_MINALIGN);
 };
 
 struct cyttsp *cyttsp_probe(const struct cyttsp_bus_ops *bus_ops,