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[6/9] Input: surface3 - Fix padding for DMA safe buffers.

Message ID 20221127144116.1418083-7-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.

Presumably this part is little used on boards where this could actually
matter so this is mostly about removing code that might be coppied
elsewhere.

Fixes: 4feacbc24eea ("Input: add new driver for the Surface 3")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
---
 drivers/input/touchscreen/surface3_spi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/input/touchscreen/surface3_spi.c b/drivers/input/touchscreen/surface3_spi.c
index 1da23e5585a0..6c884fc2b332 100644
--- a/drivers/input/touchscreen/surface3_spi.c
+++ b/drivers/input/touchscreen/surface3_spi.c
@@ -32,7 +32,7 @@  struct surface3_ts_data {
 	struct input_dev *pen_input_dev;
 	int pen_tool;
 
-	u8 rd_buf[SURFACE3_PACKET_SIZE]		____cacheline_aligned;
+	u8 rd_buf[SURFACE3_PACKET_SIZE] __aligned(ARCH_KMALLOC_MINALIGN;
 };
 
 struct surface3_ts_data_finger {