From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> This problem was discovered in IIO as a side effect of the discussions about relaxing kmalloc alignment on arm64 and resulted in a series of large patch sets. https://lore.kernel.org/linux-iio/20220508175712.647246-1-jic23@xxxxxxxxxx/ Unsurprisingly there are cases of it in other subsystems. The short version of this is that there are a few known arm64 chips where ___cacheline_aligned enforces 64 byte alignment which is what we typically want for performance optimization as the size of the L1 cache lines. However, further out in the cache hierarchy we have caches with 128 byte lines. Those are the ones that matter for DMA safety. So we need the larger alignment guarantees of ARCH_KMALLOC_MINALIGN which in this case is 128 bytes. There is one other use of ____cacheline_aligned in input: joystick/iforce/iforce-usb.c Whilst suspicious I'm not sure enough of the requirements of USB to know if they are there for DMA safety or some other constraint. Jonathan Cc: Daniel Mack <daniel@xxxxxxxxxx> Cc: Michael Hennerich <michael.hennerich@xxxxxxxxxx> Cc: Tomohiro Yoshidomi <sylph23k@xxxxxxxxx> Cc: Javier Martinez Canillas <javier@xxxxxxxxxxxx> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> Cc: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> Cc: Lauri Kasanen <cand@xxxxxxx> Cc: Daniel Hung-yu Wu <hywu@xxxxxxxxxx> Jonathan Cameron (9): Input: psxpad - Fix padding for DMA safe buffers. Input: ad714x - Fix padding for DMA safe buffers. Input: ad7887 - Fix padding for DMA safe buffers. Input: ads7846 - Fix padding for DMA safe buffers. Input: cyttsp - Fix padding for DMA safe buffers. Input: surface3 - Fix padding for DMA safe buffers. Input: n64joy - Fix DMA buffer alignment. Input: atmel_captouch - Avoid suspect DMA buffer alignment. Input: elants - Fix suspect DMA buffer alignment drivers/input/joystick/n64joy.c | 6 +++--- drivers/input/joystick/psxpad-spi.c | 4 ++-- drivers/input/misc/ad714x.h | 2 +- drivers/input/misc/atmel_captouch.c | 2 +- drivers/input/touchscreen/ad7877.c | 4 ++-- drivers/input/touchscreen/ads7846.c | 4 ++-- drivers/input/touchscreen/cyttsp_core.h | 2 +- drivers/input/touchscreen/elants_i2c.c | 2 +- drivers/input/touchscreen/surface3_spi.c | 2 +- 9 files changed, 14 insertions(+), 14 deletions(-) -- 2.38.1
