Hi Jonathan,
> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> Sent: Tuesday, May 3, 2022 10:58 AM
> To: linux-iio@xxxxxxxxxxxxxxx
> Cc: Akinobu Mita <akinobu.mita@xxxxxxxxx>; Alexandru Lazar
> <alazar@xxxxxxxxxxxxx>; Tachici, Alexandru
> <Alexandru.Tachici@xxxxxxxxxx>; Miclaus, Antoniu
> <Antoniu.Miclaus@xxxxxxxxxx>; Charles-Antoine Couret <charles-
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> Ivan Mikhaylov <i.mikhaylov@xxxxxxxxx>; Jacopo Mondi
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> <lars@xxxxxxxxxx>; Marcelo Schmitt <marcelo.schmitt1@xxxxxxxxx>;
> Mårten Lindahl <martenli@xxxxxxxx>; Matt Ranostay
> <mranostay@xxxxxxxxx>; Hennerich, Michael
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> <mwelling@xxxxxxxx>; Mugilraj Dhavachelvan
> <dmugil2000@xxxxxxxxx>; Navin Sankar Velliangiri
> <navin@xxxxxxxxxxx>; Sa, Nuno <Nuno.Sa@xxxxxxxxxx>; Paul
> Cercueil <paul@xxxxxxxxxxxxxxx>; Phil Reid
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> Robert Jones <rjones@xxxxxxxxxxxxx>; Rui Miguel Silva
> <rui.silva@xxxxxxxxxx>; Sean Nyekjaer <sean.nyekjaer@xxxxxxxxx>;
> Tomas Melin <tomas.melin@xxxxxxxxxxx>; Tomislav Denis
> <tomislav.denis@xxxxxxx>; Uwe Kleine-König <u.kleine-
> koenig@xxxxxxxxxxxxxx>; Jonathan Cameron
> <Jonathan.Cameron@xxxxxxxxxx>; catalin.marinas@xxxxxxx
> Subject: [PATCH 00/92] IIO: Fix alignment of buffers for DMA
>
> [External]
>
> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>
> Many years ago, IIO started using ____cacheline_aligned to ensure
> that buffers that might be used for DMA were not sharing a cacheline
> with other data that might lead to DMA safety issues.
>
> As it turns out, that was fine at the time, but not based on the
> correct alignment requirement (though I believe it was a conservative
> choice at the time). Note that on many architectures this was
> introducing
> unecessary padding. We should have been using
> ARCH_KMALLOC_MINALIGN
> as other subsystems such as crypto have done for a long time.
>
> Patch 1 discription contains more information but in short, there are
> ARM64 SoCs out their that have a larger cachline size for caches
> beyond
> L1. In many cases they maintain coherency for all DMA devices
> attached
> and so this isn't a problem, but there are exceptions that do not.
>
> So, this is a rather large patch set and just covers those drivers
> that are in the last kernel release and in drivers/iio.
>
> Many of these drivers are somewhat old so I haven't specifically
> cc'd anyone so will be relying on those kind enough to sanity check
> patches on drivers that are beyond their own.
>
> Given there is ongoing discussion around reducing the alignment
> requirements where possible, I've adopted the existing IIO_ALIGN
> define througout. That way we have a single point to update if
> that becomes relevant in future.
>
Nice to see this in... Since we are here, I guess in a couple of patches where we have:
struct {
...
u8 rx[] __aligned();
u8 tx[] __aligned();
};
we could make it such that only the first member is aligned. But bah, I get that this
is already a huge patchset to diverge from it. Anyhow,
Acked-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
