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Subject: Re: Coherent bus_dma for ARMv7
From: Andrew Turner <andrew@fubar.geek.nz>
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Date: Mon, 3 Apr 2017 14:37:05 +0100
Cc: Adrian Chadd <adrian.chadd@gmail.com>,
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To: Marcin Wojtas <mw@semihalf.com>
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> On 3 Apr 2017, at 14:16, Marcin Wojtas <mw@semihalf.com> wrote:
>=20
> Hi Adrian,
>=20
> Frankly we are not such experts in armv6 bus_dma, which looks more
> complicated than one in arm64, so we thought it's much safer no to mix
> the two solutions and leave for the user a single switch to decide,
> which one to pick. Afaik Andrew Turner did the oposite for arm64
> (implement not coherent solution on top of coherent bus_dma), however
> I'm not sure if it's possible here in an easy way - there's also
> pretty significant risk of regression for all platforms. Please let me
> know your opinion. Do you think some sort of update of armv6 is
> doable?

I don=E2=80=99t see any reason to think it would be difficult to add =
support for coherent hardware to the existing armv6 busdma code. It=E2=80=99=
s mostly skipping cache operations based on a flag in the dam tag.

Andrew