Date: Mon, 3 Apr 2017 14:37:05 +0100 From: Andrew Turner <andrew@fubar.geek.nz> To: Marcin Wojtas <mw@semihalf.com> Cc: Adrian Chadd <adrian.chadd@gmail.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: Coherent bus_dma for ARMv7 Message-ID: <0EA39E6B-3460-45B9-8247-CB6CC8631C5F@fubar.geek.nz> In-Reply-To: <CAPv3WKez8ZP=xONvPWGiyL5pQDKO4wGF_qQn=eT1S_LzrGJ74g@mail.gmail.com> References: <CAPv3WKejupH4JG1=_XV6PknnKifxbF0qoVubtMRVtZWEoBZ7xg@mail.gmail.com> <CAPv3WKcG_Y=5zPk-2vGbQfCpiNcWvuUymY8EHRnWsM2FUzcG4Q@mail.gmail.com> <CAJ-Vmo=UC9K3e0TJGU86JZ6npzRevjpC3UEwgWrrh9mjCELKMg@mail.gmail.com> <CAPv3WKez8ZP=xONvPWGiyL5pQDKO4wGF_qQn=eT1S_LzrGJ74g@mail.gmail.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
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