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Subject: Re: [PATCH v2 5/5] of: address: Always use dma_default_coherent for
 default coherency
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
In-Reply-To: <20230301130613.GC467@lst.de>
Date:   Wed, 1 Mar 2023 14:18:10 +0000
Cc:     "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        mpe@ellerman.id.au, paul.walmsley@sifive.com, palmer@dabbelt.com,
        Rob Herring <robh+dt@kernel.org>, m.szyprowski@samsung.com,
        robin.murphy@arm.com, linux-riscv@lists.infradead.org
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Message-Id: <B43602D1-89D4-465F-83B1-CD106E07CB29@flygoat.com>
References: <20230223113644.23356-1-jiaxun.yang@flygoat.com>
 <20230223113644.23356-6-jiaxun.yang@flygoat.com>
 <20230301130613.GC467@lst.de>
To:     Christoph Hellwig <hch@lst.de>
Precedence: bulk


> 2023=E5=B9=B43=E6=9C=881=E6=97=A5 13:06=EF=BC=8CChristoph Hellwig =
<hch@lst.de> =E5=86=99=E9=81=93=EF=BC=9A
>=20
>> - select OF_DMA_DEFAULT_COHERENT if !NOT_COHERENT_CACHE
>=20
> Doesn't powerpc need to select CONFIG_ARCH_DMA_DEFAULT_COHERENT now,
> or even better should be doing that in the patch adding that
> symbol?

If I read the code correctly for powerpc OF_DMA_DEFAULT_COHERENT is only =
selected
with !NOT_COHERENT_CACHE, which means non-coherent dma support is =
disabled=E2=80=A6.

>=20
> In fact I wonder if adding CONFIG_ARCH_DMA_DEFAULT_COHERENT and =
removing
> OF_DMA_DEFAULT_COHERENT should be one patch, as that seems to bring
> over the intent a little better I'd say.