Date:   Wed, 22 Feb 2023 14:50:36 +0000
From:   Conor Dooley <conor@kernel.org>
To:     Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc:     linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, tsbogend@alpha.franken.de,
        mpe@ellerman.id.au, paul.walmsley@sifive.com, palmer@dabbelt.com,
        robh+dt@kernel.org, hch@lst.de, m.szyprowski@samsung.com,
        robin.murphy@arm.com, linux-riscv@lists.infradead.org
Subject: Re: [PATCH 2/3] riscv: Set dma_default_coherent to true
Message-ID: <Y/YrvDBJcYUQt4WC@spud>
References: <20230222133712.8079-1-jiaxun.yang@flygoat.com>
 <20230222133712.8079-3-jiaxun.yang@flygoat.com>
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On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote:
> For riscv our assumption is unless a device states it is non-coherent,
> we take it to be DMA coherent.
>=20
> For devicetree probed devices that have been true since very begining
> with OF_DMA_DEFAULT_COHERENT selected.
>=20
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>  arch/riscv/kernel/setup.c | 3 +++
>  1 file changed, 3 insertions(+)
>=20
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 376d2827e736..34b371180976 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p)
>  	riscv_init_cbom_blocksize();
>  	riscv_fill_hwcap();
>  	apply_boot_alternatives();
> +#ifdef CONFIG_RISCV_DMA_NONCOHERENT
> +	dma_default_coherent =3D true;
> +#endif

Do we really need to add ifdeffery for this here?
It's always coherent by default, so why do we need to say set it in
setup_arch() when we know that, regardless of options, it is true?

Cheers,
Conor.

>  	if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) &&
>  	    riscv_isa_extension_available(NULL, ZICBOM))
>  		riscv_noncoherent_supported();
> --=20
> 2.37.1 (Apple Git-137.1)
>=20

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