linux-kernel - Re: [PATCH 04/12] soc: sifive: ccache: Add non-coherent DMA handling

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Date:   Thu, 16 Feb 2023 18:50:22 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Richard Cochran <richardcochran@...il.com>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        Yanhong Wang <yanhong.wang@...rfivetech.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, kernel@...labora.com,
        daire.mcnamara@...rochip.com
Subject: Re: [PATCH 04/12] soc: sifive: ccache: Add non-coherent DMA handling

Emil,

+CC Daire

On Sat, Feb 11, 2023 at 05:18:13AM +0200, Cristian Ciocaltea wrote:
> From: Emil Renner Berthing <kernel@...il.dk>
> 
> Add functions to flush the caches and handle non-coherent DMA.
> 
> Signed-off-by: Emil Renner Berthing <kernel@...il.dk>
> [replace <asm/cacheflush.h> with <linux/cacheflush.h>]
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---

> +void *sifive_ccache_set_uncached(void *addr, size_t size)
> +{
> +	phys_addr_t phys_addr = __pa(addr) + uncached_offset;
> +	void *mem_base;
> +
> +	mem_base = memremap(phys_addr, size, MEMREMAP_WT);
> +	if (!mem_base) {
> +		pr_err("%s memremap failed for addr %p\n", __func__, addr);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return mem_base;
> +}

The rest of this I either get b/c we did it, or will become moot so I
amn't worried about it, but can you please explain this, in particular
the memremap that you're doing here?

Cheers,
Conor.


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