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Date:   Fri, 17 Sep 2021 07:15:28 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Huacai Chen <chenhuacai@loongson.cn>
Cc:     Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Xuefeng Li <lixuefeng@loongson.cn>,
        Yanteng Si <siyanteng@loongson.cn>,
        Huacai Chen <chenhuacai@gmail.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH V3 21/22] LoongArch: Add Non-Uniform Memory Access (NUMA)
 support
Message-ID: <YUQygKWFMU8zrkFi@infradead.org>
References: <20210917035736.3934017-1-chenhuacai@loongson.cn>
 <20210917035736.3934017-22-chenhuacai@loongson.cn>
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In-Reply-To: <20210917035736.3934017-22-chenhuacai@loongson.cn>
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> +/*
> + * We extract 4bit node id (bit 44~47) from Loongson-3's
> + * 48bit physical address space and embed it into 40bit.
> + */
> +
> +static int node_id_offset;
> +
> +static dma_addr_t loongson_phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	long nid = (paddr >> 44) & 0xf;
> +
> +	return ((nid << 44) ^ paddr) | (nid << node_id_offset);
> +}
> +
> +static phys_addr_t loongson_dma_to_phys(struct device *dev, dma_addr_t daddr)
> +{
> +	long nid = (daddr >> node_id_offset) & 0xf;
> +
> +	return ((nid << node_id_offset) ^ daddr) | (nid << 44);
> +}
> +
> +static struct loongson_addr_xlate_ops {
> +	dma_addr_t (*phys_to_dma)(struct device *dev, phys_addr_t paddr);
> +	phys_addr_t (*dma_to_phys)(struct device *dev, dma_addr_t daddr);
> +} xlate_ops;
> +
> +dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	return xlate_ops.phys_to_dma(dev, paddr);
> +}
> +
> +phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
> +{
> +	return xlate_ops.dma_to_phys(dev, daddr);
> +}

Please don't add unused indirections.  Also please just use the generic
translations