# Re: \[PATCH V3 21/22\] LoongArch: Add Non-Uniform Memory Access (NUMA) support

- From: Christoph Hellwig \<hch@infradead.org\>
- Date: 2021-09-17 06:17:37 
- List: linux-doc
- Page: https://ratatoskr.run/linux-doc/2021/09/1512513
- Thread: https://ratatoskr.run/linux-arch/2021/09/1512437/t.md

```text
> +/*
> + * 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 

```