# Re: \[RFC PATCH v3 2/6\] swiotlb: Add restricted DMA pool

- From: Konrad Rzeszutek Wilk \<hidden\>
- Date: 2021-01-06 18:55:23 
- List: linux-devicetree
- Page: https://ratatoskr.run/linux-devicetree/2021/01/6225757
- Thread: https://ratatoskr.run/linux-devicetree/2021/01/6224988/t.md

```text
Hello!

In this file:

> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index e4368159f88a..7fb2ac087d23 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
..

> +static const struct reserved_mem_ops rmem_swiotlb_ops = {
> +	.device_init	= rmem_swiotlb_device_init,
> +	.device_release	= rmem_swiotlb_device_release,
> +};
> +
> +static int __init rmem_swiotlb_setup(struct reserved_mem *rmem)
> +{
> +	unsigned long node = rmem->fdt_node;
> +
> +	if (of_get_flat_dt_prop(node, "reusable", NULL) ||
> +	    of_get_flat_dt_prop(node, "linux,cma-default", NULL) ||
> +	    of_get_flat_dt_prop(node, "linux,dma-default", NULL) ||
> +	    of_get_flat_dt_prop(node, "no-map", NULL))
> +		return -EINVAL;
> +
> +	rmem->ops = &rmem_swiotlb_ops;
> +	pr_info("Reserved memory: created device swiotlb memory pool at %pa, size %ld MiB\n",
> +		&rmem->base, (unsigned long)rmem->size / SZ_1M);
> +	return 0;
> +}
> +
> +RESERVEDMEM_OF_DECLARE(dma, "restricted-dma-pool", rmem_swiotlb_setup);

The code should be as much as possible arch-agnostic. That is why there
are multiple -swiotlb files scattered in arch directories that own the
architecture specific code.

Would it be possible to move the code there and perhaps have a ARM
specific front-end for this DMA restricted pool there? See for example
the xen-swiotlb code.

Cheers!

Konrad
```