Re: [PATCH v4 4/7] of: address: Add support for the parent DMA bus

[Robin Murphy <robin.murphy@arm.com>]

On 14/03/2019 20:26, Maxime Ripard wrote:
> Some SoCs have devices that are using a separate bus from the main bus to
> perform DMA.
> 
> These buses might have some restrictions and/or different mapping than from
> the CPU side, so we'd need to express those using the usual dma-ranges, but
> using a different DT node than the node's parent.
> 
> Now that the generic interconnect bindings are available, we can model an
> interconnect with the reserved name "dma" for those use-cases.

Nit: it's "dma-mem" now.

> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
>   drivers/of/address.c | 29 ++++++++++++++++++++++++++---
>   1 file changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 140bd0718067..95e47f2e9198 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -678,14 +678,31 @@ u64 of_translate_address(struct device_node *dev, const __be32 *in_addr)
>   }
>   EXPORT_SYMBOL(of_translate_address);
>   
> +static struct device_node *__of_get_dma_parent(const struct device_node *np)
> +{
> +	struct of_phandle_args args;
> +	int ret, index;
> +
> +	index = of_property_match_string(np, "interconnect-names", "dma-mem");
> +	if (index < 0)
> +		return of_get_parent(np);
> +
> +	ret = of_parse_phandle_with_args(np, "interconnects",
> +					 "#interconnect-cells",
> +					 index, &args);
> +	if (ret < 0)
> +		return of_get_parent(np);
> +
> +	return of_node_get(args.np);
> +}
> +
>   u64 of_translate_dma_address(struct device_node *dev, const __be32 *in_addr)
>   {
>   	struct device_node *host;
>   	u64 ret;
>   
> -	ret = __of_translate_address(dev, of_get_parent,
> +	ret = __of_translate_address(dev, __of_get_dma_parent,
>   				     in_addr, "dma-ranges", &host);
> -

Nit: ideally patch #3 wouldn't introduce that blank line in the first place.

Otherwise,

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

>   	if (host) {
>   		of_node_put(host);
>   		return OF_BAD_ADDR;
> @@ -913,9 +930,15 @@ int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *siz
>   		return -EINVAL;
>   
>   	while (1) {
> +		struct device_node *parent;
> +
>   		naddr = of_n_addr_cells(node);
>   		nsize = of_n_size_cells(node);
> -		node = of_get_next_parent(node);
> +
> +		parent = __of_get_dma_parent(node);
> +		of_node_put(node);
> +
> +		node = parent;
>   		if (!node)
>   			break;
>   
> 
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