Re: [PATCH v3 4/7] of: address: Add support for the parent DMA bus

From: Robin Murphy <robin.murphy@arm.com>
To: Maxime Ripard <maxime.ripard@bootlin.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Chen-Yu Tsai <wens@csie.org>
Cc: devicetree@vger.kernel.org, Yong Deng <yong.deng@magewell.com>,
	Arnd Bergmann <arnd@arndb.de>,
	dri-devel@lists.freedesktop.org,
	Dave Martin <dave.martin@arm.com>,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Georgi Djakov <georgi.djakov@linaro.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 4/7] of: address: Add support for the parent DMA bus
Date: Tue, 12 Feb 2019 18:15:13 +0000	[thread overview]
Message-ID: <25d076ef-60a9-b424-878b-d8066e907b35@arm.com> (raw)
In-Reply-To: <fc76568f10be15b0dfc7515d6affecb20de3e479.1549897336.git-series.maxime.ripard@bootlin.com>

On 11/02/2019 15:02, 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.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
>   drivers/of/address.c | 34 +++++++++++++++++++++++++++++++---
>   1 file changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 4c5dc21c71ca..0e9d87a664f5 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -583,8 +583,8 @@ static u64 __of_translate_address(struct device_node *dev,
>   	/* Increase refcount at current level */
>   	of_node_get(dev);
>   
> +	*host = NULL;
>   	if (!parent) {
> -		*host = NULL;
>   		/* Get parent & match bus type */
>   		parent = of_get_parent(dev);
>   		if (parent == NULL)
> @@ -678,12 +678,34 @@ 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(struct device_node *np)
> +{
> +	struct of_phandle_args args;
> +	unsigned int index;
> +	int ret;
> +
> +	ret = of_property_match_string(np, "interconnect-names", "dma");
> +	if (ret < 0)
> +		return of_get_parent(np);

Don't you need to propagate ret to index here?

Robin.

> +
> +	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 *parent;
>   	struct device_node *host;
>   	u64 ret;
>   
> -	ret = __of_translate_address(dev, NULL, in_addr, "dma-ranges", &host);
> +	parent = __of_get_dma_parent(dev);
> +	ret = __of_translate_address(dev, parent, in_addr, "dma-ranges", &host);
> +	of_node_put(parent);
>   
>   	if (host) {
>   		of_node_put(host);
> @@ -911,9 +933,15 @@ 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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