Re: [RFC 2/3] dmaengine: of_dma: Function to look up the DMA domain of a client

Vinod Koul
2019-09-08T12:13:43Z

On 06-09-19, 17:18, Peter Ujfalusi wrote:
> Find the DMA domain controller of the client device by iterating up in
> device tree looking for the closest 'dma-domain-controller' property.
>
> If the client's node is not provided then check the DT root for the
> controller.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
> drivers/dma/of-dma.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/of_dma.h | 7 +++++++
> 2 files changed, 49 insertions(+)
>
> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> index c2d779daa4b5..04b5795cd76b 100644
> --- a/drivers/dma/of-dma.c
> +++ b/drivers/dma/of-dma.c
> @@ -18,6 +18,48 @@
> static LIST_HEAD(of_dma_list);
> static DEFINE_MUTEX(of_dma_lock);
>
> +/**
> + * of_find_dma_domain - Get the domain DMA controller
> + * @np: device node of the client device
> + *
> + * Look up the DMA controller of the domain the client device is part of.
> + * Finds the dma-domain controller the client device belongs to. It is used when
> + * requesting non slave channels (like channel for memcpy) to make sure that the
> + * channel can be request from a DMA controller which can service the given
> + * domain best.
> + *
> + * Returns the device_node pointer of the DMA controller or succes or NULL on
> + * error.
> + */
> +struct device_node *of_find_dma_domain(struct device_node *np)
> +{
> + struct device_node *dma_domain = NULL;
> + phandle dma_phandle;
> +
> + /*
> + * If no device_node is provided look at the root level for system
> + * default DMA controller for modules.
> + */
> + if (!np)
> + np = of_root;
> +
> + if (!np || !of_node_get(np))
> + return NULL;
> +
> + do {
> + if (of_property_read_u32(np, "dma-domain-controller",
> + &dma_phandle))
> + np = of_get_next_parent(np);

lets have braces around if as well please

> + else {
> + dma_domain = of_find_node_by_phandle(dma_phandle);
> + of_node_put(np);
> + }
> + } while (!dma_domain && np);
> +
> + return dma_domain;
> +}
> +EXPORT_SYMBOL_GPL(of_find_dma_domain);
> +
> /**
> * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
> * @dma_spec: pointer to DMA specifier as found in the device tree
> diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
> index fd706cdf255c..6eab0a8d3335 100644
> --- a/include/linux/of_dma.h
> +++ b/include/linux/of_dma.h
> @@ -32,6 +32,8 @@ struct of_dma_filter_info {
> };
>
> #ifdef CONFIG_DMA_OF
> +extern struct device_node *of_find_dma_domain(struct device_node *np);
> +
> extern int of_dma_controller_register(struct device_node *np,
> struct dma_chan *(*of_dma_xlate)
> (struct of_phandle_args *, struct of_dma *),
> @@ -52,6 +54,11 @@ extern struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec
> struct of_dma *ofdma);
>
> #else
> +static inline struct device_node *of_find_dma_domain(struct device_node *np)
> +{
> + return NULL;
> +}
> +
> static inline int of_dma_controller_register(struct device_node *np,
> struct dma_chan *(*of_dma_xlate)
> (struct of_phandle_args *, struct of_dma *),
> --
> Peter
>
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

--
~Vinod