Re: [RFC 1/3] dt-bindings: dma: Add documentation for DMA domains

Peter Ujfalusi
2019-09-08T07:47:48Z

On 06/09/2019 17.18, Peter Ujfalusi wrote:
> On systems where multiple DMA controllers available, none Slave (for example
> memcpy operation) users can not be described in DT as there is no device
> involved from the DMA controller's point of view, DMA binding is not usable.
> However in these systems still a peripheral might need to be serviced by or
> it is better to serviced by specific DMA controller.
> When a memcpy is used to/from a memory mapped region for example a DMA in the
> same domain can perform better.
> For generic software modules doing mem 2 mem operations it also matter that
> they will get a channel from a controller which is faster in DDR to DDR mode
> rather then from the first controller happen to be loaded.
>
> This property is inherited, so it may be specified in a device node or in any
> of its parent nodes.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
> .../devicetree/bindings/dma/dma-domain.yaml | 59 +++++++++++++++++++
> 1 file changed, 59 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/dma/dma-domain.yaml
>
> diff --git a/Documentation/devicetree/bindings/dma/dma-domain.yaml b/Documentation/devicetree/bindings/dma/dma-domain.yaml
> new file mode 100644
> index 000000000000..c2f182f30081
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/dma-domain.yaml
> @@ -0,0 +1,59 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/dma-controller.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: DMA Domain Controller Definition
> +
> +maintainers:
> + - Vinod Koul <vkoul@kernel.org>
> +
> +allOf:
> + - $ref: "dma-controller.yaml#"
> +
> +description:
> + On systems where multiple DMA controllers available, none Slave (for example
> + memcpy operation) users can not be described in DT as there is no device
> + involved from the DMA controller's point of view, DMA binding is not usable.
> + However in these systems still a peripheral might need to be serviced by or
> + it is better to serviced by specific DMA controller.
> + When a memcpy is used to/from a memory mapped region for example a DMA in the
> + same domain can perform better.
> + For generic software modules doing mem 2 mem operations it also matter that
> + they will get a channel from a controller which is faster in DDR to DDR mode
> + rather then from the first controller happen to be loaded.
> +
> + This property is inherited, so it may be specified in a device node or in any
> + of its parent nodes.
> +
> +properties:
> + $dma-domain-controller:

or domain-dma-controller?

> + $ref: /schemas/types.yaml#definitions/phandle
> + description:
> + phande to the DMA controller node which should be used for the device or
> + domain.
> +
> +examples:
> + - |
> + / {
> + model = "Texas Instruments K3 AM654 SoC";
> + compatible = "ti,am654";
> + interrupt-parent = <&gic500>;
> + /* For modules without device, DDR to DDR is faster on main UDMAP */
> + dma-domain-controller = <&main_udmap>;
> + #address-cells = <2>;
> + #size-cells = <2>;
> + ...
> + };
> +
> + &cbass_main {
> + /* For modules within MAIN domain, use main UDMAP */
> + dma-domain-controller = <&main_udmap>;
> + };
> +
> + &cbass_mcu {
> + /* For modules within MCU domain, use mcu UDMAP */
> + dma-domain-controller = <&mcu_udmap>;
> + };
> +...
>

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