Re: [PATCH 1/3] dt-bindings: dma: Add YAML schemas for the generic DMA bindings

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

On 11.7.2019 20.33, Rob Herring wrote:
> On Thu, Jul 11, 2019 at 3:34 AM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
>>
>> The DMA controllers and consumers have a bunch of generic properties that
>> are needed in a device tree. Add a YAML schemas for those.
>>
>> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
>> ---
>>  .../devicetree/bindings/dma/dma-consumer.yaml |  60 +++++++++
> 
> This already exists in the dt-schema/schemas/dma/dma.yaml though not
> the descriptions because that needs relicensing.
> 
> Looks like we need NVidia's (Jon H) and TI's (Peter U) permission.

If I'm not mistaken the new license is GPL-2.0, if so I don't see any
issue, but I'll ask our legal to be sure.

And one comment for the change.

> 
>>  .../bindings/dma/dma-controller.yaml          |  79 ++++++++++++
>>  Documentation/devicetree/bindings/dma/dma.txt | 114 +-----------------
>>  3 files changed, 140 insertions(+), 113 deletions(-)
>>  create mode 100644 Documentation/devicetree/bindings/dma/dma-consumer.yaml
>>  create mode 100644 Documentation/devicetree/bindings/dma/dma-controller.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/dma/dma-consumer.yaml b/Documentation/devicetree/bindings/dma/dma-consumer.yaml
>> new file mode 100644
>> index 000000000000..2f6315863ad1
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/dma/dma-consumer.yaml
>> @@ -0,0 +1,60 @@
>> +# SPDX-License-Identifier: GPL-2.0
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/dma/dma-consumer.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: DMA Consumer Generic Binding
>> +
>> +maintainers:
>> +  - Vinod Koul <vkoul@kernel.org>
>> +
>> +select: true
>> +
>> +properties:
>> +  dmas:
>> +    description:
>> +      List of one or more DMA specifiers, each consisting of
>> +          - A phandle pointing to DMA controller node
>> +          - A number of integer cells, as determined by the
>> +            \#dma-cells property in the node referenced by phandle
>> +            containing DMA controller specific information. This
>> +            typically contains a DMA request line number or a
>> +            channel number, but can contain any data that is
>> +            required for configuring a channel.
>> +
>> +  dma-names:
>> +    description:
>> +      Contains one identifier string for each DMA specifier in the
>> +      dmas property. The specific strings that can be used are defined
>> +      in the binding of the DMA client device.  Multiple DMA
>> +      specifiers can be used to represent alternatives and in this
>> +      case the dma-names for those DMA specifiers must be identical
>> +      (see examples).
>> +
>> +dependencies:
>> +  dma-names: [ dmas ]
>> +
>> +examples:
>> +  - |
>> +    /* A device with one DMA read channel, one DMA write channel */
>> +    i2c1: i2c@1 {
>> +         /* ... */
>> +         dmas = <&dma 2>,      /* read channel */
>> +                <&dma 3>;      /* write channel */
>> +        dma-names = "rx", "tx";
>> +        /* ... */
>> +    };
>> +
>> +  - |
>> +    /* A single read-write channel with three alternative DMA controllers */
>> +    dmas = <&dma1 5>, <&dma2 7>, <&dma3 2>;
>> +    dma-names = "rx-tx", "rx-tx", "rx-tx";
>> +
>> +  - |
>> +    /* A device with three channels, one of which has two alternatives */
>> +    dmas = <&dma1 2>,          /* read channel */
>> +           <&dma1 3>,          /* write channel */
>> +           <&dma2 0>,          /* error read */
>> +           <&dma3 0>;          /* alternative error read */
>> +    dma-names = "rx", "tx", "error", "error";
>> diff --git a/Documentation/devicetree/bindings/dma/dma-controller.yaml b/Documentation/devicetree/bindings/dma/dma-controller.yaml
>> new file mode 100644
>> index 000000000000..17c650131b78
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/dma/dma-controller.yaml
>> @@ -0,0 +1,79 @@
>> +# 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 Controller Generic Binding
>> +
>> +maintainers:
>> +  - Vinod Koul <vkoul@kernel.org>
>> +
>> +description:
>> +  Generic binding to provide a way for a driver using DMA Engine to
>> +  retrieve the DMA request or channel information that goes from a
>> +  hardware device to a DMA controller.
>> +
>> +properties:
>> +  $nodename:
>> +    pattern: "^dma-controller(@.*)?$"
>> +
>> +  "#dma-cells":
>> +    # minimum: 1
>> +    description:
>> +      Used to provide DMA controller specific information.
>> +
>> +  dma-channel-masks:
>> +    $ref: /schemas/types.yaml#definitions/uint32
>> +    description:
>> +      Bitmask of available DMA channels in ascending order that are
>> +      not reserved by firmware and are available to the
>> +      kernel. i.e. first channel corresponds to LSB.
>> +
>> +  dma-channels:
>> +    $ref: /schemas/types.yaml#definitions/uint32
>> +    description:
>> +      Number of DMA channels supported by the controller.
>> +
>> +  dma-masters:
>> +    $ref: /schemas/types.yaml#definitions/phandle-array
>> +    description:
>> +      DMA routers are transparent IP blocks used to route DMA request
>> +      lines from devices to the DMA controller. Some SoCs (like TI
>> +      DRA7x) have more peripherals integrated with DMA requests than
>> +      what the DMA controller can handle directly.
>> +
>> +      In such a case, dma-masters is an array of phandle to the DMA
>> +      controllers the router can direct the signal to.

It is no longer clear what is needed and what is optional anymore and if
I would need to look up how a DMA router node should look like I will be
in trouble, iow if I need to figure out how to describe an SoC with DMA
controller and DMA event router.

>> +
>> +  dma-requests:
>> +    $ref: /schemas/types.yaml#definitions/uint32
>> +    description:
>> +      Number of DMA request signals supported by the controller.
>> +
>> +examples:
>> +  - |
>> +    dma: dma@48000000 {
> 
> dma-controller@...
> 
> This is a case where I'd like some check that the schema is actually
> applied to the schema's example.
> 
>> +        compatible = "ti,omap-sdma";
>> +        reg = <0x48000000 0x1000>;
>> +        interrupts = <0 12 0x4
>> +                      0 13 0x4
>> +                      0 14 0x4
>> +                      0 15 0x4>;
>> +        #dma-cells = <1>;
>> +        dma-channels = <32>;
>> +        dma-requests = <127>;
>> +        dma-channel-mask = <0xfffe>;
>> +    };
>> +
>> +  - |
>> +    sdma_xbar: dma-router@4a002b78 {
>> +        compatible = "ti,dra7-dma-crossbar";
>> +        reg = <0x4a002b78 0xfc>;
>> +        #dma-cells = <1>;
>> +        dma-requests = <205>;
>> +        ti,dma-safe-map = <0>;
>> +        dma-masters = <&sdma>;
>> +    };
>> +
>> +...
>> diff --git a/Documentation/devicetree/bindings/dma/dma.txt b/Documentation/devicetree/bindings/dma/dma.txt
>> index eeb4e4d1771e..90a67a016a48 100644
>> --- a/Documentation/devicetree/bindings/dma/dma.txt
>> +++ b/Documentation/devicetree/bindings/dma/dma.txt
>> @@ -1,113 +1 @@
>> -* Generic DMA Controller and DMA request bindings
>> -
>> -Generic binding to provide a way for a driver using DMA Engine to retrieve the
>> -DMA request or channel information that goes from a hardware device to a DMA
>> -controller.
>> -
>> -
>> -* DMA controller
>> -
>> -Required property:
>> -- #dma-cells:          Must be at least 1. Used to provide DMA controller
>> -                       specific information. See DMA client binding below for
>> -                       more details.
>> -
>> -Optional properties:
>> -- dma-channels:        Number of DMA channels supported by the controller.
>> -- dma-requests:        Number of DMA request signals supported by the
>> -                       controller.
>> -- dma-channel-mask:    Bitmask of available DMA channels in ascending order
>> -                       that are not reserved by firmware and are available to
>> -                       the kernel. i.e. first channel corresponds to LSB.
>> -
>> -Example:
>> -
>> -       dma: dma@48000000 {
>> -               compatible = "ti,omap-sdma";
>> -               reg = <0x48000000 0x1000>;
>> -               interrupts = <0 12 0x4
>> -                             0 13 0x4
>> -                             0 14 0x4
>> -                             0 15 0x4>;
>> -               #dma-cells = <1>;
>> -               dma-channels = <32>;
>> -               dma-requests = <127>;
>> -               dma-channel-mask = <0xfffe>
>> -       };
>> -
>> -* DMA router
>> -
>> -DMA routers are transparent IP blocks used to route DMA request lines from
>> -devices to the DMA controller. Some SoCs (like TI DRA7x) have more peripherals
>> -integrated with DMA requests than what the DMA controller can handle directly.
>> -
>> -Required property:
>> -- dma-masters:         phandle of the DMA controller or list of phandles for
>> -                       the DMA controllers the router can direct the signal to.
>> -- #dma-cells:          Must be at least 1. Used to provide DMA router specific
>> -                       information. See DMA client binding below for more
>> -                       details.
>> -
>> -Optional properties:
>> -- dma-requests:        Number of incoming request lines the router can handle.
>> -- In the node pointed by the dma-masters:
>> -       - dma-requests: The router driver might need to look for this in order
>> -                       to configure the routing.
>> -
>> -Example:
>> -       sdma_xbar: dma-router@4a002b78 {
>> -               compatible = "ti,dra7-dma-crossbar";
>> -               reg = <0x4a002b78 0xfc>;
>> -               #dma-cells = <1>;
>> -               dma-requests = <205>;
>> -               ti,dma-safe-map = <0>;
>> -               dma-masters = <&sdma>;
>> -       };
>> -
>> -* DMA client
>> -
>> -Client drivers should specify the DMA property using a phandle to the controller
>> -followed by DMA controller specific data.
>> -
>> -Required property:
>> -- dmas:                        List of one or more DMA specifiers, each consisting of
>> -                       - A phandle pointing to DMA controller node
>> -                       - A number of integer cells, as determined by the
>> -                         #dma-cells property in the node referenced by phandle
>> -                         containing DMA controller specific information. This
>> -                         typically contains a DMA request line number or a
>> -                         channel number, but can contain any data that is
>> -                         required for configuring a channel.
>> -- dma-names:           Contains one identifier string for each DMA specifier in
>> -                       the dmas property. The specific strings that can be used
>> -                       are defined in the binding of the DMA client device.
>> -                       Multiple DMA specifiers can be used to represent
>> -                       alternatives and in this case the dma-names for those
>> -                       DMA specifiers must be identical (see examples).
>> -
>> -Examples:
>> -
>> -1. A device with one DMA read channel, one DMA write channel:
>> -
>> -       i2c1: i2c@1 {
>> -               ...
>> -               dmas = <&dma 2          /* read channel */
>> -                       &dma 3>;        /* write channel */
>> -               dma-names = "rx", "tx";
>> -               ...
>> -       };
>> -
>> -2. A single read-write channel with three alternative DMA controllers:
>> -
>> -       dmas = <&dma1 5
>> -               &dma2 7
>> -               &dma3 2>;
>> -       dma-names = "rx-tx", "rx-tx", "rx-tx";
>> -
>> -3. A device with three channels, one of which has two alternatives:
>> -
>> -       dmas = <&dma1 2                 /* read channel */
>> -               &dma1 3                 /* write channel */
>> -               &dma2 0                 /* error read */
>> -               &dma3 0>;               /* alternative error read */
>> -       dma-names = "rx", "tx", "error", "error";
>> +This file has been moved to dma-controller.yaml.
>> --
>> 2.21.0
>>

-- 
Peter

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