linux-kernel - Re: [PATCH v5 1/2] dt-bindings: dma: Add bindings for intel LGM SOC

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Date:   Thu, 27 Aug 2020 17:54:28 +0800
From:   "Reddy, MallikarjunaX" <mallikarjunax.reddy@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Rob Herring <robh@...nel.org>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        andriy.shevchenko@...el.com, cheol.yong.kim@...el.com,
        qi-ming.wu@...el.com, chuanhua.lei@...ux.intel.com,
        malliamireddy009@...il.com
Subject: Re: [PATCH v5 1/2] dt-bindings: dma: Add bindings for intel LGM SOC

Hi Vinod,
Thanks for the review comments.

On 8/25/2020 7:21 PM, Vinod Koul wrote:
> On 18-08-20, 15:00, Reddy, MallikarjunaX wrote:
>
>>>> +
>>>> +            intel,chans:
>>>> +              $ref: /schemas/types.yaml#/definitions/uint32-array
>>>> +              description:
>>>> +                 The channels included on this port. Format is channel start
>>>> +                 number and how many channels on this port.
>>> Why does this need to be in DT? This all seems like it can be in the dma
>>> cells for each client.
>> (*ABC)
>> Yes. We need this.
>> for dma0(lgm-cdma) old SOC supports 16 channels and the new SOC supports 22
>> channels. and the logical channel mapping for the peripherals also differ
>> b/w old and new SOCs.
>>
>> Because of this hardware limitation we are trying to configure the total
>> channels and port-channel mapping dynamically from device tree.
>>
>> based on port name we are trying to configure the default values for
>> different peripherals(ports).
>> Example: burst length is not same for all ports, so using port name to do
>> default configurations.
> Sorry that does not make sense to me, why not specify the values to be
> used here instead of defining your own name scheme!
OK. Agreed. I will remove port name from DT and only use intel,chans
>
> Only older soc it should create 16 channels and new 22 (hint this is hw
> description so perfectly okay to specify in DT or in using driver_data
> and compatible for each version
>
>>>> +
>>>> +          required:
>>>> +            - reg
>>>> +            - intel,name
>>>> +            - intel,chans
>>>> +
>>>> +
>>>> + ldma-channels:
>>>> +    type: object
>>>> +    description:
>>>> +       This sub-node must contain a sub-node for each DMA channel.
>>>> +    properties:
>>>> +      '#address-cells':
>>>> +        const: 1
>>>> +      '#size-cells':
>>>> +        const: 0
>>>> +
>>>> +    patternProperties:
>>>> +      "^ldma-channels@[0-15]+$":
>>>> +          type: object
>>>> +
>>>> +          properties:
>>>> +            reg:
>>>> +              items:
>>>> +                - enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
>>>> +              description:
>>>> +                 Which channel this node refers to.
>>>> +
>>>> +            intel,desc_num:
>>>> +              $ref: /schemas/types.yaml#/definitions/uint32
>>>> +              description:
>>>> +                 Per channel maximum descriptor number. The max value is 255.
>>>> +
>>>> +            intel,hdr-mode:
>>>> +              $ref: /schemas/types.yaml#/definitions/uint32-array
>>>> +              description:
>>>> +                 The first parameter is header mode size, the second
>>>> +                 parameter is checksum enable or disable. If enabled,
>>>> +                 header mode size is ignored. If disabled, header mode
>>>> +                 size must be provided.
>>>> +
>>>> +            intel,hw-desc:
>>>> +              $ref: /schemas/types.yaml#/definitions/uint32-array
>>>> +              description:
>>>> +                 Per channel dma hardware descriptor configuration.
>>>> +                 The first parameter is descriptor physical address and the
>>>> +                 second parameter hardware descriptor number.
>>> Again, this all seems like per client information for dma cells.
>>   Ok, if we move all these attributes to 'dmas' then 'dma-channels' child
>> node is not needed in dtsi.
>> #dma-cells number i am already using 7. If we move all these attributes to
>> 'dmas' then integer cells will increase.
>>
>> Is there any limitation in using a number of integer cells & as determined
>> by the #dma-cells property?
> No I dont think there is but it needs to make sense :-)
OK.
>