linux-kernel - Re: [PATCH v13 6/8] media: dt-bindings: wave5: add Chips&Media 521c codec IP support

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Date:   Sat, 21 Oct 2023 13:53:40 +0200
From:   Sebastian Fricke <sebastian.fricke@...labora.com>
To:     Devarsh Thakkar <devarsht@...com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        NXP Linux Team <linux-imx@....com>,
        Conor Dooley <conor+dt@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jackson Lee <jackson.lee@...psnmedia.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Nas Chung <nas.chung@...psnmedia.com>,
        Fabio Estevam <festevam@...il.com>,
        linux-media@...r.kernel.org, Tomasz Figa <tfiga@...omium.org>,
        linux-kernel@...r.kernel.org,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        kernel@...labora.com, Robert Beckett <bob.beckett@...labora.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Darren Etheridge <detheridge@...com>,
        "Bajjuri, Praneeth" <praneeth@...com>,
        "Raghavendra, Vignesh" <vigneshr@...com>,
        "Bhatia, Aradhya" <a-bhatia1@...com>,
        "Luthra, Jai" <j-luthra@...com>,
        "Brnich, Brandon" <b-brnich@...com>,
        "Pothukuchi, Vijay" <vijayp@...com>
Subject: Re: [PATCH v13 6/8] media: dt-bindings: wave5: add Chips&Media 521c
 codec IP support

Hello Krzysztof and Rob,

this question is quite important for our next version and for the
overall direction of the DT bindings, could you have a look at this?

Thank you and Regards,
Sebastian

On 17.10.2023 19:09, Devarsh Thakkar wrote:
>Hi Sebastian, Krzysztof, Rob,
>
>On 12/10/23 16:31, Sebastian Fricke wrote:
>> From: Robert Beckett <bob.beckett@...labora.com>
>>
>> Add bindings for the chips&media wave5 codec driver
>>
>> Signed-off-by: Robert Beckett <bob.beckett@...labora.com>
>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@...labora.com>
>> Signed-off-by: Sebastian Fricke <sebastian.fricke@...labora.com>
>> ---
>>  .../devicetree/bindings/media/cnm,wave5.yaml       | 60 ++++++++++++++++++++++
>>  1 file changed, 60 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/media/cnm,wave5.yaml b/Documentation/devicetree/bindings/media/cnm,wave5.yaml
>> new file mode 100644
>> index 000000000000..b31d34aec05b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/media/cnm,wave5.yaml
>> @@ -0,0 +1,60 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/media/cnm,wave5.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Chips&Media Wave 5 Series multi-standard codec IP
>> +
>> +maintainers:
>> +  - Nas Chung <nas.chung@...psnmedia.com>
>> +  - Jackson Lee <jackson.lee@...psnmedia.com>
>> +
>> +description:
>> +  The Chips&Media WAVE codec IP is a multi format video encoder/decoder
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - cnm,cm521c-vpu
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  clocks:
>> +    items:
>> +      - description: VCODEC clock
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  power-domains:
>> +    maxItems: 1
>> +
>> +  resets:
>> +    maxItems: 1
>> +
>> +  sram:
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +    description:
>> +      The VPU uses the SRAM to store some of the reference data instead of
>> +      storing it on DMA memory. It is mainly used for the purpose of reducing
>> +      bandwidth.
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - clocks
>> +  - interrupts
>> +
>
>Is it possible to keep interrupts property as optional given HW can still work
>without it if SW does polling of ISR using registers?
>
>The reason to ask is in TI AM62A SoC (which also uses this codec) there is an
>SoC errata of missing interrupt line to A53 and we are using SW based polling
>locally to run the driver.
>
>We were planning to upstream that SW based polling support patch in CnM driver
>once this base initial driver patch series gets merged, but just wanted to
>check if upfront it is possible to have interrupts property as optional so
>that we don't have to change the binding doc again to make it optional later on.
>
>Also note that the polling patch won't be specific to AM62A, other SoC's too
>which use this wave5 hardware if they want can enable polling by choice (by
>removing interrupt property)
>
>Could you please share your opinion on this ?
>
>Regards
>Devarsh
>
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    vpu: video-codec@...45678 {
>> +        compatible = "cnm,cm521c-vpu";
>> +        reg = <0x12345678 0x1000>;
>> +        clocks = <&clks 42>;
>> +        interrupts = <42>;
>> +        sram = <&sram>;
>> +    };
>>
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