linux-kernel - Re: [PATCH v5 1/3] dt-bindings: media: imx-jpeg: Assign slot for imx jpeg encoder/decoder

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Message-ID: <d640f5c2-8af5-4402-a981-0e962d4f2aca@linaro.org>
Date:   Thu, 19 Oct 2023 09:19:09 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     "Ming Qian (OSS)" <ming.qian@....nxp.com>,
        mirela.rabulea@....nxp.com, robh+dt@...nel.org, shawnguo@...nel.org
Cc:     krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        mchehab@...nel.org, hverkuil-cisco@...all.nl,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        xiahong.bao@....com, eagle.zhou@....com, tao.jiang_2@....com,
        ming.qian@....com, linux-imx@....com, devicetree@...r.kernel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 1/3] dt-bindings: media: imx-jpeg: Assign slot for imx
 jpeg encoder/decoder

On 19/10/2023 04:48, Ming Qian (OSS) wrote:
> From: Ming Qian <ming.qian@....com>
> 
> This IP includes a jpeg wrapper and a jpeg engine, the wrapper is
> working on descriptor based manner. It supports up to 4 slots, each slot
> can have its own chained descriptors. Host won't configure the engine
> directly, but fill some descriptors to encode or decode one jpeg
> picture. Then configure the descriptors to certain slot register. The
> jpeg wrapper will schedule between different slots. When some slot is
> finished, the slot interrupt will be triggered. The purpose of slot is
> that engine can be shared across multiple VMS and os.
> 
> Currently, power domains and interrupts are enabled for all 4 slots, but
> only one slot is used. There is no benefit in using more that one slot
> from within the same OS, as the slots are scheduled in round-robin
> manner and not executed in parallel.
> 
> Use the property "nxp,slot" to assign a single slot, and just expose the
> parts of the h/w for the assigned slot. For example, only put slot 1's
> power-domains entry in the DT when slot 1 is assigned. If not specified,
> 0 is used by default.
> 
> Signed-off-by: Ming Qian <ming.qian@....com>
> ---
> v5
> - improve commit message
> - improve property description
> 
> v4
> - improve commit message
> - drop line making the property required, to avoid ABI break
> 
> v3
> - add vender prefix, change property slot to nxp,slot
> - add type for property slot
> 
> v2
> - add a new property in bindings document
> 
>  .../bindings/media/nxp,imx8-jpeg.yaml         | 46 +++++++++----------
>  1 file changed, 22 insertions(+), 24 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/nxp,imx8-jpeg.yaml b/Documentation/devicetree/bindings/media/nxp,imx8-jpeg.yaml
> index 3d9d1db37040..0961856bdcab 100644
> --- a/Documentation/devicetree/bindings/media/nxp,imx8-jpeg.yaml
> +++ b/Documentation/devicetree/bindings/media/nxp,imx8-jpeg.yaml
> @@ -32,19 +32,27 @@ properties:
>      maxItems: 1
>  
>    interrupts:
> -    description: |
> -      There are 4 slots available in the IP, which the driver may use
> -      If a certain slot is used, it should have an associated interrupt
> -      The interrupt with index i is assumed to be for slot i
> -    minItems: 1               # At least one slot is needed by the driver
> -    maxItems: 4               # The IP has 4 slots available for use
> +    description:
> +      Interrupt number for slot
> +    maxItems: 1

The device still has four interrupts, so we should allow up to four of
them. One given OS might want to use two or all four slots.


>  
>    power-domains:
>      description:
>        List of phandle and PM domain specifier as documented in
>        Documentation/devicetree/bindings/power/power_domain.txt
> -    minItems: 2               # Wrapper and 1 slot
> -    maxItems: 5               # Wrapper and 4 slots
> +    minItems: 1               # Mixed power domain
> +    maxItems: 2               # Wrapper and 1 slot
> +
> +  nxp,slot:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Integer number of slot index used. This IP includes a jpeg wrapper, the
> +      wrapper is working on descriptor based manner. It supports up to 4 slots,
> +      each slot can have its own chained descriptors. The purpose is to share
> +      the jpeg engine across multiple VMS and os. We use this property to
> +      assign a single slot. If not specified, 0 is used by default.
> +    minimum: 0
> +    maximum: 3

default: 0



Best regards,
Krzysztof