linux-kernel - Re: [PATCH v3 1/3] dt-bindings: usb: mtk-xhci: add a property for Gen1 isoc-in transfer issue

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Message-ID: <c3d372f0-3d21-4500-96cd-9c88aaf5ce89@linaro.org>
Date: Wed, 20 Dec 2023 08:38:07 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Chunfeng Yun <chunfeng.yun@...iatek.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Conor Dooley <conor+dt@...nel.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Mathias Nyman <mathias.nyman@...el.com>, linux-usb@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Eddie Hung <eddie.hung@...iatek.com>, Macpaul Lin <macpaul.lin@...iatek.com>
Subject: Re: [PATCH v3 1/3] dt-bindings: usb: mtk-xhci: add a property for
 Gen1 isoc-in transfer issue

On 20/12/2023 03:58, Chunfeng Yun wrote:
> For Gen1 isoc-in endpoint on controller before about SSUSB IPM v1.6.0, it
> still send out unexpected ACK after receiving a short packet in burst
> transfer, this will cause an exception on connected device, specially for
> a 4k camera.
> Add a quirk property "rx-fifo-depth" to work around this hardware issue,
> prefer to use 3k bytes;
> The side-effect is that may cause performance drop about 10%, including
> bulk transfer.
> 
> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> ---
> v3: add fifo depth unit, change the value range from 0-3 to 1-4
> v2: change 'mediatek,rxfifo-depth' to 'rx-fifo-depth'
> ---
>  .../devicetree/bindings/usb/mediatek,mtk-xhci.yaml   | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> index e9644e333d78..9478b7031796 100644
> --- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> +++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> @@ -124,6 +124,18 @@ properties:
>        defined in the xHCI spec on MTK's controller.
>      default: 5000
>  
> +  rx-fifo-depth:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      It is a quirk used to work around Gen1 isoc-in endpoint transfer issue
> +      that still send out unexpected ACK after device finish the burst transfer
> +      with a short packet and cause an exception, specially on a 4K camera
> +      device, it happens on controller before about IPM v1.6.0; the side-effect
> +      is that may cause performance drop about 10%, include bulk transfer,
> +      prefer to use 3 here. The unit is 1K bytes.

NAK. Read comments on previous submission.

Best regards,
Krzysztof