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Message-ID: <d50abf1a-1ee7-4f84-9f53-69dfe9aad103@linaro.org>
Date: Fri, 15 Dec 2023 08:36:45 +0100
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Subject: Re: [PATCH v2 1/3] dt-bindings: usb: mtk-xhci: add a property for
 Gen1 isoc-in transfer issue
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To: Chunfeng Yun <chunfeng.yun@mediatek.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Conor Dooley <conor+dt@kernel.org>,
 Matthias Brugger <matthias.bgg@gmail.com>,
 Mathias Nyman <mathias.nyman@intel.com>, linux-usb@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org,
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
 Macpaul Lin <macpaul.lin@mediatek.com>, Eddie Hung <eddie.hung@mediatek.com>
References: <20231215073431.8512-1-chunfeng.yun@mediatek.com>
From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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In-Reply-To: <20231215073431.8512-1-chunfeng.yun@mediatek.com>
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On 15/12/2023 08:34, 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 2;
> The side-effect is that may cause performance drop about 10%, including
> bulk transfer.
> 
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> ---
> 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..e44a71acb5c0 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 2 here.

What is the meaning of 0-3? bytes? words?

> +    minimum: 0
> +    maximum: 3


Best regards,
Krzysztof