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Subject: Re: [PATCH v4 1/3] dt-bindings: usb: mtk-xhci: add a property for
 Gen1 isoc-in transfer issue
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>, Eddie Hung <eddie.hung@mediatek.com>, Macpaul
 Lin <macpaul.lin@mediatek.com>
References: <20231227060316.8539-1-chunfeng.yun@mediatek.com>
From: Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <1e5772b3-2e71-069c-5794-ded2ee72222f@omp.ru>
Date: Wed, 27 Dec 2023 12:19:42 +0300
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On 12/27/23 9:03 AM, 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

   That it may cause?

> bulk transfer.
> 
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> ---
> v4: change rx-fifo size in bytes
> 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    | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> index e9644e333d78..9f621f2209df 100644
> --- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> +++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
> @@ -124,6 +124,17 @@ 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

   Finishes.

> +      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,

   That it may cause? And including?

[...]

MBR, Sergey