linux-kernel - Re: [PATCH v4 1/3] dt-bindings: usb: mtk-xhci: add a property for Gen1 isoc-in transfer issue

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Date: Thu, 4 Jan 2024 06:12:26 +0000
From: Chunfeng Yun (云春峰) <Chunfeng.Yun@...iatek.com>
To: "mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"mathias.nyman@...el.com" <mathias.nyman@...el.com>,
	Eddie Hung (洪正鑫) <Eddie.Hung@...iatek.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	Macpaul Lin (林智斌) <Macpaul.Lin@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>
Subject: Re: [PATCH v4 1/3] dt-bindings: usb: mtk-xhci: add a property for
 Gen1 isoc-in transfer issue

On Thu, 2023-12-28 at 12:44 +0200, Mathias Nyman wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Hi
> 
> On 27.12.2023 8.03, 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.
> 
> Is it be possible to detect those Mediatek xHC versions that need
> this
> workaround in the xhci-mtk driver directly?
the version info is saved in IPPC register, when support dual-role
mode, xhci-mtk driver can't access these register which are controlled
by dual-role controller mtu3 driver;
another reason is that some cases, e.g. connected a on-board fixed mass
storage device, do not use 4K camera, it's better to use the default
rx-fifo-depth;

Thanks
> 
> This way we could avoid passing a new "rx-fifo-depth" property to it.
> 
> Thanks
> Mathias
> 
>