linux-kernel - Re: [PATCH 00/18] Reserve high bandwidth for HS isoc eps

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Message-ID: <4646aec4-0270-435e-8097-344a1df0e4bc@kernel.org>
Date: Mon, 10 Feb 2025 09:22:23 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Akash Kumar <quic_akakum@...cinc.com>,
 Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jack Pham <quic_jackp@...cinc.com>, kernel@....qualcomm.com,
 Wesley Cheng <quic_wcheng@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Vijayavardhan Vennapusa <quic_vvreddy@...cinc.com>,
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/18] Reserve high bandwidth for HS isoc eps

On 06/02/2025 12:15, Akash Kumar wrote:
> It is observed while testing multiple audio devices over usb, a glitch is
> observed during testing. As per dwc datasheet,By default, HC reserves 80%
> of the bandwidth for periodic EPs which can be increased if needed.
> 
> Add quirk to set GUCTL register BIT 16 to accommodate higher bandwidth for
> 2 isoc eps.
> 
> If this bit is set, the bandwidth is relaxed to 85% to accommodate two high
> speed, high bandwidth ISOC EPs. USB 2.0 required 80% bandwidth allocated
> for ISOC traffic. If two High-bandwidth ISOC devices (HD Webcams) are
> connected, and if each requires 1024-bytes X 3 packets per Micro-Frame,
> then the bandwidth required is around 82%. If this bit is set, then it is
> possible to connect two Webcams of 1024bytes X 3 paylod per Micro-Frame
> each. Alternatively, you might need to lower the resolution of the
> webcams. This bit is valid in Host and DRD configuration and is used in
> host mode operation only.
> 
> Set this bit for host mode uvc uac usecases where two isoc eps are used
> and uvc flickers or audio glitch is observed.
> 
> Akash Kumar (18):
>   usb: dwc3: Reserve Higher Bandwidth for HS Periodic EPs
>   arm64: dts: qcom: sa8775p: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm8350: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm8450: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm8150: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm6125: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm8250: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sm6350: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sc7280: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sdm630: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sdm845: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sdx75: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: qcs404: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sc7180: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: x1e80100: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sc8280xp: Enable high bandwidth for hs isoc eps
>   arm64: dts: qcom: sc8180x: Enable high bandwidth for hs isoc eps

1. Do not combine USB and DTS in one patchset.
2. This was not ever tested (see bug reports already published by bot),
so obviously disappointing no-go.
3. This looks like SoC specific, so deduce the setting from the compatible.


Best regards,
Krzysztof