linux-kernel - Re: [PATCH 01/18] usb: dwc3: Reserve Higher Bandwidth for HS Periodic EPs

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Message-ID: <d0b86591-7bac-42a0-aeac-1f7f6b75b75e@oss.qualcomm.com>
Date: Thu, 6 Feb 2025 18:49:14 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
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 01/18] usb: dwc3: Reserve Higher Bandwidth for HS Periodic
 EPs

On 6.02.2025 12:15 PM, Akash Kumar wrote:
> On targets using synopsys usb dwc3 controller, it is observed while testing
> multiple audio devices, 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 with GUCTL Bit 16.

It is observed a glitch is observed.. please massage this paragraph
a bit.

> 
> 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 flicker is seen.

Re-format your commit text to wrap at ~72 characters
> 
> Signed-off-by: Akash Kumar <quic_akakum@...cinc.com>
> ---
>  drivers/usb/dwc3/core.c | 11 +++++++++++
>  drivers/usb/dwc3/core.h |  4 ++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index dfa1b5fe48dc..7e55c234e4e5 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1461,6 +1461,14 @@ static int dwc3_core_init(struct dwc3 *dwc)
>  		dwc3_writel(dwc->regs, DWC3_GUCTL1, reg);
>  	}
>  
> +	if (dwc->revision >= DWC3_REVISION_250A) {
> +		if (dwc->dwc3_guctl_resbwhseps_quirk) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GUCTL);
> +			reg |= DWC3_GUCTL_RESBWHSEPS;
> +			dwc3_writel(dwc->regs, DWC3_GUCTL, reg);
> +		}
> +	}
> +
>  	dwc3_config_threshold(dwc);
>  
>  	/*
> @@ -1818,6 +1826,9 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  	dwc->dis_split_quirk = device_property_read_bool(dev,
>  				"snps,dis-split-quirk");
>  
> +	dwc->dwc3_guctl_resbwhseps_quirk = device_property_read_bool(dev,
> +				"snps,dwc3_guctl_resbwhseps_quirk");

This needs a dt-bindings entry. Also, underscores are forbidden in property
names, use hyphens instead.

Konrad