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

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Message-ID: <58de97ff-2f16-40d4-a95c-d751fe26659c@quicinc.com>
Date: Mon, 10 Feb 2025 13:46:06 +0530
From: AKASH KUMAR <quic_akakum@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.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

Hi,

On 2/6/2025 11:19 PM, Konrad Dybcio wrote:
> 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.
Sure.
>
>> 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
Ok.
>> 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.

Will update in V2.

Thanks

Akash