linux-kernel - Re: [PATCH v2 08/19] arm64: dts: qcom: Disable USB U1/U2 entry for SA8775P

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Message-ID: <1fd62c05-36fe-4059-9277-0946e1e3a933@quicinc.com>
Date: Sat, 14 Dec 2024 11:01:26 +0530
From: Prashanth K <quic_prashk@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        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>,
        Krishna Kurapati <krishna.kurapati@....qualcomm.com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <cros-qcom-dts-watchers@...omium.org>
Subject: Re: [PATCH v2 08/19] arm64: dts: qcom: Disable USB U1/U2 entry for
 SA8775P



On 14-12-24 05:36 am, Konrad Dybcio wrote:
> On 13.12.2024 10:52 AM, Prashanth K wrote:
>> From: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
>>
>> Disable U1 and U2 power-saving states to improve stability of USB.
>> These low-power link states, designed to reduce power consumption
>> during idle periods, can cause issues in latency-sensitive or high
>> throughput use cases. Over the years, some of the issues seen are
>> as follows:
>>
>> 1. In device mode of operation, when UVC is active, enabling U1/U2
>> is sometimes causing packets drops due to delay in entry/exit of
>> intermittent these low power states. These packet drops are often
>> reflected as missed isochronous transfers, as the controller wasn't
>> able to send packet in that microframe interval and hence glitches
>> are seen on the final transmitted video output.
>>
>> 2. On QCS6490-Rb3Gen2 Vision kit, ADB connection is heavily unstable
>> when U1/U2 is enabled. Often when link enters U2, there is a re-
>> enumeration seen and device is unusable for many use cases.
>>
>> 3. On QCS8300/QCS9100, it is observed that when Link enters U2, when
>> the cable is disconnected and reconnected to host PC in HS, there
>> is no link status change interrupt seen and the plug-in in HS doesn't
>> show up a bus reset and enumeration failure happens.
>>
>> Disabling these intermittent power states enhances device stability
>> without affecting power usage.
>>
>> Signed-off-by: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
>> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
>> ---
> 
> [...]
> 
>>  
>> @@ -3570,6 +3576,8 @@ tcsr_mutex: hwlock@...0000 {
>>  			compatible = "qcom,tcsr-mutex";
>>  			reg = <0x0 0x01f40000 0x0 0x20000>;
>>  			#hwlock-cells = <1>;
>> +				snps,dis-u1-entry-quirk;
>> +				snps,dis-u2-entry-quirk;
> 
> Oh?
> 
Thanks for pointing. I messed up, will update and send next version.

Regards,
Prashanth K