linux-kernel - Re: [RFC 4/8] clk: qcom: gcc-sm8450: Keep usb30 prim gdsc on during runtime suspend

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Date:   Thu, 19 Oct 2023 14:07:20 +0530
From:   Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To:     Stephen Boyd <sboyd@...nel.org>, Andy Gross <agross@...nel.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Michael Turquette <mturquette@...libre.com>
CC:     <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <quic_ppratap@...cinc.com>,
        <quic_jackp@...cinc.com>,
        Udipto Goswami <quic_ugoswami@...cinc.com>
Subject: Re: [RFC 4/8] clk: qcom: gcc-sm8450: Keep usb30 prim gdsc on during
 runtime suspend



On 10/19/2023 6:28 AM, Stephen Boyd wrote:
> Quoting Krishna Kurapati (2023-10-17 06:19:44)
>> When runtime suspend happens in host mode, if cable is removed at this
>> instant, it triggers a resume where a xhci register access is done when
>> gdsc is not on leading to a crash. Keep usb30 prim gdsc as on during
>> runtime suspend to avoid this crash.
>>
>> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
>> ---
>> Note: I am not sure if this is the right way or setting GDSC flags to
>> PWRSTS_RET_ON is the right approach. So for now made this change to
> 
> Does using PWRSTS_RET_ON work? Does the GDSC support being turned off or
> is the lowest power state retention?

I didn't see any issue when I put it as PWRSTS_RET_ON. If the GDSC is 
off, when we remove cable in host mode, we see a crash because of xhci 
register access. But when I try putting PWRSTS_RET_ON / 
CLK_RPM_ALWAYS_ON it doesn't crash.

Regard,
Krishna,