linux-kernel - Re: [PATCH] usb: dwc3: keep PHYs disabled during suspend

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Date:   Tue, 23 Aug 2022 11:33:18 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: keep PHYs disabled during suspend

Hi Johan,

On Tue, Aug 23, 2022 at 02:40:47PM +0200, Johan Hovold wrote:
> Commit 649f5c842ba3 ("usb: dwc3: core: Host wake up support from system
> suspend") started leaving the PHYs enabled during suspend for
> wakeup-capable controllers even though it turns out this had nothing to
> do with wakeup.
> 
> Rather, the wakeup capability flag was (ab-)used as a proxy to configure
> the suspend behaviour in an attempt to reduce power leakage on some
> platforms.
> 
> Stop abusing the wakeup configuration and restore the 5.19 behaviour of
> keeping the PHYs powered off during suspend. If needed, a dedicated
> mechanism for configuring the PHY power state during suspend can be
> added later.
> 
> Fixes: 649f5c842ba3 ("usb: dwc3: core: Host wake up support from system suspend")
> Link: https://lore.kernel.org/r/Yuv7AM/5jtO/pgcm@google.com
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/usb/dwc3/core.c      | 4 ++--
>  drivers/usb/dwc3/dwc3-qcom.c | 1 -
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 8c8e32651473..0cdb6be720e1 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1983,7 +1983,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  		dwc3_core_exit(dwc);
>  		break;
>  	case DWC3_GCTL_PRTCAP_HOST:
> -		if (!PMSG_IS_AUTO(msg) && !device_may_wakeup(dwc->dev)) {
> +		if (!PMSG_IS_AUTO(msg)) {

My assumption was that the PHYs need to be powered for wakeup to work, but
apparently that isn't the case, wakeup still works on sc7x80 with this part
of this patch.

>  			dwc3_core_exit(dwc);
>  			break;
>  		}
> @@ -2044,7 +2044,7 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  		spin_unlock_irqrestore(&dwc->lock, flags);
>  		break;
>  	case DWC3_GCTL_PRTCAP_HOST:
> -		if (!PMSG_IS_AUTO(msg) && !device_may_wakeup(dwc->dev)) {
> +		if (!PMSG_IS_AUTO(msg)) {
>  			ret = dwc3_core_init_for_resume(dwc);
>  			if (ret)
>  				return ret;
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index 9a94b1ab8f7a..9995395baa12 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -904,7 +904,6 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>  
>  	wakeup_source = of_property_read_bool(dev->of_node, "wakeup-source");
>  	device_init_wakeup(&pdev->dev, wakeup_source);
> -	device_init_wakeup(&qcom->dwc3->dev, wakeup_source);

Surprisingly this part breaks wakeup on sc7x80, with the above removal
of the device_may_wakeup() checks it is not clear to me why wakeup needs
to be enabled for the core.