linux-kernel - Re: [RESEND PATCH 1/3] usb: dwc3: Don't reinitialize core during host bus-suspend/resume

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Date:   Thu, 11 Jan 2018 11:23:05 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Roger Quadros <rogerq@...com>, Manu Gautam <mgautam@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>
Subject: Re: [RESEND PATCH 1/3] usb: dwc3: Don't reinitialize core during host bus-suspend/resume


Hi,

Roger Quadros <rogerq@...com> writes:
>>> In host mode runtime suspend/resume could happen very often with
>>> device connected, and resetting h/w on every runtime_resume might not
>>> be desired. And PHYs drivers can also support runtime_suspend which
>>> would be preferred instead of shutting down phy.
>> 
>> We don't do anything when dwc3 is working as a host, we simply assume if
>> we reach dwc3.ko, xhci has done its part. Here's what our
>> suspend_common looks like:
>> 
>> static int dwc3_suspend_common(struct dwc3 *dwc)
>> {
>> 	unsigned long	flags;
>> 
>> 	switch (dwc->current_dr_role) {
>> 	case DWC3_GCTL_PRTCAP_DEVICE:
>> 		spin_lock_irqsave(&dwc->lock, flags);
>> 		dwc3_gadget_suspend(dwc);
>> 		spin_unlock_irqrestore(&dwc->lock, flags);
>> 		dwc3_core_exit(dwc);
>> 		break;
>> 	case DWC3_GCTL_PRTCAP_HOST:
>> 	default:
>> 		/* do nothing */
>> 		break;
>> 	}
>> 
>> 	return 0;
>> }
>> 
>> We're not resetting anything, not tearing down anything. No idea why
>> you're saying that in host mode we're breaking things apart. If you have
>> out-of-tree patches on top of v4.15-rc7, fix them instead of claiming
>> mainline is at fault.
>> 
>
> This is the case after commit 689bf72c6e0d ("usb: dwc3: Don't
> reinitialize core during host bus-suspend/resume") which is breaking
> low power for TI platforms in Host mode.
>
> If we revert that commit we will be doing dwc3_core_exit() for host
> mode as well. Which is what we want for system suspend but probably
> not for runtime suspend in host case.
>
> This is why Manu wants to differentiate runtime vs system suspend.

We already differentiate them. Maybe the only thing we need is to *not*
call core_exit() in host-mode during runtime_suspend, but call it if
mode is device or during system sleep.

-- 
balbi

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