linux-kernel - Re: [PATCH 4/6] usb: cdns3: support power-off of controller when in host role

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Date:   Fri, 17 Nov 2023 11:38:14 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Théo Lebrun <theo.lebrun@...tlin.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Roger Quadros <rogerq@...nel.org>,
        Pawel Laszczak <pawell@...ence.com>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/6] usb: cdns3: support power-off of controller when in
 host role

On 23-11-14 12:10:18, Théo Lebrun wrote:
> Hello,
> 
> On Tue Nov 14, 2023 at 9:38 AM CET, Peter Chen wrote:
> > On 23-11-13 15:26:59, Théo Lebrun wrote:
> > > The controller is not being reconfigured at resume. Change resume to
> > > redo hardware config if quirk CDNS3_RESET_ON_RESUME is active.
> >
> > Current logic has power off judgement, see cdns3_controller_resume for
> > detail.
> 
> Indeed! Thanks for the pointer. I had not noticed that, those patches
> come from an older kernel which didn't have it. That'll make for less
> changes; patches 4 & 5 can go away.
> 
> > > +	if (cdns->pdata && cdns->pdata->quirks & CDNS3_RESET_ON_RESUME)
> > > +		cdns->xhci_plat_data->quirks |= XHCI_RESET_ON_RESUME | XHCI_SUSPEND_RESUME_CLKS;
> > > +
> >
> > If you set this flag, how could you support the USB remote wakeup
> > request? In that case, the USB bus does not expect re-enumeration.
> 
> We didn't support remote USB wakeup. Only S2R mattered in our case and
> USB remote wakeup wasn't a possibility.

Without this patch, will below be hit for your platform:


	/* re-initialize the HC on Restore Error, or Host Controller Error */
	if (temp & (STS_SRE | STS_HCE)) {
		reinit_xhc = true;
		if (!xhci->broken_suspend)
			xhci_warn(xhci, "xHC error in resume, USBSTS 0x%x, Reinit\n", temp);
	}


-- 

Thanks,
Peter Chen