linux-kernel - Re: [PATCH] usb: chipidea: host: Disable port power only if previously enabled

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Date:   Sun, 29 Dec 2019 11:40:52 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Guenter Roeck <linux@...ck-us.net>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        Kernel development list <linux-kernel@...r.kernel.org>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: chipidea: host: Disable port power only if previously
 enabled

On Sun, 29 Dec 2019, Guenter Roeck wrote:

> On Sat, Dec 28, 2019 at 02:33:01PM -0500, Alan Stern wrote:
> > 
> > Let's try a slightly different approach.  What happens with this patch?
> > 
> > Alan Stern
> > 
> > 
> > Index: usb-devel/drivers/usb/core/hub.c
> > ===================================================================
> > --- usb-devel.orig/drivers/usb/core/hub.c
> > +++ usb-devel/drivers/usb/core/hub.c
> > @@ -1065,6 +1065,7 @@ static void hub_activate(struct usb_hub
> >  		if (type == HUB_INIT) {
> >  			delay = hub_power_on_good_delay(hub);
> >  
> > +			hub->power_bits[0] = ~0UL;	/* All ports on */
> >  			hub_power_on(hub, false);
> >  			INIT_DELAYED_WORK(&hub->init_work, hub_init_func2);
> >  			queue_delayed_work(system_power_efficient_wq,
> > 
> 
> That doesn't make a difference - the traceback is still seen with this patch
> applied.

Can you trace what's going on?  Does this code pathway now end up
calling ehci_port_power() for each root-hub port, and from there down
into the chipidea driver?  If not, can you find where it gets
sidetracked?

Alan Stern