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

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Date:   Thu, 26 Dec 2019 14:46:15 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Guenter Roeck <linux@...ck-us.net>
cc:     Peter Chen <peter.chen@...escale.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <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 Thu, 26 Dec 2019, Guenter Roeck wrote:

> On shutdown, ehci_power_off() is called unconditionally to power off
> each port, even if it was never called to power on the port.
> For chipidea, this results in a call to ehci_ci_portpower() with a request
> to power off ports even if the port was never powered on.
> This results in the following warning from the regulator code.

That's weird -- we should always power-on every port during hub 
initialization.

It looks like there's a bug in hub.c:hub_activate(): The line under
HUB_INIT which calls hub_power_on() should call
usb_hub_set_port_power() instead.  In fact, the comment near the start
of hub_power_on() is wrong.  It says "Enable power on each port", but
in fact it only enables power for ports that had been powered-on
previously (i.e., the port's bit in hub->power_bits was set).  
Apparently this got messed up in commit ad493e5e5805 ("usb: add usb
port auto power off mechanism").

Now, the chipidea driver may still need to be updated, because 
ehci_turn_off_all_ports() will still be called during shutdown and it 
will try to power-down all ports, even those which are already powered 
down (for example, because the port is suspended).

Alan Stern