linux-kernel - Re: [REPOST PATCH 3/3] USB: dwc2: Don't turn off the usbphy in suspend if wakeup is enabled

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Message-ID: <Pine.LNX.4.44L0.1507081555570.2243-100000@iolanthe.rowland.org>
Date:	Wed, 8 Jul 2015 15:58:14 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Julius Werner <jwerner@...omium.org>
cc:	Felipe Balbi <balbi@...com>,
	Douglas Anderson <dianders@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Youn <johnyoun@...opsys.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Chris Zhong <zyw@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Andrew Bresticker <abrestic@...omium.org>,
	Alexandru Stan <amstan@...omium.org>, lyz <lyz@...k-chips.com>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [REPOST PATCH 3/3] USB: dwc2: Don't turn off the usbphy in
 suspend if wakeup is enabled

On Wed, 8 Jul 2015, Julius Werner wrote:

> > But I don't see how you will make it work when the root hub itself is
> > not enabled for wakeup and a non-hub device plugged into one of the
> > root hub's ports is enabled.
> >
> > It seems like you would need a usb_hcd_wakeup_not_needed(hcd, port)
> > subroutine.
> 
> We'd just put that in the Tegra platform driver, I guess. Iterate over
> all ports, call usb_wakeup_enabled_descendants() on the connected
> device (if any) and disable that port's PHY if it returns 0 or wasn't
> connected. Since usb_wakeup_enabled_descendants() also counts
> do_remote_wakeup from the device itself and is safe to call even on
> non-hubs, that should work for all cases.

All right, that seems reasonable.  But remember not to do this if 
wakeup is enabled on the root hub -- in that case all the PHYs must 
remain powered because unplugging and plugging are both wakeup events.

Alan Stern

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