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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Date:	Wed, 8 Jul 2015 11:01:06 -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 Tue, 7 Jul 2015, Julius Werner wrote:

> > Doug, how would you feel about reworking the patch that exports
> > usb_wakeup_enabled_descendants()?  Instead of doing it that way, create
> > and export a new subroutine in hcd.c called
> > usb_hcd_wakeup_not_needed(), or something similar.
> 
> We have a use case with another host controller (Tegra, which I think
> is still in the process of being upstreamed) where we are able to
> power down PHYs (and thus reduce power consumption) per port. I think
> we should prefer the more flexible 'number of wake devices in subtree'
> interface to be able to support cases like that. (And for the simple
> case, 'if (usb_hcd_wakeup_not_needed(hcd))' and 'if
> (!usb_wakeup_enabled_descendants(hcd->self.root_hub))' look pretty
> similar anyway.)

Okay, that's a good point.

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.

Alan Stern

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