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: <CAODwPW-O8g+X8wiPH=m8q+BR1-V36dcgykM12DofiXZMU=9_3A@mail.gmail.com>
Date:	Tue, 7 Jul 2015 17:06:29 -0700
From:	Julius Werner <jwerner@...omium.org>
To:	Alan Stern <stern@...land.harvard.edu>
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>,
	Julius Werner <jwerner@...omium.org>,
	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

> 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.)
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