From: Doug Anderson <dianders@chromium.org>
To: Felipe Balbi <balbi@ti.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
John Youn <johnyoun@synopsys.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
Chris Zhong <zyw@rock-chips.com>,
Heiko Stuebner <heiko@sntech.de>,
Julius Werner <jwerner@chromium.org>,
Andrew Bresticker <abrestic@chromium.org>,
Alexandru Stan <amstan@chromium.org>, lyz <lyz@rock-chips.com>,
"open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [REPOST PATCH 3/3] USB: dwc2: Don't turn off the usbphy in suspend if wakeup is enabled
Date: Mon, 6 Jul 2015 12:39:27 -0700 [thread overview]
Message-ID: <CAD=FV=V1oOdYLZyw3RpdYUQMCKnhcZ=AymnTDzy6Zm=MXqnehQ@mail.gmail.com> (raw)
In-Reply-To: <20150706190212.GN20779@saruman.tx.rr.com>
Hi,
On Mon, Jul 6, 2015 at 12:02 PM, Felipe Balbi <balbi@ti.com> wrote:
> On Mon, Jul 06, 2015 at 02:58:16PM -0400, Alan Stern wrote:
>> On Mon, 6 Jul 2015, Douglas Anderson wrote:
>>
>> > If the 'snps,need-phy-for-wake' is set in the device tree then:
>> >
>> > - We know that we can wakeup, so call device_set_wakeup_capable().
>> > The USB core will use this knowledge to enable wakeup by default.
>> > - We know that we should keep the PHY on during suspend if something
>> > on our root hub needs remote wakeup. This requires the patch (USB:
>> > Export usb_wakeup_enabled_descendants()). Note that we don't keep
>> > the PHY on at suspend time if it's not needed because it would be a
>> > power draw.
>>
>> You know, this is the first time I've run across this optimization.
>>
>> In principle it applies to any USB host controller, not just to PHYs.
>> There's no reason to enable wakeup for a controller if none of the
>> attached devices can issue a wakeup request.
>>
>> I don't know if implementing this in other HCDs would save any power.
>> Any ideas?
>
> most likely it would. Enabling wakeup usually boils down to keeping a
> tiny part of the controller (or PHY) powered up. Sometimes that lies in
> an always-on power domain, so there would be no difference.
As per Andrew Bresticker (CCed on this email), the optimization made
sense in Tegra. If you're willing to look into the chromeos-3.10
tree, you can see that Andrew added a usb_port_may_wakeup() call in
<https://chromium-review.googlesource.com/196593>. He then used it in
the tegra XHCI driver in
<https://chromium-review.googlesource.com/196594>. Recently I talked
to Andrew and he indicated that rather than add usb_port_may_wakeup()
like he did it probably made sense to just export
usb_wakeup_enabled_descendants().
-Doug
next prev parent reply other threads:[~2015-07-06 19:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-06 18:27 [REPOST PATCH 0/3] dwc2 patches to allow wakeup on Rockchip rk3288 Douglas Anderson
2015-07-06 18:27 ` [REPOST PATCH 1/3] USB: Export usb_wakeup_enabled_descendants() Douglas Anderson
2015-07-06 18:27 ` [REPOST PATCH 2/3] Documentation: dt-bindings: Add snps,need-phy-for-wake for dwc2 USB Douglas Anderson
2015-07-06 18:27 ` [REPOST PATCH 3/3] USB: dwc2: Don't turn off the usbphy in suspend if wakeup is enabled Douglas Anderson
2015-07-06 18:34 ` Felipe Balbi
2015-07-06 19:32 ` Doug Anderson
2015-07-06 19:35 ` Felipe Balbi
2015-07-06 18:58 ` Alan Stern
2015-07-06 19:02 ` Felipe Balbi
2015-07-06 19:39 ` Doug Anderson [this message]
2015-07-07 14:28 ` Alan Stern
2015-07-08 0:06 ` Julius Werner
2015-07-08 15:01 ` Alan Stern
2015-07-08 19:41 ` Julius Werner
2015-07-08 19:58 ` Alan Stern
2015-10-21 16:23 ` [REPOST PATCH 0/3] dwc2 patches to allow wakeup on Rockchip rk3288 Doug Anderson
2015-10-27 2:05 ` John Youn
2015-10-31 0:01 ` Doug Anderson
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