[PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval

Maxime Ripard
2014-05-07T22:00:49Z

On Wed, May 07, 2014 at 10:25:55AM -0400, Alan Stern wrote:
> On Tue, 6 May 2014, Maxime Ripard wrote:
>
> > From: Boris BREZILLON <boris.brezillon@free-electrons.com>
> >
> > On the Allwinner's A31 SoC the reset line connected to the EHCI IP has to
> > be deasserted for the EHCI block to be usable.
> >
> > Add support for an optional reset controller that will be deasserted on
> > power off and asserted on power on.
> >
> > Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
> > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>
> Is this really a _reset_ line? That is, when you assert the reset
> line, does it actually reset the EHCI controller, or does it merely
> leave the controller in a partially powered-down state?

It actually resets the whole controller.

> The difference is important. During suspend, the controller is
> supposed to remember the state of the port connections as well as other
> settings. If it doesn't, the controller and all attached USB devices
> will have to be reinitialized every time the controller resumes, which
> will increase the latency.

So you're saying that we should move this to the probe then?

Thanks,
Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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