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

From: [email-masked] (Maxime Ripard)
Date: Wed, 7 May 2014 17:00:49 -0500

On Wed, May 07, 2014 at 10:25:55AM -0400, Alan Stern wrote:
> On Tue, 6 May 2014, Maxime Ripard wrote:
> 
> > From: Boris BREZILLON <[email-masked]>
> > 
> > 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 <[email-masked]>
> > Signed-off-by: Maxime Ripard <[email-masked]>
> 
> 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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