[PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval
stern at rowland.harvard.edu
Thu May 8 07:07:25 PDT 2014
On Thu, 8 May 2014, Hans de Goede wrote:
> On 05/08/2014 12:00 AM, Maxime Ripard wrote:
> > 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 at 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 at free-electrons.com>
> >>> Signed-off-by: Maxime Ripard <maxime.ripard at 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?
That's right. The controller should not be reset during suspend, if
you can possibly avoid it.
There isn't any real benefit to asserting the reset signal during
suspend, is there? I mean, it won't use any less power, right?
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