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

Hans de Goede hdegoede at redhat.com
Thu May 8 00:29:16 PDT 2014


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?




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