From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933263AbaEGOZ7 (ORCPT ); Wed, 7 May 2014 10:25:59 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:42511 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932989AbaEGOZ4 (ORCPT ); Wed, 7 May 2014 10:25:56 -0400 Date: Wed, 7 May 2014 10:25:55 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Maxime Ripard cc: Emilio Lopez , Mike Turquette , , , Boris Brezillon , , , , , , , , , Boris BREZILLON Subject: Re: [PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval In-Reply-To: <1399434623-20383-5-git-send-email-maxime.ripard@free-electrons.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 6 May 2014, Maxime Ripard wrote: > From: Boris BREZILLON > > 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 > Signed-off-by: Maxime Ripard 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? 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. Alan Stern From mboxrd@z Thu Jan 1 00:00:00 1970 From: stern@rowland.harvard.edu (Alan Stern) Date: Wed, 7 May 2014 10:25:55 -0400 (EDT) Subject: [PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval In-Reply-To: <1399434623-20383-5-git-send-email-maxime.ripard@free-electrons.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 6 May 2014, Maxime Ripard wrote: > From: Boris BREZILLON > > 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 > Signed-off-by: Maxime Ripard 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? 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. Alan Stern