From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA96AC433E2 for ; Mon, 7 Sep 2020 15:09:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8ECC6217BA for ; Mon, 7 Sep 2020 15:09:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730124AbgIGPJl (ORCPT ); Mon, 7 Sep 2020 11:09:41 -0400 Received: from netrider.rowland.org ([192.131.102.5]:58485 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1730114AbgIGO7B (ORCPT ); Mon, 7 Sep 2020 10:59:01 -0400 Received: (qmail 763064 invoked by uid 1000); 7 Sep 2020 10:59:00 -0400 Date: Mon, 7 Sep 2020 10:59:00 -0400 From: "stern@rowland.harvard.edu" To: Hamish Martin Cc: "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" , "robh+dt@kernel.org" , "linux-usb@vger.kernel.org" , "devicetree@vger.kernel.org" Subject: Re: [PATCH 1/2] usb: ohci: Add per-port overcurrent quirk Message-ID: <20200907145900.GC762136@rowland.harvard.edu> References: <20200904032247.11345-1-hamish.martin@alliedtelesis.co.nz> <20200904032247.11345-2-hamish.martin@alliedtelesis.co.nz> <20200904154517.GB694058@rowland.harvard.edu> <9ba7b4dda9ef40e3c4c9b3f1c33075e04601ef61.camel@alliedtelesis.co.nz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9ba7b4dda9ef40e3c4c9b3f1c33075e04601ef61.camel@alliedtelesis.co.nz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 07, 2020 at 01:50:10AM +0000, Hamish Martin wrote: > Hi Alan, > > Thanks for your quick feedback. My replies are inline below. > > On Fri, 2020-09-04 at 11:45 -0400, Alan Stern wrote: > > On Fri, Sep 04, 2020 at 03:22:46PM +1200, Hamish Martin wrote: > > > Some integrated OHCI controller hubs do not expose all ports of the > > > hub > > > to pins on the SoC. In some cases the unconnected ports generate > > > spurious overcurrent events. For example the Broadcom 56060/Ranger > > > 2 SoC > > > contains a nominally 3 port hub but only the first port is wired. > > > > > > Default behaviour for ohci-platform driver is to use "ganged" > > > overcurrent protection mode. This leads to the spurious overcurrent > > > events affecting all ports in the hub. > > > > > > Allow this to be rectified by specifying per-port overcurrent > > > protection > > > mode via the device tree. > > > > > > Signed-off-by: Hamish Martin > > > --- > > > drivers/usb/host/ohci-hcd.c | 4 ++++ > > > drivers/usb/host/ohci-platform.c | 3 +++ > > > drivers/usb/host/ohci.h | 1 + > > > 3 files changed, 8 insertions(+) > > > > > > diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci- > > > hcd.c > > > index dd37e77dae00..01e3d75e29d9 100644 > > > --- a/drivers/usb/host/ohci-hcd.c > > > +++ b/drivers/usb/host/ohci-hcd.c > > > @@ -687,6 +687,10 @@ static int ohci_run (struct ohci_hcd *ohci) > > > val |= RH_A_NPS; > > > ohci_writel (ohci, val, &ohci->regs->roothub.a); > > > } > > > + if (ohci->flags & OHCI_QUIRK_PER_PORT_OC) { > > > + val |= RH_A_OCPM; > > > + ohci_writel(ohci, val, &ohci->regs->roothub.a); > > > + } > > > > I don't think this is right, for two reasons. First, isn't per-port > > overcurrent protection the default? > > Not as far as I understand the current code. Just above where my patch > applies, the RH_A_OCPM (and RH_A_PSM) bits are explicitly cleared in > 'val' with: > val &= ~(RH_A_PSM | RH_A_OCPM); > > This, coupled with the OHCI_QUIRK_HUB_POWER being set by virtue of the > 'distrust_firmware' module param defaulting true, reads to me like the > default is for ganged over-current protection. And that is my > experience in this case. You're right about that. I hadn't noticed before; it makes little sense to have a quirk that defaults to true. It's not easy to tell the full story from the kernel history; that module parameter predates the Git era. I did learn that it was modified in 2.6.3-rc3 and goes back even farther: see https://marc.info/?l=linux-usb-devel&m=110628457424684&w=2 > If none of the quirks are selected then all of the fiddling with 'val' > never gets written to 'ohci->regs->roothub.a' > > I'd appreciate your reading of that analysis because I'm by no means > sure of it. > > > > > Second, RH_A_OCPM doesn't do anything unless RH_A_NOCP is clear. > > Correct, and that is my mistake. If I progress to a v2 of this patch I > will update accordingly. Shall we try changing the parameter's default value? The USB subsystem is a lot more mature and reliable now than it was back in 2004. Alan Stern