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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 122C9C282DC for ; Sat, 6 Apr 2019 15:32:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC7952083E for ; Sat, 6 Apr 2019 15:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726600AbfDFPcc (ORCPT ); Sat, 6 Apr 2019 11:32:32 -0400 Received: from netrider.rowland.org ([192.131.102.5]:54801 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726436AbfDFPcc (ORCPT ); Sat, 6 Apr 2019 11:32:32 -0400 Received: (qmail 19478 invoked by uid 500); 6 Apr 2019 11:32:31 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 6 Apr 2019 11:32:31 -0400 Date: Sat, 6 Apr 2019 11:32:31 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Jesse Hathaway cc: Bjorn Helgaas , Ingo Molnar , Peter Zijlstra , , , Mathias Nyman , Greg Kroah-Hartman , Subject: Re: Regression causes a hang on boot with a Comtrol PCI card In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 5 Apr 2019, Jesse Hathaway wrote: > On Thu, Apr 4, 2019 at 2:14 PM Alan Stern wrote: > > Okay. You could try skipping that pci_write_config_byte() call. The > > following loop would probably time out, and you might find that the > > code crashes later on. > > > > You could also try setting try_handoff to 0 near the start of the > > routine. Your system plus the Comtrol PCI card could have the same > > sort of bug as reported in Bugzilla #77021. > > I tried both of those options and the output was similar, here is the output > with try_handoff set to 0. In both cases the box then hangs on initializing > pstore. Well, at least that's forward progress. I don't know what pstore is or what connection it has to the USB subsystem. Does the machine hang similarly if you boot without the Comtrol PCI card present? For that matter, what happens if you remove EHCI from the kernel configuration completely? > Excuse my ignorance on understanding how having the Comtrol > card present would effect the USB handoff, but would there be any > value in trying to boot this box via UEFI, rather than via the BIOS? Does > UEFI handle the handoff differently? The UEFI and the legacy BIOS are two separate pieces of code with no particular connection to one another. It's a good bet that they do pretty much everything differently. As for how the PCI card affects the USB handoff, it depends on how the BIOS behaves. Normally the BIOS will take control of all the available EHCI controllers during bootup (so that it can use them to communicate with a USB keyboard or mouse), including controllers on add-on PCI cards as well as those on the motherboard. When the kernel starts up, it tries to take ownership of the controllers away from the BIOS (that's the handoff) so that Linux can use them. However, if the BIOS was never tested for handoff of USB controllers on add-on PCI cards, it could easily have a bug that would crash the machine. Alan Stern