From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932069AbcF2WRl (ORCPT ); Wed, 29 Jun 2016 18:17:41 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:52662 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751932AbcF2WRd (ORCPT ); Wed, 29 Jun 2016 18:17:33 -0400 Subject: Re: [PATCH V2 1/4] ACPI,PCI,IRQ: factor in PCI possible To: "Rafael J. Wysocki" References: <1467188859-28188-1-git-send-email-okaya@codeaurora.org> <1467188859-28188-2-git-send-email-okaya@codeaurora.org> <8a40e242-fca4-5681-e480-e29ec05354ac@codeaurora.org> Cc: ACPI Devel Maling List , Timur Tabi , Christopher Covington , Jon Masters , Alex Williamson , eric.auger@redhat.com, Linux PCI , Andy Gross , linux-arm-msm@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" , wim@djo.tudelft.nl, perex@perex.cz, tiwai@suse.com, "Rafael J. Wysocki" , Len Brown , Linux Kernel Mailing List From: Sinan Kaya Message-ID: <280859fd-07a0-9cea-c9d4-f956241e8986@codeaurora.org> Date: Wed, 29 Jun 2016 17:21:27 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/29/2016 5:19 PM, Rafael J. Wysocki wrote: > On Wed, Jun 29, 2016 at 8:47 PM, Sinan Kaya wrote: >> On 6/29/2016 9:13 AM, Rafael J. Wysocki wrote: >>> On Wed, Jun 29, 2016 at 10:27 AM, Sinan Kaya wrote: >>>> The change introduced in commit 103544d86976 ("ACPI,PCI,IRQ: reduce >>>> resource requirements") omitted the initially assigned POSSIBLE penalty >>>> when the IRQ is active. >>> >>> It would be good to say what can go wrong with that here. >>> >> >> I can add more description. Here is a first attempt. >> >> Incorrect calculation of penalty leads to ACPI code assigning the wrong >> interrupt number to PCI INTx interrupts. >> >> This would not be as bad as it sounds in theory. You would just cause the >> interrupts to be shared and observe performance penalty. >> >> However, some drivers like parallel port driver doesn't like interrupt >> sharing as in this example and causes all other PCI drivers sharing the interrupt >> to malfunction. >> >> The issue has not been caught because the behavior is platform specific >> and depends on the peripheral drivers sharing the IRQ. >> >> I can claim that this could be a BIOS bug. if interrupt 7 is not good for PCI, >> it shouldn't have been listed in the possible PCI interrupts to begin with. >> Given this is an existing platform, I don't think we have the luxury to request >> all BIOS to be updated. This bugfix is needed to support existing platforms. >> >> >> Feel free to request more information if the above description is not clear. > > It is clear enough. I can add it to the changelog when applying the patch. OK > >> >>>> The original code would assign the POSSIBLE value divided by the number >>>> of possible IRQs during initialization. >>>> >>>> Later, if the IRQ is chosen as the active IRQ or if the IRQ is in use >>>> by ISA; additional penalties get added. > > Does "later" here mean "later in that code path" or "in a later patch"? "later in that code path" > > Thanks, > Rafael > -- Sinan Kaya Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project