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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A0BFBC433E2 for ; Tue, 16 Jun 2020 12:31:51 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 72F5520734 for ; Tue, 16 Jun 2020 12:31:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72F5520734 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jlAkZ-0002eU-JJ; Tue, 16 Jun 2020 12:31:35 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jlAkY-0002eP-Ig for xen-devel@lists.xenproject.org; Tue, 16 Jun 2020 12:31:34 +0000 X-Inumbo-ID: 4f68b114-afcd-11ea-bb8b-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4f68b114-afcd-11ea-bb8b-bc764e2007e4; Tue, 16 Jun 2020 12:31:32 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 752CBAD35; Tue, 16 Jun 2020 12:31:35 +0000 (UTC) Subject: Re: [PATCH 1/1] x86/acpi: Use FADT flags to determine the PMTMR width To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <6b921b43-03f6-448c-297e-8c8f041eea2a@suse.com> <20200616103204.GN735@Air-de-Roger> From: Jan Beulich Message-ID: <440b1c62-e3bd-6a91-f75f-e85d8772f4e0@suse.com> Date: Tue, 16 Jun 2020 14:31:30 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200616103204.GN735@Air-de-Roger> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: artur@puzio.waw.pl, Wei Liu , jakub@bartmin.ski, Andrew Cooper , marmarek@invisiblethingslab.com, Grzegorz Uriasz , j.nowak26@student.uw.edu.pl, xen-devel@lists.xenproject.org Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 16.06.2020 12:32, Roger Pau Monné wrote: > On Tue, Jun 16, 2020 at 10:07:05AM +0200, Jan Beulich wrote: >> On 14.06.2020 16:36, Grzegorz Uriasz wrote: >>> --- a/xen/arch/x86/acpi/boot.c >>> +++ b/xen/arch/x86/acpi/boot.c >>> @@ -480,7 +480,10 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table) >>> if (fadt->xpm_timer_block.space_id == >>> ACPI_ADR_SPACE_SYSTEM_IO) { >>> pmtmr_ioport = fadt->xpm_timer_block.address; >>> - pmtmr_width = fadt->xpm_timer_block.bit_width; >>> + if (fadt->flags & ACPI_FADT_32BIT_TIMER) >>> + pmtmr_width = 32; >>> + else >>> + pmtmr_width = 24; >> >> I think disagreement of the two wants logging, and you want to >> default to using the smaller of the two (or even to ignoring the >> timer altogether). Then there wants to be a way to override >> (unless we already have one) our defaulting, in case it's wrong. > > TBH, I presume timer_block will always return 32bits, because that's > the size of the register. Then the timer can implement less bits than > the full size of the register, and that's what gets signaled using the > ACPI flags. What we care about here is the number of bits used by the > timer, not the size of the register. The first random system I checked this on reports 24 bits as bit_width (and the flag clear, i.e. both are consistent). The flag, aiui, is really important only in the ACPI v1 case, where the size of the register was a byte-granular value. The spec isn't helpful in clarifying applicability of the flag though, i.e. one can interpret it either way imo. Jan > I think we should only ignore the timer if pm_timer_block.bit_width < > pmtmr_width. > > Printing a (debug) message when those values disagree is fine, but I > bet it's going to trigger always when the implemented timer is only > using 24bits. > > Roger. >