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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 4C184CA90AF for ; Tue, 12 May 2020 19:35:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29A0A20731 for ; Tue, 12 May 2020 19:35:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FCRJx0YG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731004AbgELTf3 (ORCPT ); Tue, 12 May 2020 15:35:29 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:43532 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730950AbgELTf2 (ORCPT ); Tue, 12 May 2020 15:35:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589312127; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=H5pxUSbLWxNQVZt3chJU6aQ+MxFijTrdJFOgatW5PJM=; b=FCRJx0YGfOyJFnV8FqbaYpk2jVd6iwrDVN3dyPl3LIPwYfOWZ7b4Ml9Ai/Oc1OThRoEzKC 51GeuI7p1PJNI4U3tvz5F2Ylhm89ybQvDxEbGhxgcjgzDcwNveUxGSwqaCQOk/4tRhWtw7 mMDKEdiX5wd8g4zEHoVma0cVms5nFnU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-189-Cs80k05zNKOHzuw-ckzSlg-1; Tue, 12 May 2020 15:35:25 -0400 X-MC-Unique: Cs80k05zNKOHzuw-ckzSlg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C474F100A623; Tue, 12 May 2020 19:35:23 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (file01.intranet.prod.int.rdu2.redhat.com [10.11.5.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3394839D; Tue, 12 May 2020 19:35:22 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (localhost [127.0.0.1]) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4) with ESMTP id 04CJZMnE032376; Tue, 12 May 2020 15:35:22 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 04CJZLMo032373; Tue, 12 May 2020 15:35:21 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Tue, 12 May 2020 15:35:21 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: "Maciej W. Rozycki" cc: Arnd Bergmann , Richard Henderson , Ivan Kokshaysky , Matt Turner , Greg Kroah-Hartman , alpha , linux-serial@vger.kernel.org, linux-rtc@vger.kernel.org Subject: Re: [PATCH 1/2 v3] alpha: add a delay to inb_p, inb_w and inb_l In-Reply-To: Message-ID: References: User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-rtc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rtc@vger.kernel.org On Mon, 11 May 2020, Maciej W. Rozycki wrote: > And if timing is indeed the culprit, then I think it will be best fixed > in the 82378IB southbridge, i.e.[1]: > > "The I/O recovery mechanism in the SIO is used to add additional recovery > delay between PCI originated 8-bit and 16-bit I/O cycles to the ISA Bus. > The SIO automatically forces a minimum delay of four SYSCLKs between > back-to-back 8 and 16 bit I/O cycles to the ISA Bus. The delay is > measured from the rising edge of the I/O command (IOR# or IOW#) to the > falling edge of the next BALE. If a delay of greater than four SYSCLKs is > required, the ISA I/O Recovery Time Register can be programmed to increase > the delay in increments of SYSCLKs. Note that no additional delay is > inserted for back-to-back I/O "sub cycles" generated as a result of byte > assembly or disassembly. This register defaults to 8 and 16-bit recovery > enabled with two clocks added to the standard I/O recovery." > > where it won't be causing unnecessary overhead for native PCI devices or > indeed excessive one for ISA devices. It might be interesting to note > that later SIO versions like the 82378ZB increased the minimum to five > SYSCLKs, so maybe a missing SYSCLK (that can still be inserted by suitably > programming the ICRT) is the source of the problem? > > References: > > [1] "82378IB System I/O (SIO)", April 1993, Intel Corporation, Order > Number: 290473-002, Section 4.1.17 "ICRT -- ISA Controller Recovery > Timer Register" > > Maciej I tried to modify this register (I wrote 0x44 to it - it should correspond to the maximum delay) and it had no effect on the serial port and rtc lock-ups. Mikulas