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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 F115CC28CBC for ; Wed, 6 May 2020 11:23:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD38420663 for ; Wed, 6 May 2020 11:23:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CX/V9Gf8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726480AbgEFLXg (ORCPT ); Wed, 6 May 2020 07:23:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:43955 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726897AbgEFLXg (ORCPT ); Wed, 6 May 2020 07:23:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588764215; 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; bh=sxASDUoH2mg/OWf8ncLB2g7lbzbXYW0W74S4Ym38kY4=; b=CX/V9Gf8rBUdSEjs3woaysCV9eyMcAA/1b1Xz6EnPBh8Tyw6Lx5P19yZw7+EGACX07WsjV MsuKNx5EkHhDSa0r0PjpRSoh8wwiHGRhx8xbnSVdxPlTx+o9qDUtRnUL3HN09hhtQpxVbN lmBFgCgJaJ7KMYm+t7W2ChRmUn6Y78I= 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-38-B0la5jEdOqShtYnvxui7Jg-1; Wed, 06 May 2020 07:23:33 -0400 X-MC-Unique: B0la5jEdOqShtYnvxui7Jg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD14B800687; Wed, 6 May 2020 11:23:31 +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 B80645D9C5; Wed, 6 May 2020 11:23:31 +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 046BNVI0027401; Wed, 6 May 2020 07:23:31 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 046BNV9i027397; Wed, 6 May 2020 07:23:31 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Wed, 6 May 2020 07:23:31 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Richard Henderson , Ivan Kokshaysky , Matt Turner , Greg Kroah-Hartman cc: linux-alpha@vger.kernel.org, Sinan Kaya , Arnd Bergmann , linux-serial@vger.kernel.org, linux-rtc@vger.kernel.org Subject: [PATCH 2/2] alpha: add a delay before serial port read Message-ID: 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 2.79 on 10.5.11.14 Sender: linux-rtc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rtc@vger.kernel.org The patch 92d7223a74235054f2aa7227d207d9c57f84dca0 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2") broke boot on the Alpha Avanti platform. The patch changes timing between accesses to the ISA bus, in particular, it reduces the time between "write" access and a subsequent "read" access. This causes lock-up when accessing the real time clock and serial ports. This patch fixes the serial ports by adding a small delay before the "inb" instruction. Signed-off-by: Mikulas Patocka Fixes: 92d7223a7423 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2") Cc: stable@vger.kernel.org # v4.17+ --- drivers/tty/serial/8250/8250_port.c | 4 ++++ 1 file changed, 4 insertions(+) Index: linux-stable/drivers/tty/serial/8250/8250_port.c =================================================================== --- linux-stable.orig/drivers/tty/serial/8250/8250_port.c 2020-05-06 08:25:19.000000000 +0200 +++ linux-stable/drivers/tty/serial/8250/8250_port.c 2020-05-06 09:04:17.000000000 +0200 @@ -442,6 +442,10 @@ static unsigned int mem32be_serial_in(st static unsigned int io_serial_in(struct uart_port *p, int offset) { +#ifdef CONFIG_ALPHA +/* we need a small delay, the Alpha Avanti chipset locks up with back-to-back accesses */ + ndelay(300); +#endif offset = offset << p->regshift; return inb(p->iobase + offset); }