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 E479EC4724C for ; Thu, 7 May 2020 14:04:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF9B7208DB for ; Thu, 7 May 2020 14:04:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="H0KEu1eb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726519AbgEGOEG (ORCPT ); Thu, 7 May 2020 10:04:06 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:34102 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727975AbgEGOEF (ORCPT ); Thu, 7 May 2020 10:04:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588860243; 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=bKInnM6YzoqwwNpgvmY4EEnrQSmK0daesOkKkAujNxw=; b=H0KEu1ebaBiLVecXxEukLs8qpg/fazPiuVwOxjnBxeYUO7RcIRmhEbkNH9T1ceJZHpeKK7 SUX9O95LznHkkL+e0zDRRA64hHOl0L4Bf/zNdcte+1lC+6hFBCFHOZ4v8ZAO0rrAPFJfEC ZO5Zlvdk5mlx05FRQOjNPiovEGAZOPc= 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-48-thFf8rfkMv6e58E42wC3Yg-1; Thu, 07 May 2020 10:03:56 -0400 X-MC-Unique: thFf8rfkMv6e58E42wC3Yg-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 973501895950; Thu, 7 May 2020 14:03:54 +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 594711FBCD; Thu, 7 May 2020 14:03:54 +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 047E3rGw005009; Thu, 7 May 2020 10:03:53 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 047E3rpZ005006; Thu, 7 May 2020 10:03:53 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Thu, 7 May 2020 10:03:53 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Greg Kroah-Hartman cc: Richard Henderson , Ivan Kokshaysky , Matt Turner , linux-alpha@vger.kernel.org, Arnd Bergmann , linux-serial@vger.kernel.org, linux-rtc@vger.kernel.org Subject: Re: [PATCH 2/2 v5] alpha: add a delay before serial port read In-Reply-To: <20200507135839.GA1803635@kroah.com> Message-ID: References: <20200506154938.GA3537174@kroah.com> <20200506160823.GA3559699@kroah.com> <20200506174528.GB3711921@kroah.com> <20200507085201.GA1097552@kroah.com> <20200507111037.GB1490467@kroah.com> <20200507135839.GA1803635@kroah.com> 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-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Thu, 7 May 2020, Greg Kroah-Hartman wrote: > On Thu, May 07, 2020 at 08:57:09AM -0400, Mikulas Patocka wrote: > > 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. > > > > We introduce a global variable > > alpha_has_broken_serial_ports_and_needs_delay - it is defined on Alpha and > > it is set to 1 if we have the specific PCI-ISA bridge where this bug > > occurs. We also introduce a new per-port flag UPQ_DELAY_BEFORE_READ, the > > flag is set if alpha_has_broken_serial_ports_and_needs_delay is set and if > > the serial port is an ISA port. > > > > 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+ > > > > --- > > arch/alpha/include/asm/serial.h | 5 +++++ > > arch/alpha/kernel/pci.c | 5 +++++ > > drivers/tty/serial/8250/8250_core.c | 17 +++++++++++------ > > drivers/tty/serial/8250/8250_port.c | 3 +++ > > include/linux/serial_core.h | 1 + > > 5 files changed, 25 insertions(+), 6 deletions(-) > > > > Index: linux-stable/arch/alpha/kernel/pci.c > > =================================================================== > > --- linux-stable.orig/arch/alpha/kernel/pci.c 2020-05-07 09:57:02.000000000 +0200 > > +++ linux-stable/arch/alpha/kernel/pci.c 2020-05-07 14:30:07.000000000 +0200 > > @@ -24,6 +24,7 @@ > > #include > > #include > > #include > > +#include > > > > #include "proto.h" > > #include "pci_impl.h" > > @@ -61,9 +62,13 @@ struct pci_controller *pci_isa_hose; > > * Quirks. > > */ > > > > +int alpha_has_broken_serial_ports_and_needs_delay = 0; > > +EXPORT_SYMBOL(alpha_has_broken_serial_ports_and_needs_delay); > > + > > static void quirk_isa_bridge(struct pci_dev *dev) > > { > > dev->class = PCI_CLASS_BRIDGE_ISA << 8; > > + alpha_has_broken_serial_ports_and_needs_delay = 1; > > } > > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82378, quirk_isa_bridge); > > > > Index: linux-stable/drivers/tty/serial/8250/8250_port.c > > =================================================================== > > --- linux-stable.orig/drivers/tty/serial/8250/8250_port.c 2020-05-07 09:57:02.000000000 +0200 > > +++ linux-stable/drivers/tty/serial/8250/8250_port.c 2020-05-07 09:57:02.000000000 +0200 > > @@ -442,6 +442,9 @@ static unsigned int mem32be_serial_in(st > > > > static unsigned int io_serial_in(struct uart_port *p, int offset) > > { > > + if (unlikely(p->quirks & UPQ_DELAY_BEFORE_READ)) > > + ndelay(300); > > + > > offset = offset << p->regshift; > > return inb(p->iobase + offset); > > } > > Index: linux-stable/drivers/tty/serial/8250/8250_core.c > > =================================================================== > > --- linux-stable.orig/drivers/tty/serial/8250/8250_core.c 2020-05-07 09:57:02.000000000 +0200 > > +++ linux-stable/drivers/tty/serial/8250/8250_core.c 2020-05-07 14:34:16.000000000 +0200 > > @@ -487,9 +487,20 @@ static void univ8250_rsa_support(struct > > #define univ8250_rsa_support(x) do { } while (0) > > #endif /* CONFIG_SERIAL_8250_RSA */ > > > > +/* > > + * This "device" covers _all_ ISA 8250-compatible serial devices listed > > + * in the table in include/asm/serial.h > > + */ > > +static struct platform_device *serial8250_isa_devs; > > + > > static inline void serial8250_apply_quirks(struct uart_8250_port *up) > > { > > up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0; > > +#ifdef alpha_has_broken_serial_ports_and_needs_delay > > That is a symbol, not a define, how does that work? > > greg k-h That's both the symbol and a define - see this part of the patch: Mikulas Index: linux-stable/arch/alpha/include/asm/serial.h =================================================================== --- linux-stable.orig/arch/alpha/include/asm/serial.h 2020-02-07 11:52:16.000000000 +0100 +++ linux-stable/arch/alpha/include/asm/serial.h 2020-05-07 14:48:21.000000000 +0200 @@ -28,3 +28,8 @@ { 0, BASE_BAUD, 0x2F8, 3, STD_COM_FLAGS }, /* ttyS1 */ \ { 0, BASE_BAUD, 0x3E8, 4, STD_COM_FLAGS }, /* ttyS2 */ \ { 0, BASE_BAUD, 0x2E8, 3, STD_COM4_FLAGS }, /* ttyS3 */ + +#ifdef CONFIG_PCI +extern int alpha_has_broken_serial_ports_and_needs_delay; +#define alpha_has_broken_serial_ports_and_needs_delay alpha_has_broken_serial_ports_and_needs_delay +#endif