From patchwork Wed May 6 15:29:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 1284511 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-rtc-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=E8F6KArE; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49HLB21JZsz9sWY for ; Thu, 7 May 2020 01:29:46 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729573AbgEFP3p (ORCPT ); Wed, 6 May 2020 11:29:45 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:29897 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729689AbgEFP3o (ORCPT ); Wed, 6 May 2020 11:29:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588778982; 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=9VK2bwT1/tv3RtQTJg/KRhe8o13OTPTp5+7W2DtpmxU=; b=E8F6KArEnZCATTIWviRvquZtbvs0yucwEivslIQj/oiPez59X1NyYh5P/xoSg0i1eeyXFC fhSjOsUmyWVGX2mkbqG/Mn1PYJYx6HLsI2sfI3z4uJN/vHeoRG7rhQ0FTTSZoutRUh591d pR02YU62vJNxRlZo6LwYdKGuc0cBi3w= 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-392-Vd8GmeOLNIq77LXevHyuAw-1; Wed, 06 May 2020 11:29:39 -0400 X-MC-Unique: Vd8GmeOLNIq77LXevHyuAw-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 89D9086ABD9; Wed, 6 May 2020 15:29:31 +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 5D5D65D9C5; Wed, 6 May 2020 15:29:31 +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 046FTU8j016748; Wed, 6 May 2020 11:29:30 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 046FTTlA016744; Wed, 6 May 2020 11:29:29 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Wed, 6 May 2020 11:29:29 -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, Sinan Kaya , Arnd Bergmann , linux-serial@vger.kernel.org, linux-rtc@vger.kernel.org Subject: [PATCH 2/2 v2] alpha: add a delay before serial port read In-Reply-To: <20200506114711.GB3024358@kroah.com> Message-ID: References: <20200506114711.GB3024358@kroah.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 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 On Wed, 6 May 2020, Greg Kroah-Hartman wrote: > > 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 > > We really do not like #ifdef in .c files, especially ones that cause a > coding style violation :) > > Why can't you do this as a quirk for this specific chipset? You should > tie it to the serial port hardware type, not to the CPU type. > > thanks, > > greg k-h Do you want this patch? It enables the delay based on the specific PCI-ISA bridge. There is still "#if defined(CONFIG_ALPHA) && defined(CONFIG_PCI)" because if we want to reference a variable defined by the PCI subsystem in the arch/alpha tree, we must do it conditionally. If you want to get rid of these #ifs, please describe how. Mikulas From: Mikulas Patocka 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+ --- arch/alpha/include/asm/pci.h | 2 ++ arch/alpha/kernel/pci.c | 4 ++++ drivers/tty/serial/8250/8250_core.c | 7 +++++++ drivers/tty/serial/8250/8250_port.c | 3 +++ include/linux/serial_core.h | 1 + 5 files changed, 17 insertions(+) Index: linux-stable/include/linux/serial_core.h =================================================================== --- linux-stable.orig/include/linux/serial_core.h 2020-05-06 17:16:28.000000000 +0200 +++ linux-stable/include/linux/serial_core.h 2020-05-06 17:16:28.000000000 +0200 @@ -154,6 +154,7 @@ struct uart_port { /* quirks must be updated while holding port mutex */ #define UPQ_NO_TXEN_TEST BIT(0) +#define UPQ_DELAY_BEFORE_READ BIT(1) unsigned int read_status_mask; /* driver specific */ unsigned int ignore_status_mask; /* driver specific */ Index: linux-stable/drivers/tty/serial/8250/8250_core.c =================================================================== --- linux-stable.orig/drivers/tty/serial/8250/8250_core.c 2020-05-06 17:16:28.000000000 +0200 +++ linux-stable/drivers/tty/serial/8250/8250_core.c 2020-05-06 17:16:28.000000000 +0200 @@ -37,6 +37,9 @@ #ifdef CONFIG_SPARC #include #endif +#if defined(CONFIG_ALPHA) && defined(CONFIG_PCI) +#include +#endif #include @@ -490,6 +493,10 @@ static void univ8250_rsa_support(struct static inline void serial8250_apply_quirks(struct uart_8250_port *up) { up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0; +#if defined(CONFIG_ALPHA) && defined(CONFIG_PCI) + if (alpha_serial_port_needs_delay) + up->port.quirks |= UPQ_DELAY_BEFORE_READ; +#endif } static void __init serial8250_isa_init_ports(void) Index: linux-stable/arch/alpha/include/asm/pci.h =================================================================== --- linux-stable.orig/arch/alpha/include/asm/pci.h 2020-05-06 17:16:28.000000000 +0200 +++ linux-stable/arch/alpha/include/asm/pci.h 2020-05-06 17:16:28.000000000 +0200 @@ -97,4 +97,6 @@ extern void pci_adjust_legacy_attr(struc extern int pci_create_resource_files(struct pci_dev *dev); extern void pci_remove_resource_files(struct pci_dev *dev); +extern int alpha_serial_port_needs_delay; + #endif /* __ALPHA_PCI_H */ Index: linux-stable/arch/alpha/kernel/pci.c =================================================================== --- linux-stable.orig/arch/alpha/kernel/pci.c 2020-05-06 17:16:28.000000000 +0200 +++ linux-stable/arch/alpha/kernel/pci.c 2020-05-06 17:16:28.000000000 +0200 @@ -61,9 +61,13 @@ struct pci_controller *pci_isa_hose; * Quirks. */ +int alpha_serial_port_needs_delay = 0; +EXPORT_SYMBOL(alpha_serial_port_needs_delay); + static void quirk_isa_bridge(struct pci_dev *dev) { dev->class = PCI_CLASS_BRIDGE_ISA << 8; + alpha_serial_port_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 2020-05-06 17:16:28.000000000 +0200 +++ linux-stable/drivers/tty/serial/8250/8250_port.c 2020-05-06 17:16:32.000000000 +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); }