From patchwork Thu May 7 08:18:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 1285024 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=MJIe50Fj; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49HmZY5X68z9sRY for ; Thu, 7 May 2020 18:19:01 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725985AbgEGIS6 (ORCPT ); Thu, 7 May 2020 04:18:58 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:25454 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725849AbgEGIS5 (ORCPT ); Thu, 7 May 2020 04:18:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588839535; 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=qspgtcZm0CaRQEUxWr1T4kAFc2ZbtqSE5CP5g8UaW5Q=; b=MJIe50Fjc09lq9T7aDoDjpIwDlZoIT2kYlFlorab4JXQa7o+x7bI8lC45JZgvxT0O/A4E/ c46Yx8CKLpf5MiT0/66SmC4lL+PFl4vmlW5AuHSEcG+xx3RzYxY/gw7HmdveVbOE5MFd4T t94QMDYOonRkA0pJjNI/HX1eqxZmlbw= 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-243-WvjSostANmmgppxFTzBmzA-1; Thu, 07 May 2020 04:18:51 -0400 X-MC-Unique: WvjSostANmmgppxFTzBmzA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5C61419057A0; Thu, 7 May 2020 08:18:50 +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 30B9261527; Thu, 7 May 2020 08:18:49 +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 0478InHX007344; Thu, 7 May 2020 04:18:49 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 0478InYx007340; Thu, 7 May 2020 04:18:49 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Thu, 7 May 2020 04:18:49 -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: [PATCH 2/2 v4] alpha: add a delay before serial port read In-Reply-To: <20200506174528.GB3711921@kroah.com> Message-ID: References: <20200506114711.GB3024358@kroah.com> <20200506154938.GA3537174@kroah.com> <20200506160823.GA3559699@kroah.com> <20200506174528.GB3711921@kroah.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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: > On Wed, May 06, 2020 at 01:04:38PM -0400, Mikulas Patocka wrote: > > > > I've created this patch that adds a global macro/variable > > serial_port_needs_delay. I've also deleted UPQ_DELAY_BEFORE_READ and test > > serial_port_needs_delay directly in io_serial_in, so that the compiler > > will optimize it out on non-alpha architectures. > > That's not good, what about systems with hundreds of serial ports? I doubt that someone will conect hundreds of serial ports to such an old alpha machine :) > > > But, there is no other way to detect this based on hardware > > > signatures/types instead? That is usually the best way to do it, right? > > > > It's hard to detect Alpha without using '#ifdef CONFIG_ALPHA' :) The ISA > > serial port hardware is simple, so I think that you can't distinguish it > > just based on its behavior. > > The ISA serial port hardware does not have a unique vendor/product id > somewhere? Some other sort of definition that we can use to determine > exactly what type of system we are running on? AFAIK it doesn't. You can only distinguish 8250, 16550 and 16550A - but not the vendor. > > Index: linux-stable/drivers/tty/serial/8250/8250_port.c > > =================================================================== > > --- linux-stable.orig/drivers/tty/serial/8250/8250_port.c 2020-05-06 18:54:24.000000000 +0200 > > +++ linux-stable/drivers/tty/serial/8250/8250_port.c 2020-05-06 18:54:24.000000000 +0200 > > @@ -30,6 +30,7 @@ > > #include > > #include > > #include > > +#include > > > > #include > > #include > > @@ -442,6 +443,9 @@ static unsigned int mem32be_serial_in(st > > > > static unsigned int io_serial_in(struct uart_port *p, int offset) > > { > > + if (serial_port_needs_delay) > > + ndelay(300); > > Again, this should be a per-port thing, not all ports in the system are > this broken, right? > > thanks, > > greg k-h Here is the patch that uses per-port flag UPQ_DELAY_BEFORE_READ. The flag is activated if we have the specific PCI-ISA bridge and if the serial port is an ISA port. 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 | 3 +++ arch/alpha/kernel/pci.c | 4 ++++ drivers/tty/serial/8250/8250_core.c | 15 +++++++++------ drivers/tty/serial/8250/8250_port.c | 3 +++ include/linux/pci.h | 4 ++++ include/linux/serial_core.h | 1 + 6 files changed, 24 insertions(+), 6 deletions(-) Index: linux-stable/arch/alpha/include/asm/pci.h =================================================================== --- linux-stable.orig/arch/alpha/include/asm/pci.h 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/arch/alpha/include/asm/pci.h 2020-05-07 09:54:55.000000000 +0200 @@ -97,4 +97,7 @@ 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 serial_port_needs_delay; +#define serial_port_needs_delay serial_port_needs_delay + #endif /* __ALPHA_PCI_H */ Index: linux-stable/arch/alpha/kernel/pci.c =================================================================== --- linux-stable.orig/arch/alpha/kernel/pci.c 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/arch/alpha/kernel/pci.c 2020-05-07 09:54:55.000000000 +0200 @@ -61,9 +61,13 @@ struct pci_controller *pci_isa_hose; * Quirks. */ +int serial_port_needs_delay = 0; +EXPORT_SYMBOL(serial_port_needs_delay); + static void quirk_isa_bridge(struct pci_dev *dev) { dev->class = PCI_CLASS_BRIDGE_ISA << 8; + 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 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/drivers/tty/serial/8250/8250_port.c 2020-05-07 09:54:55.000000000 +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/include/linux/pci.h =================================================================== --- linux-stable.orig/include/linux/pci.h 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/include/linux/pci.h 2020-05-07 09:54:55.000000000 +0200 @@ -2384,6 +2384,10 @@ static inline bool pci_is_thunderbolt_at return false; } +#ifndef serial_port_needs_delay +#define serial_port_needs_delay 0 +#endif + #if defined(CONFIG_PCIEPORTBUS) || defined(CONFIG_EEH) void pci_uevent_ers(struct pci_dev *pdev, enum pci_ers_result err_type); #endif Index: linux-stable/drivers/tty/serial/8250/8250_core.c =================================================================== --- linux-stable.orig/drivers/tty/serial/8250/8250_core.c 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/drivers/tty/serial/8250/8250_core.c 2020-05-07 09:54:55.000000000 +0200 @@ -34,6 +34,7 @@ #include #include #include +#include #ifdef CONFIG_SPARC #include #endif @@ -487,9 +488,17 @@ 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; + if (serial_port_needs_delay && serial8250_isa_devs && up->port.dev == &serial8250_isa_devs->dev) + up->port.quirks |= UPQ_DELAY_BEFORE_READ; } static void __init serial8250_isa_init_ports(void) @@ -903,12 +912,6 @@ static struct platform_driver serial8250 }; /* - * 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; - -/* * serial8250_register_8250_port and serial8250_unregister_port allows for * 16x50 serial ports to be configured at run-time, to support PCMCIA * modems and PCI multiport cards. Index: linux-stable/include/linux/serial_core.h =================================================================== --- linux-stable.orig/include/linux/serial_core.h 2020-05-07 09:54:55.000000000 +0200 +++ linux-stable/include/linux/serial_core.h 2020-05-07 09:54:55.000000000 +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 */