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From: Mikulas Patocka <mpatocka@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Henderson <rth@twiddle.net>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Matt Turner <mattst88@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	alpha <linux-alpha@vger.kernel.org>,
	linux-serial@vger.kernel.org, linux-rtc@vger.kernel.org
Subject: [PATCH v4] alpha: add a barrier after outb, outw and outl
Date: Thu, 7 May 2020 11:46:44 -0400 (EDT)
Message-ID: <alpine.LRH.2.02.2005071145250.15191@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <CAK8P3a3UdCJL6C07_W7pkipT1Xmr_0G9hOy1S+YXbB4_tKt+gg@mail.gmail.com>

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 bug by adding a memory barrier after the functions
that access the ISA ports - outb, outw, outl. The barrier causes that
there is some delay between the write to an IO port and a subsequent read.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 92d7223a7423 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2")
Cc: stable@vger.kernel.org	# v4.17+

---
 arch/alpha/include/asm/io.h |    3 +++
 arch/alpha/kernel/io.c      |    3 +++
 2 files changed, 6 insertions(+)

Index: linux-stable/arch/alpha/include/asm/io.h
===================================================================
--- linux-stable.orig/arch/alpha/include/asm/io.h	2020-05-07 17:36:58.000000000 +0200
+++ linux-stable/arch/alpha/include/asm/io.h	2020-05-07 17:36:58.000000000 +0200
@@ -347,11 +347,13 @@ extern inline u16 inw(unsigned long port
 extern inline void outb(u8 b, unsigned long port)
 {
 	iowrite8(b, ioport_map(port, 1));
+	mb();
 }
 
 extern inline void outw(u16 b, unsigned long port)
 {
 	iowrite16(b, ioport_map(port, 2));
+	mb();
 }
 #endif
 
@@ -377,6 +379,7 @@ extern inline u32 inl(unsigned long port
 extern inline void outl(u32 b, unsigned long port)
 {
 	iowrite32(b, ioport_map(port, 4));
+	mb();
 }
 #endif
 
Index: linux-stable/arch/alpha/kernel/io.c
===================================================================
--- linux-stable.orig/arch/alpha/kernel/io.c	2020-05-07 17:36:58.000000000 +0200
+++ linux-stable/arch/alpha/kernel/io.c	2020-05-07 17:36:58.000000000 +0200
@@ -78,16 +78,19 @@ u32 inl(unsigned long port)
 void outb(u8 b, unsigned long port)
 {
 	iowrite8(b, ioport_map(port, 1));
+	mb();
 }
 
 void outw(u16 b, unsigned long port)
 {
 	iowrite16(b, ioport_map(port, 2));
+	mb();
 }
 
 void outl(u32 b, unsigned long port)
 {
 	iowrite32(b, ioport_map(port, 4));
+	mb();
 }
 
 EXPORT_SYMBOL(inb);


  parent reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-06 11:21 [PATCH 1/2] alpha: add a delay between RTC port write and read Mikulas Patocka
2020-05-06 14:20 ` Arnd Bergmann
2020-05-06 17:12   ` [PATCH 1/2 v2] alpha: add a delay to inb_p, inb_w and inb_l Mikulas Patocka
2020-05-07  8:06     ` [PATCH 1/2 v3] " Mikulas Patocka
2020-05-07  8:20       ` Greg Kroah-Hartman
2020-05-07 10:53         ` Mikulas Patocka
2020-05-07 13:30       ` Arnd Bergmann
2020-05-07 14:09         ` Mikulas Patocka
2020-05-07 15:08           ` Arnd Bergmann
2020-05-07 15:45             ` Mikulas Patocka
2020-05-07 15:46             ` Mikulas Patocka [this message]
2020-05-07 19:12               ` [PATCH v4] alpha: add a barrier after outb, outw and outl Arnd Bergmann
2020-05-10  1:27                 ` Maciej W. Rozycki
2020-05-10  1:25             ` [PATCH 1/2 v3] alpha: add a delay to inb_p, inb_w and inb_l Maciej W. Rozycki
2020-05-10 18:50               ` Mikulas Patocka
2020-05-11 14:58                 ` Maciej W. Rozycki
2020-05-12 19:35                   ` Mikulas Patocka
2020-05-13 14:41                   ` Ivan Kokshaysky
2020-05-13 16:13                     ` Greg Kroah-Hartman
2020-05-13 17:17                     ` Maciej W. Rozycki
2020-05-22 13:03                       ` Mikulas Patocka
2020-05-22 13:37                         ` Maciej W. Rozycki
2020-05-22 13:26                     ` Mikulas Patocka
2020-05-22 20:00                       ` Mikulas Patocka
2020-05-23 10:26                         ` [PATCH v4] alpha: fix memory barriers so that they conform to the specification Mikulas Patocka
2020-05-23 15:10                           ` Ivan Kokshaysky
2020-05-23 15:34                             ` Mikulas Patocka
2020-05-23 15:37                               ` [PATCH v5] " Mikulas Patocka
2020-05-24 14:54                                 ` Maciej W. Rozycki
2020-05-25 13:56                                   ` Mikulas Patocka
2020-05-25 14:07                                     ` Arnd Bergmann
2020-05-25 14:45                                     ` Maciej W. Rozycki
2020-05-25 15:53                                       ` [PATCH v6] " Mikulas Patocka
2020-05-26 14:47                                         ` [PATCH v7] " Mikulas Patocka
2020-05-27  0:18                                           ` Maciej W. Rozycki
2020-06-08  6:58                                             ` Mikulas Patocka
2020-06-08 23:49                                               ` Matt Turner
2020-05-25 15:54                                       ` [PATCH v5] " Mikulas Patocka
2020-05-25 16:39                                         ` Maciej W. Rozycki
2020-05-26 14:48                                           ` Mikulas Patocka
2020-05-27  0:23                                             ` Maciej W. Rozycki
2020-05-23 16:44                               ` [PATCH v4] " Maciej W. Rozycki
2020-05-23 17:09                                 ` Mikulas Patocka
2020-05-23 19:27                                   ` Maciej W. Rozycki
2020-05-23 20:11                                     ` Mikulas Patocka

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