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[mips] Work around bad code generation for <asm/io.h> (Ralf Baechle). 

svn path=/dists/trunk/linux-2.6/; revision=6191
This commit is contained in:
Martin Michlmayr 2006-03-15 13:56:35 +00:00
parent 4ba399e133
commit 319b2a385e
3 changed files with 61 additions and 0 deletions
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1
debian/changelog vendored
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@ -13,6 +13,7 @@ linux-2.6 (2.6.15+2.6.16-rc6-0experimental.1) UNRELEASED; urgency=low
* [mips] SB1: Support for 1480 ethernet (Broadcom).
* [mips] SB1: Support for NAPI (Tom Rix).
* [mips] SB1: DUART support (Broadcom).
* [mips] Work around bad code generation for <asm/io.h> (Ralf Baechle).
[ dann frazier ]
* [ia64] use yaird on ia64 until #341181 is fixed

59
debian/patches/mips-io-bad-code.patch vendored Normal file
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@ -0,0 +1,59 @@
From: linux-mips@linux-mips.org
Date: Wed, 15 Mar 2006 11:28:15 +0000
To: git-commits@linux-mips.org
Subject: [MIPS] Work around bad code generation for <asm/io.h>.
Author: Ralf Baechle <ralf@linux-mips.org> Wed Mar 15 11:36:31 2006 +0000
Commit: 6a186683e0a3d51836b6ef6b971508861c7002b5
Gitweb: http://www.linux-mips.org/g/linux/6a186683
Branch: master
If a call to set_io_port_base() was being followed by usage of
mips_io_port_base in the same function gcc was possibly using the old
value due to some clever abuse of const. Adding a barrier will keep
the optimization and result in correct code with latest gcc.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
---
include/asm-mips/io.h | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/include/asm-mips/io.h b/include/asm-mips/io.h
index 5c6d6ab..02995ad 100644
--- a/include/asm-mips/io.h
+++ b/include/asm-mips/io.h
@@ -4,7 +4,7 @@
* for more details.
*
* Copyright (C) 1994, 1995 Waldorf GmbH
- * Copyright (C) 1994 - 2000 Ralf Baechle
+ * Copyright (C) 1994 - 2000, 06 Ralf Baechle
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
* Copyright (C) 2004, 2005 MIPS Technologies, Inc. All rights reserved.
* Author: Maciej W. Rozycki <macro@mips.com>
@@ -103,8 +103,20 @@
*/
extern const unsigned long mips_io_port_base;
-#define set_io_port_base(base) \
- do { * (unsigned long *) &mips_io_port_base = (base); } while (0)
+/*
+ * Gcc will generate code to load the value of mips_io_port_base after each
+ * function call which may be fairly wasteful in some cases. So we don't
+ * play quite by the book. We tell gcc mips_io_port_base is a long variable
+ * which solves the code generation issue. Now we need to violate the
+ * aliasing rules a little to make initialization possible and finally we
+ * will need the barrier() to fight side effects of the aliasing chat.
+ * This trickery will eventually collapse under gcc's optimizer. Oh well.
+ */
+static inline void set_io_port_base(unsigned long base)
+{
+ * (unsigned long *) &mips_io_port_base;
+ barrier();
+}
/*
* Thanks to James van Artsdalen for a better timing-fix than

1
debian/patches/series/0experimental.1 vendored
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@ -23,5 +23,6 @@
+ mips-sb1-eth-1480.patch
+ mips-sb1-eth-napi.patch
+ mips-sb1-duart.patch
+ mips-io-bad-code.patch
+ s390-drivers-ccw-uevent-modalias.patch
+ s390-drivers-ccw-uevent-cleanup.patch