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[patch] linux: mb() and friends again

To: Ralf Baechle <ralf@uni-koblenz.de>
Subject: [patch] linux: mb() and friends again
From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Date: Mon, 3 Jun 2002 18:45:49 +0200 (MET DST)
Cc: linux-mips@fnet.fr, linux-mips@oss.sgi.com
Organization: Technical University of Gdansk
Sender: owner-linux-mips@oss.sgi.com
Hello,

 There was a discussion some time ago upon my proposal of a clean-up of
mb() and related macros.  The conclusion was a rewrite is desireable, but
the patch wasn't accepted and no alternative was proposed.

 The need for the update is more and more crucial for me as I have more
and more code to apply to the tree that needs the macros be set somehow. 
If there is a design flaw, I'd like to know of it, if there is an
implementation problem, I'm willing to fix it.  I'm aware about peripheral
bus-specific coherency problems -- the patch is orthogonal to them and
only addresses the host bus.

 Here is an updated version I'm using currently.  It's fixed to apply
against the current tree and adds <asm-mips64/wbflush.h> for source code
compatibility.

  Maciej

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +

patch-mips-2.4.18-20020530-mb-wb-8
diff -up --recursive --new-file 
linux-mips-2.4.18-20020530.macro/arch/mips/config.in 
linux-mips-2.4.18-20020530/arch/mips/config.in
--- linux-mips-2.4.18-20020530.macro/arch/mips/config.in        2002-05-30 
02:57:35.000000000 +0000
+++ linux-mips-2.4.18-20020530/arch/mips/config.in      2002-06-02 
15:51:03.000000000 +0000
@@ -393,6 +393,11 @@ else
       fi
    fi
 fi
+if [ "$CONFIG_CPU_R3000" = "y" ]; then
+   define_bool CONFIG_CPU_HAS_SYNC n
+else
+   define_bool CONFIG_CPU_HAS_SYNC y
+fi
 endmenu
 
 mainmenu_option next_comment
diff -up --recursive --new-file 
linux-mips-2.4.18-20020530.macro/include/asm-mips/system.h 
linux-mips-2.4.18-20020530/include/asm-mips/system.h
--- linux-mips-2.4.18-20020530.macro/include/asm-mips/system.h  2002-05-28 
10:13:21.000000000 +0000
+++ linux-mips-2.4.18-20020530/include/asm-mips/system.h        2002-06-02 
15:51:03.000000000 +0000
@@ -18,9 +18,12 @@
 
 #include <linux/config.h>
 #include <asm/sgidefs.h>
-#include <asm/ptrace.h>
+
 #include <linux/kernel.h>
 
+#include <asm/addrspace.h>
+#include <asm/ptrace.h>
+
 __asm__ (
        ".macro\t__sti\n\t"
        ".set\tpush\n\t"
@@ -166,32 +169,58 @@ extern void __global_restore_flags(unsig
 #define local_irq_disable()    __cli()
 #define local_irq_enable()     __sti()
 
-/*
- * These are probably defined overly paranoid ...
- */
+#ifdef CONFIG_CPU_HAS_SYNC
+#define __sync()                               \
+       __asm__ __volatile__(                   \
+               ".set   push\n\t"               \
+               ".set   noreorder\n\t"          \
+               ".set   mips2\n\t"              \
+               "sync\n\t"                      \
+               ".set   pop"                    \
+               : /* no output */               \
+               : /* no input */                \
+               : "memory")
+#else
+#define __sync()       do { } while(0)
+#endif
+
+#define __fast_iob()                           \
+       __asm__ __volatile__(                   \
+               ".set   push\n\t"               \
+               ".set   noreorder\n\t"          \
+               "lw     $0,%0\n\t"              \
+               "nop\n\t"                       \
+               ".set   pop"                    \
+               : /* no output */               \
+               : "m" (*(int *)KSEG1)           \
+               : "memory")
+
+#define fast_wmb()     __sync()
+#define fast_rmb()     __sync()
+#define fast_mb()      __sync()
+#define fast_iob()                             \
+       do {                                    \
+               __sync();                       \
+               __fast_iob();                   \
+       } while (0)
+
 #ifdef CONFIG_CPU_HAS_WB
 
 #include <asm/wbflush.h>
-#define rmb()  do { } while(0)
-#define wmb()  wbflush()
-#define mb()   wbflush()
-
-#else /* CONFIG_CPU_HAS_WB  */
-
-#define mb()                                           \
-__asm__ __volatile__(                                  \
-       "# prevent instructions being moved around\n\t" \
-       ".set\tnoreorder\n\t"                           \
-       "# 8 nops to fool the R4400 pipeline\n\t"       \
-       "nop;nop;nop;nop;nop;nop;nop;nop\n\t"           \
-       ".set\treorder"                                 \
-       : /* no output */                               \
-       : /* no input */                                \
-       : "memory")
-#define rmb() mb()
-#define wmb() mb()
 
-#endif /* CONFIG_CPU_HAS_WB  */
+#define wmb()          fast_wmb()
+#define rmb()          fast_rmb()
+#define mb()           wbflush();
+#define iob()          wbflush();
+
+#else /* !CONFIG_CPU_HAS_WB */
+
+#define wmb()          fast_wmb()
+#define rmb()          fast_rmb()
+#define mb()           fast_mb()
+#define iob()          fast_iob()
+
+#endif /* !CONFIG_CPU_HAS_WB */
 
 #ifdef CONFIG_SMP
 #define smp_mb()       mb()
diff -up --recursive --new-file 
linux-mips-2.4.18-20020530.macro/include/asm-mips/wbflush.h 
linux-mips-2.4.18-20020530/include/asm-mips/wbflush.h
--- linux-mips-2.4.18-20020530.macro/include/asm-mips/wbflush.h 2001-09-07 
04:26:33.000000000 +0000
+++ linux-mips-2.4.18-20020530/include/asm-mips/wbflush.h       2002-02-04 
02:52:11.000000000 +0000
@@ -6,29 +6,30 @@
  * for more details.
  *
  * Copyright (c) 1998 Harald Koerfgen
+ * Copyright (C) 2002 Maciej W. Rozycki
  */
 #ifndef __ASM_MIPS_WBFLUSH_H
 #define __ASM_MIPS_WBFLUSH_H
 
 #include <linux/config.h>
 
-#if defined(CONFIG_CPU_HAS_WB)
-/*
- * R2000 or R3000
- */
-extern void (*__wbflush) (void);
+#ifdef CONFIG_CPU_HAS_WB
 
-#define wbflush() __wbflush()
+extern void (*__wbflush)(void);
+extern void wbflush_setup(void);
 
-#else
-/*
- * we don't need no stinkin' wbflush
- */
+#define wbflush()                      \
+       do {                            \
+               __sync();               \
+               __wbflush();            \
+       } while (0)
 
-#define wbflush()  do { } while(0)
+#else /* !CONFIG_CPU_HAS_WB */
 
-#endif
+#define wbflush_setup() do { } while (0)
 
-extern void wbflush_setup(void);
+#define wbflush() fast_iob()
+
+#endif /* !CONFIG_CPU_HAS_WB */
 
 #endif /* __ASM_MIPS_WBFLUSH_H */
diff -up --recursive --new-file 
linux-mips-2.4.18-20020530.macro/include/asm-mips64/system.h 
linux-mips-2.4.18-20020530/include/asm-mips64/system.h
--- linux-mips-2.4.18-20020530.macro/include/asm-mips64/system.h        
2002-05-28 10:13:22.000000000 +0000
+++ linux-mips-2.4.18-20020530/include/asm-mips64/system.h      2002-06-02 
15:55:32.000000000 +0000
@@ -12,9 +12,12 @@
 
 #include <linux/config.h>
 #include <asm/sgidefs.h>
-#include <asm/ptrace.h>
+
 #include <linux/kernel.h>
 
+#include <asm/addrspace.h>
+#include <asm/ptrace.h>
+
 __asm__ (
        ".macro\t__sti\n\t"
        ".set\tpush\n\t"
@@ -161,20 +164,37 @@ extern void __global_restore_flags(unsig
 #define local_irq_disable()    __cli()
 #define local_irq_enable()     __sti()
 
-/*
- * These are probably defined overly paranoid ...
- */
-#define mb()                                           \
-__asm__ __volatile__(                                  \
-       "# prevent instructions being moved around\n\t" \
-       ".set\tnoreorder\n\t"                           \
-       "sync\n\t"                                      \
-       ".set\treorder"                                 \
-       : /* no output */                               \
-       : /* no input */                                \
-       : "memory")
-#define rmb() mb()
-#define wmb() mb()
+#define __sync()                               \
+       __asm__ __volatile__(                   \
+               ".set   push\n\t"               \
+               ".set   noreorder\n\t"          \
+               "sync\n\t"                      \
+               ".set   pop"                    \
+               : /* no output */               \
+               : /* no input */                \
+               : "memory")
+
+#define fast_wmb()     __sync()
+#define fast_rmb()     __sync()
+#define fast_mb()      __sync()
+#define fast_iob()                             \
+       do {                                    \
+               __sync();                       \
+               __asm__ __volatile__(           \
+                       ".set   push\n\t"       \
+                       ".set   noreorder\n\t"  \
+                       "lw     $0,%0\n\t"      \
+                       "nop\n\t"               \
+                       ".set   pop"            \
+                       : /* no output */       \
+                       : "m" (*(int *)KSEG1)   \
+                       : "memory");            \
+       } while (0)
+
+#define wmb()          fast_wmb()
+#define rmb()          fast_rmb()
+#define mb()           fast_mb()
+#define iob()          fast_iob()
 
 #ifdef CONFIG_SMP
 #define smp_mb()       mb()
diff -up --recursive --new-file 
linux-mips-2.4.18-20020530.macro/include/asm-mips64/wbflush.h 
linux-mips-2.4.18-20020530/include/asm-mips64/wbflush.h
--- linux-mips-2.4.18-20020530.macro/include/asm-mips64/wbflush.h       
1970-01-01 00:00:00.000000000 +0000
+++ linux-mips-2.4.18-20020530/include/asm-mips64/wbflush.h     2002-05-31 
11:43:50.000000000 +0000
@@ -0,0 +1,18 @@
+/*
+ * Header file for using the wbflush routine
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 1998 Harald Koerfgen
+ * Copyright (C) 2002 Maciej W. Rozycki
+ */
+#ifndef __ASM_MIPS64_WBFLUSH_H
+#define __ASM_MIPS64_WBFLUSH_H
+
+#define wbflush_setup() do { } while (0)
+
+#define wbflush() fast_iob()
+
+#endif /* __ASM_MIPS64_WBFLUSH_H */


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