Re: [PATCH] I/O space write barrier

From: Jesse Barnes
Date: Wed Sep 29 2004 - 18:01:41 EST

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On Monday, September 27, 2004 11:03 am, Jesse Barnes wrote:
> Received a few comments and no complaints, so I'm sending this patch in for
> inclusion.

This one fixes up the documentation a bit, but is otherwise the same.

Signed-off-by: Jesse Barnes <jbarnes@xxxxxxx>

Jesse
diff -Nru a/Documentation/DocBook/deviceiobook.tmpl b/Documentation/DocBook/deviceiobook.tmpl
--- a/Documentation/DocBook/deviceiobook.tmpl 2004-09-29 15:51:10 -07:00
+++ b/Documentation/DocBook/deviceiobook.tmpl 2004-09-29 15:51:10 -07:00
@@ -147,8 +147,7 @@
compiler is not permitted to reorder the I/O sequence. When the
ordering can be compiler optimised, you can use <function>
__readb</function> and friends to indicate the relaxed ordering. Use
- this with care. The <function>rmb</function> provides a read memory
- barrier. The <function>wmb</function> provides a write memory barrier.
+ this with care.
</para>

<para>
@@ -159,10 +158,72 @@
asynchronously. A driver author must issue a read from the same
device to ensure that writes have occurred in the specific cases the
author cares. This kind of property cannot be hidden from driver
- writers in the API.
+ writers in the API. In some cases, the read used to flush the device
+ may be expected to fail (if the card is resetting, for example). In
+ that case, the read should be done from config space, which is
+ guaranteed to soft-fail if the card doesn't respond.
</para>

<para>
+ The following is an example of flushing a write to a device when
+ the driver would like to ensure the write's effects are visible prior
+ to continuing execution.
+ </para>
+
+<programlisting>
+static inline void
+qla1280_disable_intrs(struct scsi_qla_host *ha)
+{
+ struct device_reg *reg;
+
+ reg = ha->iobase;
+ /* disable risc and host interrupts */
+ WRT_REG_WORD(&reg->ictrl, 0);
+ /*
+ * The following read will ensure that the above write
+ * has been received by the device before we return from this
+ * function.
+ */
+ RD_REG_WORD(&reg->ictrl);
+ ha->flags.ints_enabled = 0;
+}
+</programlisting>
+
+ <para>
+ In addition to write posting, on some large multiprocessing systems
+ (e.g. SGI Challenge, Origin and Altix machines) posted writes won't
+ be strongly ordered coming from different CPUs. Thus it's important
+ to properly protect parts of your driver that do memory-mapped writes
+ with locks and use the <function>mmiowb</function> to make sure they
+ arrive in the order intended.
+ </para>
+
+ <para>
+ Generally, one should use <function>mmiowb</function> prior to
+ releasing a spinlock that protects regions using <function>writeb
+ </function> or similar functions that aren't surrounded by <function>
+ readb</function> calls, which will ensure ordering and flushing. The
+ following example (again from qla1280.c) illustrates its use.
+ </para>
+
+<programlisting>
+ sp->flags |= SRB_SENT;
+ ha->actthreads++;
+ WRT_REG_WORD(&reg->mailbox4, ha->req_ring_index);
+
+ /*
+ * A Memory Mapped I/O Write Barrier is needed to ensure that this write
+ * of the request queue in register is ordered ahead of writes issued
+ * after this one by other CPUs. Access to the register is protected
+ * by the host_lock. Without the mmiowb, however, it is possible for
+ * this CPU to release the host lock, another CPU acquire the host lock,
+ * and write to the request queue in, and have the second write make it
+ * to the chip first.
+ */
+ mmiowb(); /* posted write ordering */
+</programlisting>
+
+ <para>
PCI ordering rules also guarantee that PIO read responses arrive
after any outstanding DMA writes on that bus, since for some devices
the result of a <function>readb</function> call may signal to the
@@ -171,7 +232,9 @@
<function>readb</function> call has no relation to any previous DMA
writes performed by the device. The driver can use
<function>readb_relaxed</function> for these cases, although only
- some platforms will honor the relaxed semantics.
+ some platforms will honor the relaxed semantics. Using the relaxed
+ read functions will provide significant performance benefits on
+ platforms that support it.
</para>
</sect1>

diff -Nru a/Documentation/io_ordering.txt b/Documentation/io_ordering.txt
--- a/Documentation/io_ordering.txt 2004-09-29 15:51:10 -07:00
+++ /dev/null Wed Dec 31 16:00:00 196900
@@ -1,47 +0,0 @@
-On some platforms, so-called memory-mapped I/O is weakly ordered. On such
-platforms, driver writers are responsible for ensuring that I/O writes to
-memory-mapped addresses on their device arrive in the order intended. This is
-typically done by reading a 'safe' device or bridge register, causing the I/O
-chipset to flush pending writes to the device before any reads are posted. A
-driver would usually use this technique immediately prior to the exit of a
-critical section of code protected by spinlocks. This would ensure that
-subsequent writes to I/O space arrived only after all prior writes (much like a
-memory barrier op, mb(), only with respect to I/O).
-
-A more concrete example from a hypothetical device driver:
-
- ...
-CPU A: spin_lock_irqsave(&dev_lock, flags)
-CPU A: val = readl(my_status);
-CPU A: ...
-CPU A: writel(newval, ring_ptr);
-CPU A: spin_unlock_irqrestore(&dev_lock, flags)
- ...
-CPU B: spin_lock_irqsave(&dev_lock, flags)
-CPU B: val = readl(my_status);
-CPU B: ...
-CPU B: writel(newval2, ring_ptr);
-CPU B: spin_unlock_irqrestore(&dev_lock, flags)
- ...
-
-In the case above, the device may receive newval2 before it receives newval,
-which could cause problems. Fixing it is easy enough though:
-
- ...
-CPU A: spin_lock_irqsave(&dev_lock, flags)
-CPU A: val = readl(my_status);
-CPU A: ...
-CPU A: writel(newval, ring_ptr);
-CPU A: (void)readl(safe_register); /* maybe a config register? */
-CPU A: spin_unlock_irqrestore(&dev_lock, flags)
- ...
-CPU B: spin_lock_irqsave(&dev_lock, flags)
-CPU B: val = readl(my_status);
-CPU B: ...
-CPU B: writel(newval2, ring_ptr);
-CPU B: (void)readl(safe_register); /* maybe a config register? */
-CPU B: spin_unlock_irqrestore(&dev_lock, flags)
-
-Here, the reads from safe_register will cause the I/O chipset to flush any
-pending writes before actually posting the read to the chipset, preventing
-possible data corruption.
diff -Nru a/arch/ia64/sn/io/machvec/iomv.c b/arch/ia64/sn/io/machvec/iomv.c
--- a/arch/ia64/sn/io/machvec/iomv.c 2004-09-29 15:51:10 -07:00
+++ b/arch/ia64/sn/io/machvec/iomv.c 2004-09-29 15:51:10 -07:00
@@ -54,23 +54,19 @@
EXPORT_SYMBOL(sn_io_addr);

/**
- * sn_mmiob - I/O space memory barrier
+ * __sn_mmiowb - I/O space write barrier
*
- * Acts as a memory mapped I/O barrier for platforms that queue writes to
- * I/O space. This ensures that subsequent writes to I/O space arrive after
- * all previous writes. For most ia64 platforms, this is a simple
- * 'mf.a' instruction. For other platforms, mmiob() may have to read
- * a chipset register to ensure ordering.
+ * See include/asm-ia64/io.h and Documentation/DocBook/deviceiobook.tmpl
+ * for details.
*
* On SN2, we wait for the PIO_WRITE_STATUS SHub register to clear.
* See PV 871084 for details about the WAR about zero value.
*
*/
-void
-sn_mmiob (void)
+void __sn_mmiowb(void)
{
while ((((volatile unsigned long) (*pda->pio_write_status_addr)) & SH_PIO_WRITE_STATUS_0_PENDING_WRITE_COUNT_MASK) !=
SH_PIO_WRITE_STATUS_0_PENDING_WRITE_COUNT_MASK)
cpu_relax();
}
-EXPORT_SYMBOL(sn_mmiob);
+EXPORT_SYMBOL(__sn_mmiowb);
diff -Nru a/include/asm-alpha/io.h b/include/asm-alpha/io.h
--- a/include/asm-alpha/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-alpha/io.h 2004-09-29 15:51:10 -07:00
@@ -489,6 +489,8 @@
#define readl_relaxed(addr) __raw_readl(addr)
#define readq_relaxed(addr) __raw_readq(addr)

+#define mmiowb()
+
/*
* String version of IO memory access ops:
*/
diff -Nru a/include/asm-arm/io.h b/include/asm-arm/io.h
--- a/include/asm-arm/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-arm/io.h 2004-09-29 15:51:10 -07:00
@@ -135,6 +135,8 @@
extern void _memcpy_toio(unsigned long, const void *, size_t);
extern void _memset_io(unsigned long, int, size_t);

+#define mmiowb()
+
/*
* Memory access primitives
* ------------------------
diff -Nru a/include/asm-arm26/io.h b/include/asm-arm26/io.h
--- a/include/asm-arm26/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-arm26/io.h 2004-09-29 15:51:10 -07:00
@@ -320,6 +320,8 @@
#define writesw(p,d,l) __readwrite_bug("writesw")
#define writesl(p,d,l) __readwrite_bug("writesl")

+#define mmiowb()
+
/* the following macro is depreciated */
#define ioaddr(port) __ioaddr((port))

diff -Nru a/include/asm-cris/io.h b/include/asm-cris/io.h
--- a/include/asm-cris/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-cris/io.h 2004-09-29 15:51:10 -07:00
@@ -56,6 +56,8 @@
#define __raw_writew writew
#define __raw_writel writel

+#define mmiowb()
+
#define memset_io(a,b,c) memset((void *)(a),(b),(c))
#define memcpy_fromio(a,b,c) memcpy((a),(void *)(b),(c))
#define memcpy_toio(a,b,c) memcpy((void *)(a),(b),(c))
diff -Nru a/include/asm-h8300/io.h b/include/asm-h8300/io.h
--- a/include/asm-h8300/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-h8300/io.h 2004-09-29 15:51:10 -07:00
@@ -200,6 +200,8 @@
#define memcpy_fromio(a,b,c) memcpy((a),(void *)(b),(c))
#define memcpy_toio(a,b,c) memcpy((void *)(a),(b),(c))

+#define mmiowb()
+
#define inb(addr) ((h8300_buswidth(addr))?readw((addr) & ~1) & 0xff:readb(addr))
#define inw(addr) _swapw(readw(addr))
#define inl(addr) _swapl(readl(addr))
diff -Nru a/include/asm-i386/io.h b/include/asm-i386/io.h
--- a/include/asm-i386/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-i386/io.h 2004-09-29 15:51:10 -07:00
@@ -178,6 +178,8 @@
#define __raw_writew writew
#define __raw_writel writel

+#define mmiowb()
+
static inline void memset_io(volatile void __iomem *addr, unsigned char val, int count)
{
memset((void __force *) addr, val, count);
diff -Nru a/include/asm-ia64/io.h b/include/asm-ia64/io.h
--- a/include/asm-ia64/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/io.h 2004-09-29 15:51:10 -07:00
@@ -91,6 +91,20 @@
*/
#define __ia64_mf_a() ia64_mfa()

+/**
+ * __ia64_mmiowb - I/O write barrier
+ *
+ * Ensure ordering of I/O space writes. This will make sure that writes
+ * following the barrier will arrive after all previous writes. For most
+ * ia64 platforms, this is a simple 'mf.a' instruction.
+ *
+ * See Documentation/DocBook/deviceiobook.tmpl for more information.
+ */
+static inline void __ia64_mmiowb(void)
+{
+ ia64_mfa();
+}
+
static inline const unsigned long
__ia64_get_io_port_base (void)
{
@@ -267,6 +281,7 @@
#define __outb platform_outb
#define __outw platform_outw
#define __outl platform_outl
+#define __mmiowb platform_mmiowb

#define inb(p) __inb(p)
#define inw(p) __inw(p)
@@ -280,6 +295,7 @@
#define outsb(p,s,c) __outsb(p,s,c)
#define outsw(p,s,c) __outsw(p,s,c)
#define outsl(p,s,c) __outsl(p,s,c)
+#define mmiowb() __mmiowb()

/*
* The address passed to these functions are ioremap()ped already.
diff -Nru a/include/asm-ia64/machvec.h b/include/asm-ia64/machvec.h
--- a/include/asm-ia64/machvec.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/machvec.h 2004-09-29 15:51:10 -07:00
@@ -62,6 +62,7 @@
typedef void ia64_mv_outb_t (unsigned char, unsigned long);
typedef void ia64_mv_outw_t (unsigned short, unsigned long);
typedef void ia64_mv_outl_t (unsigned int, unsigned long);
+typedef void ia64_mv_mmiowb_t (void);
typedef unsigned char ia64_mv_readb_t (void *);
typedef unsigned short ia64_mv_readw_t (void *);
typedef unsigned int ia64_mv_readl_t (void *);
@@ -130,6 +131,7 @@
# define platform_outb ia64_mv.outb
# define platform_outw ia64_mv.outw
# define platform_outl ia64_mv.outl
+# define platform_mmiowb ia64_mv.mmiowb
# define platform_readb ia64_mv.readb
# define platform_readw ia64_mv.readw
# define platform_readl ia64_mv.readl
@@ -176,6 +178,7 @@
ia64_mv_outb_t *outb;
ia64_mv_outw_t *outw;
ia64_mv_outl_t *outl;
+ ia64_mv_mmiowb_t *mmiowb;
ia64_mv_readb_t *readb;
ia64_mv_readw_t *readw;
ia64_mv_readl_t *readl;
@@ -218,6 +221,7 @@
platform_outb, \
platform_outw, \
platform_outl, \
+ platform_mmiowb, \
platform_readb, \
platform_readw, \
platform_readl, \
@@ -343,6 +347,9 @@
#endif
#ifndef platform_outl
# define platform_outl __ia64_outl
+#endif
+#ifndef platform_mmiowb
+# define platform_mmiowb __ia64_mmiowb
#endif
#ifndef platform_readb
# define platform_readb __ia64_readb
diff -Nru a/include/asm-ia64/machvec_init.h b/include/asm-ia64/machvec_init.h
--- a/include/asm-ia64/machvec_init.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/machvec_init.h 2004-09-29 15:51:10 -07:00
@@ -12,6 +12,7 @@
extern ia64_mv_outb_t __ia64_outb;
extern ia64_mv_outw_t __ia64_outw;
extern ia64_mv_outl_t __ia64_outl;
+extern ia64_mv_mmiowb_t __ia64_mmiowb;
extern ia64_mv_readb_t __ia64_readb;
extern ia64_mv_readw_t __ia64_readw;
extern ia64_mv_readl_t __ia64_readl;
diff -Nru a/include/asm-ia64/machvec_sn2.h b/include/asm-ia64/machvec_sn2.h
--- a/include/asm-ia64/machvec_sn2.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/machvec_sn2.h 2004-09-29 15:51:10 -07:00
@@ -49,6 +49,7 @@
extern ia64_mv_outb_t __sn_outb;
extern ia64_mv_outw_t __sn_outw;
extern ia64_mv_outl_t __sn_outl;
+extern ia64_mv_mmiowb_t __sn_mmiowb;
extern ia64_mv_readb_t __sn_readb;
extern ia64_mv_readw_t __sn_readw;
extern ia64_mv_readl_t __sn_readl;
@@ -92,6 +93,7 @@
#define platform_outb __sn_outb
#define platform_outw __sn_outw
#define platform_outl __sn_outl
+#define platform_mmiowb __sn_mmiowb
#define platform_readb __sn_readb
#define platform_readw __sn_readw
#define platform_readl __sn_readl
diff -Nru a/include/asm-ia64/sn/io.h b/include/asm-ia64/sn/io.h
--- a/include/asm-ia64/sn/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/sn/io.h 2004-09-29 15:51:10 -07:00
@@ -58,8 +58,8 @@
#include <asm/sn/sn2/shubio.h>

/*
- * Used to ensure write ordering (like mb(), but for I/O space)
+ * Used to ensure write ordering
*/
-extern void sn_mmiob(void);
+extern void __sn_mmiowb(void);

#endif /* _ASM_IA64_SN_IO_H */
diff -Nru a/include/asm-ia64/sn/sn2/io.h b/include/asm-ia64/sn/sn2/io.h
--- a/include/asm-ia64/sn/sn2/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ia64/sn/sn2/io.h 2004-09-29 15:51:10 -07:00
@@ -11,8 +11,10 @@
#include <linux/compiler.h>
#include <asm/intrinsics.h>

-extern void * sn_io_addr(unsigned long port) __attribute_const__; /* Forward definition */
-extern void sn_mmiob(void); /* Forward definition */
+/* Forward declarations */
+struct device;
+extern void *sn_io_addr(unsigned long port) __attribute_const__;
+extern void __sn_mmiowb(void);

#define __sn_mf_a() ia64_mfa()

@@ -91,7 +93,7 @@

if ((addr = sn_io_addr(port))) {
*addr = val;
- sn_mmiob();
+ __sn_mmiowb();
}
}

@@ -102,7 +104,7 @@

if ((addr = sn_io_addr(port))) {
*addr = val;
- sn_mmiob();
+ __sn_mmiowb();
}
}

@@ -113,7 +115,7 @@

if ((addr = sn_io_addr(port))) {
*addr = val;
- sn_mmiob();
+ __sn_mmiowb();
}
}

diff -Nru a/include/asm-m32r/io.h b/include/asm-m32r/io.h
--- a/include/asm-m32r/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-m32r/io.h 2004-09-29 15:51:10 -07:00
@@ -150,6 +150,9 @@
#define __raw_readb readb
#define __raw_readw readw
#define __raw_readl readl
+#define readb_relaxed readb
+#define readw_relaxed readw
+#define readl_relaxed readl

#define writeb(val, addr) _writeb((val), (unsigned long)(addr))
#define writew(val, addr) _writew((val), (unsigned long)(addr))
@@ -157,6 +160,8 @@
#define __raw_writeb writeb
#define __raw_writew writew
#define __raw_writel writel
+
+#define mmiowb()

#define flush_write_buffers() do { } while (0) /* M32R_FIXME */

diff -Nru a/include/asm-m68k/io.h b/include/asm-m68k/io.h
--- a/include/asm-m68k/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-m68k/io.h 2004-09-29 15:51:10 -07:00
@@ -306,6 +306,7 @@
#endif
#endif /* CONFIG_PCI */

+#define mmiowb()

static inline void *ioremap(unsigned long physaddr, unsigned long size)
{
diff -Nru a/include/asm-m68knommu/io.h b/include/asm-m68knommu/io.h
--- a/include/asm-m68knommu/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-m68knommu/io.h 2004-09-29 15:51:10 -07:00
@@ -102,6 +102,8 @@
*bp++ = _swapl(*ap);
}

+#define mmiowb()
+
/*
* make the short names macros so specific devices
* can override them as required
diff -Nru a/include/asm-mips/io.h b/include/asm-mips/io.h
--- a/include/asm-mips/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-mips/io.h 2004-09-29 15:51:10 -07:00
@@ -290,6 +290,10 @@
#define __raw_writeb(b,addr) ((*(volatile unsigned char *)(addr)) = (b))
#define __raw_writew(w,addr) ((*(volatile unsigned short *)(addr)) = (w))
#define __raw_writel(l,addr) ((*(volatile unsigned int *)(addr)) = (l))
+
+/* Depends on MIPS III instruction set */
+#define mmiowb() asm volatile ("sync" ::: "memory")
+
#ifdef CONFIG_MIPS32
#define ____raw_writeq(val,addr) \
({ \
diff -Nru a/include/asm-parisc/io.h b/include/asm-parisc/io.h
--- a/include/asm-parisc/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-parisc/io.h 2004-09-29 15:51:10 -07:00
@@ -177,6 +177,8 @@
#define readl_relaxed(addr) readl(addr)
#define readq_relaxed(addr) readq(addr)

+#define mmiowb()
+
extern void __memcpy_fromio(unsigned long dest, unsigned long src, int count);
extern void __memcpy_toio(unsigned long dest, unsigned long src, int count);
extern void __memset_io(unsigned long dest, char fill, int count);
diff -Nru a/include/asm-ppc/io.h b/include/asm-ppc/io.h
--- a/include/asm-ppc/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ppc/io.h 2004-09-29 15:51:10 -07:00
@@ -197,6 +197,8 @@
#define memcpy_fromio(a,b,c) memcpy((a),(void *)(b),(c))
#define memcpy_toio(a,b,c) memcpy((void *)(a),(b),(c))

+#define mmiowb() asm volatile ("eieio" ::: "memory")
+
/*
* Map in an area of physical address space, for accessing
* I/O devices etc.
diff -Nru a/include/asm-ppc64/io.h b/include/asm-ppc64/io.h
--- a/include/asm-ppc64/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-ppc64/io.h 2004-09-29 15:51:10 -07:00
@@ -152,6 +152,8 @@
extern void _insl_ns(volatile u32 *port, void *buf, int nl);
extern void _outsl_ns(volatile u32 *port, const void *buf, int nl);

+#define mmiowb() asm volatile ("eieio" ::: "memory")
+
/*
* output pause versions need a delay at least for the
* w83c105 ide controller in a p610.
diff -Nru a/include/asm-s390/io.h b/include/asm-s390/io.h
--- a/include/asm-s390/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-s390/io.h 2004-09-29 15:51:10 -07:00
@@ -105,6 +105,8 @@
#define outb(x,addr) ((void) writeb(x,addr))
#define outb_p(x,addr) outb(x,addr)

+#define mmiowb()
+
#endif /* __KERNEL__ */

#endif
diff -Nru a/include/asm-sh/io.h b/include/asm-sh/io.h
--- a/include/asm-sh/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-sh/io.h 2004-09-29 15:51:10 -07:00
@@ -134,6 +134,8 @@
#define readw_relaxed(a) readw(a)
#define readl_relaxed(a) readl(a)

+#define mmiowb()
+
/*
* If the platform has PC-like I/O, this function converts the offset into
* an address.
diff -Nru a/include/asm-sh64/io.h b/include/asm-sh64/io.h
--- a/include/asm-sh64/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-sh64/io.h 2004-09-29 15:51:10 -07:00
@@ -86,6 +86,9 @@
#define readb(addr) sh64_in8(addr)
#define readw(addr) sh64_in16(addr)
#define readl(addr) sh64_in32(addr)
+#define readb_relaxed(addr) sh64_in8(addr)
+#define readw_relaxed(addr) sh64_in16(addr)
+#define readl_relaxed(addr) sh64_in32(addr)

#define writeb(b, addr) sh64_out8(b, addr)
#define writew(b, addr) sh64_out16(b, addr)
@@ -105,6 +108,8 @@
void outb(unsigned long value, unsigned long port);
void outw(unsigned long value, unsigned long port);
void outl(unsigned long value, unsigned long port);
+
+#define mmiowb()

#ifdef __KERNEL__

diff -Nru a/include/asm-sparc/io.h b/include/asm-sparc/io.h
--- a/include/asm-sparc/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-sparc/io.h 2004-09-29 15:51:10 -07:00
@@ -23,6 +23,8 @@
return ((w&0xff) << 8) | ((w>>8)&0xff);
}

+#define mmiowb()
+
/*
* Memory mapped I/O to PCI
*
diff -Nru a/include/asm-sparc64/io.h b/include/asm-sparc64/io.h
--- a/include/asm-sparc64/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-sparc64/io.h 2004-09-29 15:51:10 -07:00
@@ -439,6 +439,8 @@
return retval;
}

+#define mmiowb()
+
#ifdef __KERNEL__

/* On sparc64 we have the whole physical IO address space accessible
diff -Nru a/include/asm-v850/io.h b/include/asm-v850/io.h
--- a/include/asm-v850/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-v850/io.h 2004-09-29 15:51:10 -07:00
@@ -102,6 +102,8 @@
#define ioremap_writethrough(physaddr, size) (physaddr)
#define ioremap_fullcache(physaddr, size) (physaddr)

+#define mmiowb()
+
#define page_to_phys(page) ((page - mem_map) << PAGE_SHIFT)
#if 0
/* This is really stupid; don't define it. */
diff -Nru a/include/asm-x86_64/io.h b/include/asm-x86_64/io.h
--- a/include/asm-x86_64/io.h 2004-09-29 15:51:10 -07:00
+++ b/include/asm-x86_64/io.h 2004-09-29 15:51:10 -07:00
@@ -186,6 +186,8 @@
#define __raw_readl readl
#define __raw_readq readq

+#define mmiowb()
+
#ifdef CONFIG_UNORDERED_IO
static inline void __writel(u32 val, void *addr)
{

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