1 files changed, 25 insertions, 25 deletions

diff --git a/include/asm-arm/arch-ixp2000/platform.h b/include/asm-arm/arch-ixp2000/platform.h
index abdcf51bd283..a66317ab2071 100644
--- a/include/asm-arm/arch-ixp2000/platform.h
+++ b/include/asm-arm/arch-ixp2000/platform.h
@@ -15,40 +15,40 @@
 
 #ifndef __ASSEMBLY__
 
+static inline unsigned long ixp2000_reg_read(volatile void *reg)
+{
+        return *((volatile unsigned long *)reg);
+}
+
+static inline void ixp2000_reg_write(volatile void *reg, unsigned long val)
+{
+        *((volatile unsigned long *)reg) = val;
+}
+
 /*
- * The IXP2400 B0 silicon contains an erratum (#66) that causes writes
- * to on-chip I/O register to not complete fully. What this means is
- * that if you have a write to on-chip I/O followed by a back-to-back
- * read or write, the first write will happen twice. OR...if it's
- * not a back-to-back transaction, the read or write will generate
- * incorrect data.
- *
- * The official work around for this is to set the on-chip I/O regions
- * as XCB=101 and then force a read-back from the register.
+ * On the IXP2400, we can't use XCB=000 due to chip bugs.  We use
+ * XCB=101 instead, but that makes all I/O accesses bufferable.  This
+ * is not a problem in general, but we do have to be slightly more
+ * careful because I/O writes are no longer automatically flushed out
+ * of the write buffer.
  *
+ * In cases where we want to make sure that a write has been flushed
+ * out of the write buffer before we proceed, for example when masking
+ * a device interrupt before re-enabling IRQs in CPSR, we can use this
+ * function, ixp2000_reg_wrb, which performs a write, a readback, and
+ * issues a dummy instruction dependent on the value of the readback
+ * (mov rX, rX) to make sure that the readback has completed before we
+ * continue.
  */
-#if defined(CONFIG_ARCH_ENP2611) || defined(CONFIG_ARCH_IXDP2400) || defined(CONFIG_ARCH_IXDP2401)
-
-#include <asm/system.h>         /* Pickup local_irq_ functions */
-
-static inline void ixp2000_reg_write(volatile void *reg, unsigned long val)
+static inline void ixp2000_reg_wrb(volatile void *reg, unsigned long val)
 {
         unsigned long dummy;
-        unsigned long flags;
 
-        local_irq_save(flags);
         *((volatile unsigned long *)reg) = val;
-        barrier();
+
         dummy = *((volatile unsigned long *)reg);
-        local_irq_restore(flags);
-}
-#else
-static inline void ixp2000_reg_write(volatile void *reg, unsigned long val)
-{
-        *((volatile unsigned long *)reg) = val;
+        __asm__ __volatile__("mov %0, %0" : "+r" (dummy));
 }
-#endif  /* IXDP2400 || IXDP2401 */
-#define ixp2000_reg_read(reg)   (*((volatile unsigned long *)reg))
 
 /*
  * Boards may multiplex different devices on the 2nd channel of