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authorLennert Buytenhek <buytenh@wantstofly.org>2005-10-29 16:28:28 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2005-10-29 16:28:28 +0100
commitb4a1f67fbfb848ded8cf0c6c305224534144ab2d (patch)
tree58988f4a66886659518e971fdc2445ecb9e81ecf /include/asm-arm/arch-ixp2000/platform.h
parentecbea7a2dae94092db9566bcd1f38535e9b3cde9 (diff)
[ARM] 3053/1: introduce ixp2000_reg_wrb (ixp2000_reg_write plus readback)
Patch from Lennert Buytenhek Introduce ixp2000_reg_wrb, which is a variant of ixp2000_reg_write that does a readback from the target register, to make sure that the write has been flushed out of the write buffer. Unlike the previous (ineffective) readback in ixp2000_reg_write, this readback is followed by an instruction that depends on the value of the readback so that the CPU actually stalls until the readback has completed. Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org> Signed-off-by: Deepak Saxena <dsaxena@plexity.net> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'include/asm-arm/arch-ixp2000/platform.h')
-rw-r--r--include/asm-arm/arch-ixp2000/platform.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/include/asm-arm/arch-ixp2000/platform.h b/include/asm-arm/arch-ixp2000/platform.h
index 6e5b6a955ab..a66317ab207 100644
--- a/include/asm-arm/arch-ixp2000/platform.h
+++ b/include/asm-arm/arch-ixp2000/platform.h
@@ -26,6 +26,31 @@ static inline void ixp2000_reg_write(volatile void *reg, unsigned long val)
}
/*
+ * 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.
+ */
+static inline void ixp2000_reg_wrb(volatile void *reg, unsigned long val)
+{
+ unsigned long dummy;
+
+ *((volatile unsigned long *)reg) = val;
+
+ dummy = *((volatile unsigned long *)reg);
+ __asm__ __volatile__("mov %0, %0" : "+r" (dummy));
+}
+
+/*
* Boards may multiplex different devices on the 2nd channel of
* the slowport interface that each need different configuration
* settings. For example, the IXDP2400 uses channel 2 on the interface