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authorLennert Buytenhek <buytenh@wantstofly.org>2005-10-29 11:28:28 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2005-10-29 11:28:28 -0400
commitb4a1f67fbfb848ded8cf0c6c305224534144ab2d (patch)
tree58988f4a66886659518e971fdc2445ecb9e81ecf /include/asm-arm
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')
-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 6e5b6a955abe..a66317ab2071 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)
26} 26}
27 27
28/* 28/*
29 * On the IXP2400, we can't use XCB=000 due to chip bugs. We use
30 * XCB=101 instead, but that makes all I/O accesses bufferable. This
31 * is not a problem in general, but we do have to be slightly more
32 * careful because I/O writes are no longer automatically flushed out
33 * of the write buffer.
34 *
35 * In cases where we want to make sure that a write has been flushed
36 * out of the write buffer before we proceed, for example when masking
37 * a device interrupt before re-enabling IRQs in CPSR, we can use this
38 * function, ixp2000_reg_wrb, which performs a write, a readback, and
39 * issues a dummy instruction dependent on the value of the readback
40 * (mov rX, rX) to make sure that the readback has completed before we
41 * continue.
42 */
43static inline void ixp2000_reg_wrb(volatile void *reg, unsigned long val)
44{
45 unsigned long dummy;
46
47 *((volatile unsigned long *)reg) = val;
48
49 dummy = *((volatile unsigned long *)reg);
50 __asm__ __volatile__("mov %0, %0" : "+r" (dummy));
51}
52
53/*
29 * Boards may multiplex different devices on the 2nd channel of 54 * Boards may multiplex different devices on the 2nd channel of
30 * the slowport interface that each need different configuration 55 * the slowport interface that each need different configuration
31 * settings. For example, the IXDP2400 uses channel 2 on the interface 56 * settings. For example, the IXDP2400 uses channel 2 on the interface