From: Lennert Buytenhek Date: Sat, 29 Oct 2005 15:28:28 +0000 (+0100) Subject: [ARM] 3053/1: introduce ixp2000_reg_wrb (ixp2000_reg_write plus readback) X-Git-Tag: v2.6.15-rc1~731^2^2~4 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b4a1f67fbfb848ded8cf0c6c305224534144ab2d;p=linux-2.6 [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 Signed-off-by: Deepak Saxena Signed-off-by: Russell King --- diff --git a/include/asm-arm/arch-ixp2000/platform.h b/include/asm-arm/arch-ixp2000/platform.h index 6e5b6a955a..a66317ab20 100644 --- a/include/asm-arm/arch-ixp2000/platform.h +++ b/include/asm-arm/arch-ixp2000/platform.h @@ -25,6 +25,31 @@ static inline void ixp2000_reg_write(volatile void *reg, unsigned long val) *((volatile unsigned long *)reg) = 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