Messages in this thread | | | Date | Wed, 24 Aug 2005 14:43:48 +0200 (CEST) | From | moreau francis <> | Subject | question on memory barrier |
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Hi,
I'm currently trying to write a USB driver for Linux. The device must be configured by writing some values into the same register but I want to be sure that the writing order is respected by either the compiler and the cpu.
For example, here is a bit of driver's code:
""" #include <asm/io.h>
static inline void dev_out(u32 *reg, u32 value) { writel(value, regs); }
void config_dev(void) { dev_out(reg_a, 0x0); /* first io */ dev_out(reg_a, 0xA); /* second io */ }
void config_dev_fixed(void) { dev_out(reg_a, 0x0); /* first io */ wmb(); dev_out(reg_a, 0xA); /* second io */ wmb(); } """
In this case, am I sure that the order will be respected ? can gcc remove the first io while optimizing...If so, does "config_dev_fixed" fix it ?
thanks for your answers,
Francis
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