Athlon/3DNow write prefetch?

Athlon/3DNow write prefetch?

[Andreas Franck]

Hello people,

in looking at the prefetch code from include/asm-i386/processor.h on 
2.4.9-ac9, I have noticed that prefetchw seems not to be implemented right:

The Athlon/3DNow prefetchw() implementation uses the `prefetch' assembler 
instruction, which is in fact a read prefetch, while it should use the 
`prefetchw' instruction, which is for write prefetch.

Any comments on this?

Greetings,
Andreas

(Here the excerpt from the code...)

[...]

/* Prefetch instructions for Pentium III and AMD Athlon */
#ifdef  CONFIG_MPENTIUMIII
 
#define ARCH_HAS_PREFETCH
extern inline void prefetch(const void *x)
{
        __asm__ __volatile__ ("prefetchnta (%0)" : : "r"(x));
}
 
#elif CONFIG_X86_USE_3DNOW
 
#define ARCH_HAS_PREFETCH
#define ARCH_HAS_PREFETCHW
#define ARCH_HAS_SPINLOCK_PREFETCH
 
extern inline void prefetch(const void *x)
{
         __asm__ __volatile__ ("prefetch (%0)" : : "r"(x));
}
 
extern inline void prefetchw(const void *x)
{
         __asm__ __volatile__ ("prefetch (%0)" : : "r"(x));
                                ^^^^^^^^ <- Shouldn't this be prefetchw ???
} 
#define spin_lock_prefetch(x)   prefetchw(x)
 
#endif

Re: Athlon/3DNow write prefetch?

[Alan Cox]

> The Athlon/3DNow prefetchw() implementation uses the `prefetch' assembler 
> instruction, which is in fact a read prefetch, while it should use the 
> `prefetchw' instruction, which is for write prefetch.

Yep