> I have ported Linux 2.6 to PowerPC 440. Could you tell me
> how it is possible to access the timebase register (TBU, TBL)
> from user space (in Linux) because I want to measure the time
> of an application that runs in Linux?
I just grabbed this code from the kernel (you can put the macro
expansions into the function if you like):
typedef unsigned long long u64;
#define mftbl() ({unsigned long rval; \
asm volatile("mftbl %0" : "=r" (rval)); rval;})
#define mftbu() ({unsigned long rval; \
asm volatile("mftbu %0" : "=r" (rval)); rval;})
static inline u64 get_tb(void)
{
unsigned int tbhi, tblo, tbhi2;
do {
tbhi = get_tbu();
tblo = get_tbl();
tbhi2 = get_tbu();
} while (tbhi != tbhi2);
return ((u64)tbhi << 32) | tblo;
}
The timebase frequency is available in text form from
/proc/cpuinfo and in binary (as a 4-byte bigendian
integer)from /proc/device-tree/...
grep timebase /proc/cpuinfo
find /proc/device-tree -name timebase-frequency -print \
-exec od -td -An '{}' \;
Clive
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