diff options
Diffstat (limited to 'src/northbridge')
| -rw-r--r-- | src/northbridge/intel/sandybridge/udelay.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/src/northbridge/intel/sandybridge/udelay.c b/src/northbridge/intel/sandybridge/udelay.c index 3d8ba96d75..6ceea40940 100644 --- a/src/northbridge/intel/sandybridge/udelay.c +++ b/src/northbridge/intel/sandybridge/udelay.c @@ -23,9 +23,22 @@ #include <cpu/x86/msr.h> /** - * Intel Core(tm) cpus always run the TSC at the maximum possible CPU clock + * Intel SandyBridge/IvyBridge CPUs always run the TSC at BCLK=100MHz */ +/* Simple 32- to 64-bit multiplication. Uses 16-bit words to avoid overflow. + * This code is used to prevent use of libgcc's umoddi3. + */ +static inline void multiply_to_tsc(tsc_t *const tsc, const u32 a, const u32 b) +{ + tsc->lo = (a & 0xffff) * (b & 0xffff); + tsc->hi = ((tsc->lo >> 16) + + ((a & 0xffff) * (b >> 16)) + + ((b & 0xffff) * (a >> 16))); + tsc->lo = ((tsc->hi & 0xffff) << 16) | (tsc->lo & 0xffff); + tsc->hi = ((a >> 16) * (b >> 16)) + (tsc->hi >> 16); +} + void udelay(u32 us) { u32 dword; @@ -33,15 +46,12 @@ void udelay(u32 us) msr_t msr; u32 fsb = 100, divisor; u32 d; /* ticks per us */ - u32 dn = 0x1000000 / 2; /* how many us before we need to use hi */ msr = rdmsr(0xce); divisor = (msr.lo >> 8) & 0xff; - d = fsb * divisor; - - tscd.hi = us / dn; - tscd.lo = (us - tscd.hi * dn) * d; + d = fsb * divisor; /* On Core/Core2 this is divided by 4 */ + multiply_to_tsc(&tscd, us, d); tsc1 = rdtsc(); dword = tsc1.lo + tscd.lo; |