diff options
Diffstat (limited to 'sys/src/9/bcm64/clock.c')
| -rw-r--r-- | sys/src/9/bcm64/clock.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/sys/src/9/bcm64/clock.c b/sys/src/9/bcm64/clock.c index f7b3e55f7..f5fcc4784 100644 --- a/sys/src/9/bcm64/clock.c +++ b/sys/src/9/bcm64/clock.c @@ -2,14 +2,14 @@ * bcm283[56] timers * System timers run at 1MHz (timers 1 and 2 are used by GPU) * ARM timer usually runs at 250MHz (may be slower in low power modes) - * Cycle counter runs at 700MHz (unless overclocked) * All are free-running up-counters * * Use system timer 3 (64 bits) for hzclock interrupts and fastticks * For smp on bcm2836, use local generic timer for interrupts on cpu1-3 * Use ARM timer (32 bits) for perfticks * Use ARM timer to force immediate interrupt - * Use cycle counter for cycles() + * Use performance cycle counter for lcycles() + * Use generic timer virtual counter for cycles() */ #include "u.h" @@ -118,6 +118,7 @@ clockinit(void) syswr(PMCR_EL0, 1<<6 | 7); syswr(PMCNTENSET, 1<<31); syswr(PMUSERENR_EL0, 1<<2); + syswr(CNTKCTL_EL1, 1<<1); syswr(CNTP_TVAL_EL0, ~0UL); if(m->machno == 0){ @@ -147,7 +148,19 @@ clockinit(void) t1 -= t0; m->cpuhz = 100 * t1; m->cpumhz = (m->cpuhz + Mhz/2 - 1) / Mhz; - m->cyclefreq = m->cpuhz; + + /* + * Cyclefreq used to be the same as cpuhz as + * we where using the PMCCNTR_EL0 which counts + * per core cpu cycles. But is is kind of useless + * in userspace because each core has a differnet + * counter and it stops when the core is idle (WFI). + * So we change it to use the generic timer + * virtual counter register CNTVCT_EL0 instead + * running at the same frequency as system timer. + * (CNTFRQ_EL0 is WRONG on raspberry pi). + */ + m->cyclefreq = SystimerFreq; if(m->machno == 0){ tn->cs = 1<<3; |