diff options
| author | cinap_lenrek <cinap_lenrek@felloff.net> | 2022-07-09 16:06:42 +0000 |
|---|---|---|
| committer | cinap_lenrek <cinap_lenrek@felloff.net> | 2022-07-09 16:06:42 +0000 |
| commit | 90f47fadf8808d84d9bde8316f3945e60650093d (patch) | |
| tree | e7700de37f4f3a1b67f1621a422b5e7a032457bf /sys/src/9/imx8/clock.c | |
| parent | 2b89cdee025d9b3faccd62bc3515d7ed749ae26f (diff) | |
imx8: detect cpu lcycles() frequency
Diffstat (limited to 'sys/src/9/imx8/clock.c')
| -rw-r--r-- | sys/src/9/imx8/clock.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/sys/src/9/imx8/clock.c b/sys/src/9/imx8/clock.c index a6b9ab034..19bbc9625 100644 --- a/sys/src/9/imx8/clock.c +++ b/sys/src/9/imx8/clock.c @@ -29,6 +29,9 @@ localclockintr(Ureg *ureg, void *) void clockinit(void) { + uvlong tstart, tend; + ulong t0, t1; + syswr(PMCR_EL0, 1<<6 | 7); syswr(PMCNTENSET, 1<<31); syswr(PMUSERENR_EL0, 1<<2); @@ -41,8 +44,22 @@ clockinit(void) freq = sysrd(CNTFRQ_EL0); print("timer frequency %lld Hz\n", freq); } - m->cpuhz = freq; - m->cpumhz = (freq + Mhz/2 - 1) / Mhz; + tstart = sysrd(CNTPCT_EL0); + do{ + t0 = lcycles(); + }while(sysrd(CNTPCT_EL0) == tstart); + tend = tstart + (freq/100); + do{ + t1 = lcycles(); + }while(sysrd(CNTPCT_EL0) < tend); + t1 -= t0; + m->cpuhz = 100 * t1; + m->cpumhz = (m->cpuhz + Mhz/2 - 1) / Mhz; + + /* + * we are using virtual counter register CNTVCT_EL0 + * instead of the performance counter in userspace. + */ m->cyclefreq = freq; intrenable(IRQcntpns, localclockintr, nil, BUSUNKNOWN, "clock"); |