Hello Roman, On Tue, Sep 29, 2020 at 02:13:47PM +0300, Roman Stratiienko wrote: > Fixes linux_kselftest:timers_inconsistency-check_arm_64 > > Test logs without the fix: > ''' > binary returned non-zero. Exit code: 1, stderr: , stdout: > Consistent CLOCK_REALTIME > 1601335525:467086804 > 1601335525:467087554 > 1601335525:467088345 > 1601335525:467089095 > 1601335525:467089887 > 1601335525:467090637 > 1601335525:467091429 > 1601335525:467092179 > 1601335525:467092929 > 1601335525:467093720 > 1601335525:467094470 > 1601335525:467095262 > 1601335525:467096012 > 1601335525:467096804 > -------------------- > 1601335525:467097554 > 1601335525:467077012 > -------------------- > 1601335525:467099095 > 1601335525:467099845 > 1601335525:467100637 > 1601335525:467101387 > 1601335525:467102179 > 1601335525:467102929 > '''
Can you reproduce the issue with a fixed CPU frequency. I suspect the root cause is around CPU frequency scaling code on A64, and timer jumps happen when the kernel is changing CPU frequency. I fixed a similar issue on H3 SoC just by changing the CPU frequency scaling code, without having to touch the timer readout code. https://megous.com/git/linux/commit/?h=ths-5.9&id=51ff1a6d80126f678efca42555f93efa611f50c4 regards, o. > Signed-off-by: Roman Stratiienko <r.stratiie...@gmail.com> > CC: linux-arm-ker...@lists.infradead.org > CC: linux-kernel@vger.kernel.org > CC: linux-su...@googlegroups.com > CC: meg...@megous.com > --- > drivers/clocksource/arm_arch_timer.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c > b/drivers/clocksource/arm_arch_timer.c > index 6c3e841801461..d50aa43cb654b 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -346,16 +346,17 @@ static u64 notrace arm64_858921_read_cntvct_el0(void) > * number of CPU cycles in 3 consecutive 24 MHz counter periods. > */ > #define __sun50i_a64_read_reg(reg) ({ > \ > - u64 _val; \ > + u64 _val1, _val2; \ > int _retries = 150; \ > \ > do { \ > - _val = read_sysreg(reg); \ > + _val1 = read_sysreg(reg); \ > + _val2 = read_sysreg(reg); \ > _retries--; \ > - } while (((_val + 1) & GENMASK(9, 0)) <= 1 && _retries); \ > + } while (((_val2 - _val1) > 0x10) && _retries); \ > \ > WARN_ON_ONCE(!_retries); \ > - _val; \ > + _val2; \ > }) > > static u64 notrace sun50i_a64_read_cntpct_el0(void) > -- > 2.25.1 >
