Re: [Qemu-devel] arm mptimer implementation - why prescaler is multiply by 10?

[Dmitry Osipenko <digetx@gmail.com>]

27.10.2015 16:48, Krzeminski, Marcin (Nokia - PL/Wroclaw) пишет:
> Hello,
> I am playing with U-Boot on ARM under qemu.
> U-boot uses mptimer, and under qemu one second takes about 1 in real world.
> At the moment it seem that in u-boot is ok, so I have question about below function.
> Why prescaler value is multiply by 10?
> static inline uint64_t a9_gtimer_get_conv(A9GTimerState *s)
> {
>      uint64_t prescale = extract32(s->control, R_CONTROL_PRESCALER_SHIFT,
>                                    R_CONTROL_PRESCALER_LEN);
>      return (prescale + 1) * 10;
> }
> Regards,
> Marcin

Hello Marcin,

 From my observation, Linux kernel is booting noticeably faster in the emulated 
guest and host machine CPU usage is lower if we "artificially" slowdown the 
MPtimer. You really shouldn't use it for the RTC, so doing that trick shouldn't 
affect guest behavior.

However, maybe there is some other rational behind it and Peter C and/or Peter M 
might know better.

-- 
Dmitry