seL4/Genode on zynq7000; TTC Timer Component
schlatow at ida.ing.tu-bs.de
Fri Nov 1 10:12:22 CET 2019
> I'd assume that seL4 uses the GTC or the cpu private timer(s)?
> I must admit, that I didn't look into them - I just used the existing
> imx6 and imx7 targets for comparison. And although both do also have
> cpu private timer(s), they use different timers (epit and gpt) in the
> case of seL4/Genode. Therefore I was under the impression, that a
> dedicated (multi-purpose) timer is necessary.
I had a brief look at the sel4 source code. in src/plat/zynq7000 there are two dts files which suggest that the standard version uses the private timer whereas the mcs version uses the GTC.
> My tickrate should therefore be: 108.000 ticks/ms or when using a
> prescaler value of 2^6=128 => ~1688 ticks/ms Since the prescaler
> register uses the following formula count/2^(N+1), I set it to 0x5.
2^6 is actually 64 so maybe this explains why the timer is off by factor 2.
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