On Tue, 20 Nov 2018, Linus Walleij wrote:
Yes you already see the same as I see: this chip MK68901 has no less than four timers. I bet the kernel is just using one of them, out of habit. By just setting another timer as free-running we get a classic and clean Linux clocksource for the Atari.
These are all 8-bit timers. Whereas the smallest clocksource mask I can find with grep is 24-bits. You can divide the oscillator down to 12288 Hz giving a maximum period of 20 ms. My concern would be that clocksource counter wrap could still go undetected given a little interrupt latency.
This is however a very good start in untangling the mess (as is the whole patch series).
It should be exciting to see what happens when some of these changes get tested 8-) I've only seen results for Mac and Atari so far.
As with the Amiga, this chip also has an RTC clock that should go to the RTC subsystem, naturally.
I think some Atari's have an MC146818, which is drivers/rtc/rtc-cmos.c, arch/alpha/kernel/rtc.c etc. --
Yours, Linus Walleij
