Messages in this thread | | | Subject | Re: [PATCH v8 4/6] clocksource: stm32: only use 32 bits timers | From | Daniel Lezcano <> | Date | Fri, 8 Dec 2017 08:52:12 +0100 |
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On 07/12/2017 21:36, Benjamin Gaignard wrote: > 2017-12-07 17:49 GMT+01:00 Daniel Lezcano <daniel.lezcano@linaro.org>: >> On 07/12/2017 17:33, Benjamin Gaignard wrote: >>> 2017-12-07 16:27 GMT+01:00 Daniel Lezcano <daniel.lezcano@linaro.org>: >>>> On 14/11/2017 09:52, Benjamin Gaignard wrote: >>>>> The clock driving counters is at 90MHz so the maximum period >>>>> for 16 bis counters is around 750 ms which is a short period >>>>> for a clocksource. >>>> >>>> Isn't it 728us ? >>> >>> yes it is: 2^16 / 90.000.000 => 728us >> >> Ok, now I can do the connection with the previous patch. >> >> So, the real issue of all this is the 16bits clocksource is wrapping up >> every 728us, hence the clockevent periodically expires every ~728us to >> keep the timekeeping consistent. Unfortunately, the kernel has a too >> high overhead for this as the system is consistently processing this >> timer leading to a CPU time resource starvation. >> >> Is that correct ? > > Yes that is correct
Oh man. That was unclear since the beginning, we are not talking about inaccurate clocksource or whatever but just these 16bits timers can't work on Linux.
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