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SubjectRe: [PATCH v3 0/6] clocksource: rework Atmel TCB timer driver
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On 28/03/2018 16:16, Alexandre Belloni wrote:
> On 28/03/2018 at 15:03:11 +0200, Daniel Lezcano wrote:
>> On 28/03/2018 12:29, Alexander Dahl wrote:
>>> Hello Daniel,
>>>
>>> Am Dienstag, 27. März 2018, 13:30:22 CEST schrieb Daniel Lezcano:
>>>> Can you can give a rough amount for the irq rate on the timer ?
>>>
>>> I used itop [1] now to get a rough estimate. First with kernel v4.14.29-rt25
>>> (fully preempt RT):
>>>
>>> INT NAME RATE MAX
>>> 19 [ vel tc_clkevt] 397 Ints/s (max: 432)
>>> 26 [ vel eth0] 4 Ints/s (max: 38)
>>>
>>> Next test with kernel v4.15.13 gives (slightly slower, but non-RT):
>>>
>>> INT NAME RATE MAX
>>> 19 [ vel tc_clkevt] 248 Ints/s (max: 273)
>>> 26 [ vel eth0] 4 Ints/s (max: 11)
>>>
>>> With kernel v4.16-rc7 plus this patch series and tcb as clocksource:
>>>
>>> INT NAME RATE MAX
>>> 17 [vel timer@fffa] 2164 Ints/s (max: 2183)
>>> 26 [ vel eth0] 5 Ints/s (max: 10)
>>>
>>> Is this the information you wanted? If not, could you point me on how to get
>>> the requested irq rate?
>>
>> It is perfect. Thanks!
>>
>> It confirms what I was worried about: the clocksource wraps up too
>> quickly thus raising an interrupt every 400us. That is why I asked
>> Alexande about a prescalar register.
>>
>
> The code should behave exactly the same between the previous and the new
> driver. The interrupt is not coming from the clocksource but from the
> clockevent and it is already on the slowest clock, the 32kHz one.

Do you have an explanation of why the rate is much higher ?


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