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SubjectRe: [PATCH v3 0/8] NVIDIA Tegra clocksource driver improvements
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03.06.2019 10:17, Peter De Schrijver пишет:
> On Fri, May 31, 2019 at 03:33:41PM +0300, Dmitry Osipenko wrote:
>> 31.05.2019 11:26, Peter De Schrijver пишет:
>>> On Fri, May 24, 2019 at 06:32:45PM +0300, Dmitry Osipenko wrote:
>>>> Hello,
>>>>
>>>> This series primarily unifies the driver code across all Tegra SoC
>>>> generations. In a result the clocksources are allocated per-CPU on
>>>> older Tegra's and have a higher rating than the arch-timer, the newer
>>>> Tegra210 is getting support for microsecond clocksource and the driver's
>>>> code is getting much cleaner. Note that arch-timer usage is discouraged on
>>>> all Tegra's due to the time jitter caused by the CPU frequency scaling.
>>>
>>> I think the limitations are more as follows:
>>>
>>> Chip timer suffers cpu dvfs jitter can wakeup from cc7
>>> T20 us-timer No Yes
>>> T20 twd timer Yes No?
>>> T30 us-timer No Yes
>>> T30 twd timer Yes No?
>>> T114 us-timer No Yes
>>> T114 arch timer No Yes
>>> T124 us-timer No Yes
>>> T124 arch timer No Yes
>>> T210 us-timer No Yes
>>> T210 arch timer No No
>>> T210 clk_m timer No Yes
>>>
>>> right?
>>
>> Doesn't arch timer run off the CPU clock? If yes (that's what I
>> assumed), then it should be affected by the DVFS. Otherwise I'll lower
>> the clocksource's rating for T114/124/132.
>>
>
> No. It doesn't. This is the big change between A9 and later CPUs.

Thank you for the clarification, I'll add a patch to lower the rating
where appropriate.

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