Re: [PATCH v3 0/8] NVIDIA Tegra clocksource driver improvements

From: Dmitry Osipenko
Date: Sat Jun 01 2019 - 09:05:36 EST

31.05.2019 23:31, Daniel Lezcano ÐÐÑÐÑ:
> On 31/05/2019 14:33, Dmitry Osipenko wrote:
>> 31.05.2019 11:26, Peter De Schrijver ÐÐÑÐÑ:
>>> 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.
>> TWD can't wake CPU from the power-down state, so it's a solid "No" for
>> TWD in the "can wakeup from cc7" column.
> Wouldn't make sense to rename the timer-tegra20.c to timer-tegra.c now ?

Wouldn't hurt, given the refreshment that driver is getting lately. I'll
include a patch for that in the next revision, thanks.