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. Peter. > 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.
