On Mon, May 14, 2018 at 04:55:26PM +0800, Baolin Wang wrote: > Hi, > > We will meet below issues when compensating the suspend time for the timekeeping. > > 1. We have too many different ways of dealing with persistent timekeeping > across architectures, so it is hard for one driver to compatable with different > architectures. > > 2. On some platforms (such as Spreadtrum platform), we registered the high > resolution timer as one clocksource to update the OS time, but the high > resolution timer will be stopped in suspend state. So we use another one > always-on timer (but low resolution) to calculate the suspend time to > compensate the OS time. Though we can register the always-on timer as one > clocksource, we need re-calculate the mult/shift with one larger conversion > range to calculate the suspend time and need update the clock in case of > running over the always-on timer. > > More duplicate code will be added if other platforms meet this case. > > 3. Now we have 3 sources that could be used to compensate the OS time: > Nonstop clocksource during suspend, persistent clock and rtc device, > which is complicated. Another hand is that the nonstop clocksource can > risk wrapping if the suspend time is too long, so we need one mechanism > to wake up the system before the nonstop clocksource wrapping. > > According to above issues, we can introduce one common persistent clock > framework to compatable with different architectures, in future we will > remove the persistent clock implementation for each architecture. Also > this framework will implement common code to help drivers to register easily. > Moreover if we converted all SUSPEND_NONSTOP clocksource to register to > be one persistent clock, we can remove the SUSPEND_NONSTOP clocksource > accounting in timekeeping, which means we can only compensate the OS time > from persistent clock and RTC. > > Will be appreciated for any comments. Thank you all. Why do we need another API ? Why not remove the present persistent API and rely on the SUSPEND_NONSTOP flag to do the right action at suspend and resume? We register different clocksources, the rating does the selection. When entering 'suspend', we check against the SUSPEND_NONSTOP flag and switch to the first clocksource with the best rating and the flag set. When resuming, we switch back to the highest rating. Having a clocksource out of the always-on domain must be notified with a trace in the log because this is not a normal situation. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
