On August 17, 2021 9:21:03 PM GMT+08:00, Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx> wrote: >On 17/08/2021 19:09:28+0800, tonywwang-oc@xxxxxxxxxxx wrote: >> >> >> On August 16, 2021 8:36:48 PM GMT+08:00, Alexandre Belloni ><alexandre.belloni@xxxxxxxxxxx> wrote: >> >On 16/08/2021 18:03:13+0800, Tony W Wang-oc wrote: >> >> >> >> On 16/08/2021 16:24, Alexandre Belloni wrote: >> >> > Hello, >> >> > >> >> > On 16/08/2021 21:47:18+0800, Tony W Wang-oc wrote: >> >> >> When the RTC divider is changed from reset to an operating time >> >base, >> >> >> the first update cycle should be 500ms later. But on some >Zhaoxin >> >SOCs, >> >> >> this first update cycle is one second later. >> >> >> >> >> >> So set RTC time on these Zhaoxin SOCs will causing 500ms delay. >> >> >> >> >> > >> >> > Can you explain what is the relationship between writing the >> >divider and >> >> > the 500ms delay? >> >> >> Isn't the issue that you are using systohc and set_offset_nsec >is >> >set to >> >> > NSEC_PER_SEC / 2 ? >> >> > >> >> No. >> >> When using #hwclock -s to set RTC time and set_offset_nsec is >> >> NSEC_PER_SEC / 2, the function mc146818_set_time() requires the >first >> >> update cycle after RTC divider be changed from reset to an >operating >> >> mode is 500ms as the MC146818A spec specified. But on some Zhaoxin >> >SOCs, >> >> the first update cycle of RTC is one second later after RTC >divider >> >be >> >> changed from reset to an operating mode. So the first update cycle >> >after >> >> RTC divider be changed from reset to an operation mode on These >SOCs >> >> will causing 500ms delay with current mc146818_set_time() >> >implementation. >> >> >> > >> >What happens with hwclock --delay=0 -s ? >> >> With "hwclock --delay=0 -s" still have this problem. Actually, this >500ms delay caused by writing the RTC time on these Zhaoxin SOCs. >> As I've tested, with hwclock --delay=0 -w can fix it too. >> > >Both -s and -w end up calling set_hardware_clock_exact() so both should >end up with the correct time. If this is not the case, then hwclock >needs to be fixed. I checked Util-linux-2.37.2, hwclock -w will call set_hardware_clock_exact() and hwclock -s will not. Please correct me if I'm wrong. Sincerely TonyWWang-oc
