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. Sincerely TonyWWang-oc
