On 10.06.23 10:31, Alexandre Belloni wrote: > Hello Jan, > > On 09/06/2023 23:04:12+0200, Jan Kiszka wrote: >> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> >> The VL bit in the seconds register remains set only until seconds are >> written under main power. As this often happens during boot-up after >> picking up a network time, make sure to preserve the low battery state >> across this, caching it and returning it via the RTC_VL_BACKUP_LOW bit. >> >> To permit userspace clearing this state during runtime, also implement >> RTC_VL_CLR that works against the cached state. >> >> This is emulating RTCs which have a battery voltage check that works >> under main power as well. >> > > Emulating doesn't work well and I deliberately chose to not implement > it. For example, in your scenario, if you boot twice without using > VL_READ, you anyway have lost the information. This makes emulating > unreliabl. The fix you need is in userspace where you have to ensure you > read the status before setting the time. Then let's make sure the bit is also set in the hardware register. Then also the reboot issue (which is practically a minor one) is solved. The current situation is far from optimal. Jan -- Siemens AG, Technology Competence Center Embedded Linux
