According to this thread: https://community.nxp.com/thread/456977 the LP RTC does not exist in the i.MX6ULL.
Well, I observed that in the datasheet the registers LPSRTCMR (offset 0x50) and LPSRTCLR (offset 0x54) indeed are not present/documented (they are documented in the i.MX6UL).
This thread also mentions the use of the RTC for the ULL, but not that it doesn't exist: https://community.nxp.com/thread/481779
But now the fun part: If I readout those registers they seem to work, also the rtc-snvs driver looks to be working.
So it seems the LP RTC is present in the ULL (at least the one I have: MCIMX6Y2CVM08AA =industrial 792 MHz).
What I also saw is that the imx6ull.dtsi still contains the section "snvs-rtc-lp".
I would expect that it would have been removed when this RTC is absent?
So why was that not removed from the dtsi if its absent? (We use the linux-imx_4.1.15 branch)
So my questions:
- Why is this working?
- Is it a documentation error and the LP RTC is available as intended?
- Is is a chip design issue that it was forgotten to remove the functionality of from the chip itself?
- Is there a plan to remove the LP RTC from the chip in a future version?
It all boils down to the question: When I start using the LP RTC how big is the risk that in a newer production batch the LP RTC will "vanish"?
Note: Since probably nobody is going to read a closed/answered thread (456977) I opened this new question on this subject. I will refer to this question in the other thread and remove it there.
And by the way: There is no Category for i.MX6ULL, only the i.MX6UL to select for posting questions!