I'm a bit puzzled with the purpose of SRC_GPRx registers on iMX6Q SoC.
According to the iMX6Q Applications Processor Reference Manual (IMX6DQRM.pdf rev.4):
Chapter 60.7.7 (page 5088), there is a NOTE:
"This register is used by the ROM code and should not be used
by application software."
Could somebody explain what are the restrictions of using those registers? (SRC_GPRx)
What I've understood from the above manual:
Those registers keep their content during reset, so can be used as a storage of the boot count (from u-boot bootloader).
However, those may be as well overwritten with resume address and arguments when we go into deep power down mode(s).
Similar question has been posed in:iMX6 persistent data storage , but with no reply.
1. Is it possible to reuse those registers in user application, which requires preserving data over (WDT, soft) reset?
2. Are there any other recommended registers for such purpose?
I've found SNVS_LPGPR (0x020CC068) - Chapter 57.9.14, which can be used in user application, but is recommended for retaining data in low-power mode(s).
Thread with SNVS_LPGPR usage example: How to Support Recovery Mode for POR Reboot Based on i.MX6 Android R13.4.1
Thanks in advance for help,