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SRC_GPR1 (0x020D8020) usage question (iMX6)

Question asked by Łukasz Majewski on Feb 9, 2018
Latest reply on Feb 12, 2018 by Łukasz Majewski

Dear All,

 

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.

 

My questions:

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,

Łukasz Majewski

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