Linux/AM4378: PRCM_PRM_RSTST AM437x - readout not making sense

Robert Woerle

Part Number: AM4378
Other Parts Discussed in Thread: AM4372, AM5728

Tool/software: Linux

Dear e2e

We are investigating a "system is resetting" issue and i wanted to read out the PRCM_PRM_RSTST for that to determine what the cpu knows about it.

Am i correc that PRCM_PRM_RSTST should be reachable via devmem2 under 0x44DF0004 ?

So i was testing to read the register under 3 scenarios ( cold boot, warm reboot, omap_watchdog) but i always get this result:

root@am437x-evm:~# devmem2 0x44DF0004
/dev/mem opened.
Memory mapped at address 0xb6f52000.
Read at address 0x44DF0004 (0xb6f52004): 0x00000500

Can you please give me a hint on how to get to the real PRCM_PRM_RSTST so i can at least get the info if it was warm, cold or a watchdog reason to boot ?

Regards Robert

over 7 years ago

0 Yordan Kovachev over 7 years ago

TI__Guru**** 161600 points

Hi,

It should be possible to access this register with devmem2. Which Processor SDK Linux version are you using, so I can try this on my side?

Best Regards,
Yordan

0 Robert Woerle over 7 years ago in reply to Yordan Kovachev

Intellectual 380 points

I basicly use SDK 3.0 with linux 4.1.18 or 4.4.x
i hope those dont make a difference here ?

0 Yordan Kovachev over 7 years ago in reply to Robert Woerle

TI__Guru**** 161600 points

Hi,

Sorry for the delay. I couldn't get my hands on AM4372 EVM, but I tested on AM5728 (IDK) which has the same functionality. I read the PRM_RSTST, which is supposed to log the global reset sources. I read the register after pressing the Warm Reset & Hard Reset buttons on the board, every time the register value is the same:
root@am57xx-evm:~# devmem2 0x4AE07D04
/dev/mem opened.
Memory mapped at address 0xb6f0b000.
Read at address 0x4AE07D04 (0xb6f0bd04): 0x00000001

What I can suggest is try to read the register from kernel space, doing __raw_readl() on 0x44DF0004.

Best Regards,
Yordan

0 Robert Woerle over 7 years ago in reply to Yordan Kovachev

Intellectual 380 points

So ur saying on your am5728 it is also not working . hmmm. well then i will try to find some time to printk bomb my kernel with your suggested __raw_readl() to get a idea if that register is ever acurate during the boot ( maybe something in the kernel resets it ? maybe even u-boot ?? )

0 Yordan Kovachev over 7 years ago in reply to Robert Woerle

TI__Guru**** 161600 points

I don't think u-boot touches these registers. So try modifying the kernel code.

Best Regards,
Yordan

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Linux/AM4378: PRCM_PRM_RSTST AM437x - readout not making sense