i.MX7D Watchdog reset status register, WDOG1_WRSR always report POR when wdog times out and resets the board.

[SharmaS]

Hi,

We have a custom board based using i.MX7D (MCIMX7D3DVK10SC). Our BSP is based on NXP kernel release imx_4.9.11_1.0.0_ga and boot loader release uboot-imx rel_imx_4.9.x_1.0.0_ga.

I am using and/or configuring WDOG1 similar to that of SABRE board.  When the board boots, I do "echo 1 > /dev/watchdog0" to start the watchdog and then do not reset timeout (starve the wdog). This leads to board reset and reboot the system. I then break into u-boot and do "md.w 0x3028004 1" to read WDOG_WRSR from uboot. It reports 0010 that maps to POR. It doesn't map to TOUT (wdog timeout). Also, I added printk statements in watchdog driver to print bootstatus from kernel. This too reports 0010 (POR).

The same behavior is observed with SABRE board as well.

Any help to get this resolved is appreciated.

#imx7d‌ #watchdog‌ #wdog‌

[igorpadykov · Accepted solution]

Hi Swetang

seems behaviour is expected as wdog on i.MX7D Sabre schematic shortly removes

all power from board, this is recommended solution for reliable board reboot.

One can expect to see wdog timeout if, for example, not remove all power from board

just performing processor soft reboot.

Best regards
igor
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[SharmaS]

Igor,

Thank you for responding. Much appreciated, indeed.

Would it be possible for you to provide modification(s) to SABRE board schematic to perform processor soft reboot ?

BR,

-Swetang

[igorpadykov]

Hi Swetang

soft reboot not recommended for practical use as it is not reliable.

Reason is that soft reset does not reset all processor peripherals,

details can be found in sect.6.2 System Reset Controller (SRC) i.MX7D

Reference Manual.

Best regards
igor

[SharmaS]

Thank you.