mx8mm: u-boot: psci doesn't reset the board without WDOG_B

[flaviosuligoi]

Hi all,

I removed both all wdogs initialization and the pinmux setting for WDOG_B pin and the board reset doesn't work anymore. It hangs after calling the function "invoke_psci_fn" with the parameter "PSCI_0_2_FN_SYSTEM_RESET", so I deduce that the PSCI fw is not able to reset the CPU.

If I re-enable only the pinmux setting for WDOG_B pin, the reset works.

My question is: is the PSCI firmware, for the function "PSCI_0_2_FN_SYSTEM_RESET", able to move the WDOG_B pin and so it needs this pin to reset the board?

Regards,

Flavio

[igorpadykov]

Hi Flavio

without using wdog connections (shortly removing power from all board)

it is not possible to implement reliable reset, as some board components can be left

in random state. NXP boards use reset solution with wdog, on

CPU WDOG_B Reset, PMIC U8C on p.12 spf-SPF-31399 schematic

i.MX 8M Mini Evaluation Kit LPDDR4 Design Files

Best regards
igor

[flaviosuligoi]

Hi Igor,

ok, the best reset solution is using the WDOG_B, but my question is now related to the PSCI fw: 

is the PSCI firmware, for the function "PSCI_0_2_FN_SYSTEM_RESET", able to move the WDOG_B pin and so it needs this pin to reset the board?

In other words, in the kernel, I can remove the wdog1 from the machine_restart notifiers chain and use the wdog1 for other purposes, since the PSCI_0_2_FN_SYSTEM_RESET function uses the WDOG_B on its own?

Thanks,

Flavio

[igorpadykov]

Hi Flavio

sorry I could not understand question. So You wish to remove WDOG_B

from PSCI firmware ?

https://source.codeaurora.org/external/imx/imx-atf/tree/plat/imx/imx8m/imx8mm/imx8mm_psci.c?h=imx_5....

Best regards
igor

[flaviosuligoi]

Hi Igor,

I don't want to remove the WDOG_B from the PSCI fw, I'd like only to understand why, when the board is rebooted by the PSCI fw, the WDOG_B toggles. I suppose that the fw moves it, right?

Regards,

Flavio

[igorpadykov · Accepted solution]

Hi Flavio

what bsp used in the case, one can try to debug it starting from nxp codes:

https://source.codeaurora.org/external/imx/imx-atf/tree/plat/imx/imx8m/imx8mm/imx8mm_psci.c?h=imx_5....

use AN4553 Using Open Source Debugging Tools for Linux on i.MX Processors
https://www.nxp.com/docs/en/application-note/AN4553.pdf

Best regards
igor

[flaviosuligoi]

Hi Igor,

ok, I'll analyze in details the sources of the imx-atf code.

Thanks,

Flavio