TDA4 reset command (SMC 0x84000009) issue

xiaowei zeng1

I meet a problem when I reset TDA4.

Before I reset my system, I write UART register UART_MDR1 with the value 0x00000007 to disable UART, and then run SMC (PSCI_SYSTEM_RESET 0x84000009) to reset SoC.

If this operation works in EL1 context mode, the SoC will reset successfully and enter into U-Boot command shell.

However, if the same operation happens in EL1 handler mode, the CPU will dead when run SMC (0x84000009), wihtout any display and not run into U-Boot again. I also tried to not disable UART by MDR1 before SMC command in EL1 handler mode, it worked well and could run into U-Boot command shell again.

I am confused on the operation in different modes(EL1 handler mode and EL1 context mode). Could you give some suggestions?

Thanks

Zeng,Xiaowei

over 4 years ago

0 Srirama Govindarajan over 4 years ago

TI__Expert 8230 points

Can you clarify what you mean by EL1 handler mode and EL1 context mode

Are your tests run from bare-metal environment (run from A72?) or from linux

0 xiaowei zeng1 over 4 years ago in reply to Srirama Govindarajan

Prodigy 70 points

Sorry to use a inaccurate description. It should be EL1 handler mode and EL1 thread mode, as defined in ARMv8 TRM "EL1h" and "EL1t". Only when run smc 0x84000009 in EL1 thread mode will cause the cpu halt.

I run this in VxWorks-7 based on U-Boot (A72). However, I think this command is OS independent, because it runs into ATF at last.

Thanks.

0 Srirama Govindarajan over 4 years ago in reply to xiaowei zeng1

TI__Expert 8230 points

For armv8-a cores(eg. A72), we normally have a EL1 for running OS code, EL2 for hypervisor and EL3 for Secure monitor

EL1 handler and thread modes, i can see for armv8-m cores.

Can you confirm on your intended usage

0 xiaowei zeng1 over 4 years ago in reply to Srirama Govindarajan

Prodigy 70 points

according to armv8-a, EL1 can use two type SP pointer: SP_EL1 or SP_EL0.

The selected stack pointer can be indicated by a suffix to the Exception level:

t h	Indicates use of the SP_EL0 stack pointer. Indicates use of the SP_ELx stack pointer

SP_EL1t uses stack pointer SP_EL0, and SMC 0x84000009 works well.

SP_EL1h uses stack pointer SP_EL1, and SMC 0x84000009 runs to a failure.

0 Srirama Govindarajan over 4 years ago in reply to xiaowei zeng1

TI__Expert 8230 points

Can you check if the calling method is compatible with ATF - the SMC 0x84000009 call is trapped as PSCI call and serviced through ATF.

Has the VxWorks port been validated for inter-op with ATF on armv8a platform before

0 xiaowei zeng1 over 4 years ago in reply to Srirama Govindarajan

Prodigy 70 points

Yes, VxWorks use SMC interface is a mature interface on armv8a platform, and as mentioned, it could works well to reset if I didn't disable UART before calling SMC 0x84000009. That is to say, SMC traps into ATF successfully. I am not sure why disabling UART cause it works unsuccessfully.

0 Srirama Govindarajan over 4 years ago in reply to xiaowei zeng1

TI__Expert 8230 points

So can we confirm if the issue is seen only if UART is disabled before making the SMC call - is there a specific reason why UART has to be disabled before initiating the rest?

I will check on the handling of SCI_SYSTEM_RESET to see if there is an implicit dependency on the UART being enabled for subsequent restart operation

0 xiaowei zeng1 over 4 years ago in reply to Srirama Govindarajan

Prodigy 70 points

yes, only when in EL1 handler mode, if disable UART before SMC would see this issue.

There is no specific reason to disable UART befor SMC. I just do it as I did on other boards to suspend UART driver before reset.

Thanks

0 Karthik Ramanan over 4 years ago

TI__Guru** 113810 points

Unlocking thread

0 Srirama Govindarajan over 4 years ago in reply to Karthik Ramanan

TI__Expert 8230 points

I confirmed that SCI_SYSTEM_RESET results in full reset and shouldnt have any dependency on the UART disable step.

It shouldnt have made any impact

We have not come across any such issue with our testing so far

Can you live with the workaround to not disable UART before issuing the reset command

We will try and devise a similar test as part of future test scope to see if we can recreate the issue at our end

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TDA4 reset command (SMC 0x84000009) issue