iMX6S watchdog reboot issue

[haidoan]

Hi All,

We are encountering an intermittent issue with watchdog reboot issue on custom board using iMX6S and PMIC MMPF0100.

Our custom board is designed base on SABRE-SD board, with regards to below reboot circuit.

Found out in some instances, the reboot command could not work due to WDOG_BUF signal could not go down to logic 0, hence no change on PWRON pin. It results as system hang forever after enter reboot command.

We have tried with 1uF or 2.2uF but the issue still can happen. Any advice what to check? Thanks.

[igorpadykov]

Hi Hai

probably C504 was not discharged before reboot, what is voltage on

WDOG_B, could you check waveform by oscilloscope.

Best regards
igor

[phuocdo]

Hi Igor,

      Thank for your reply. Here is waveform at WDOG_B pin when the issue happened. 

    Pic 1: waveform at WDOG_B pin of 4 reboot times. 

     Pic 2: zoom of 1 pulse.

    Looking forward to your advice!

Best regards

Phuoc Do

[igorpadykov]

Hi Phuoc

please take waveform at WDOG_BUF pin and then

disconnect C504 and take the same waveforms on WDOB_B signal.

One can try to increase drive strength of WDOB_B signal using

Pad Control Register IOMUXC_SW_PAD_CTL_PAD_X_Y.

Best regards
igor

[phuocdo]

Hi Igor,

      I can not reproduce this issue again, so I can not take waveform at WDOG_BUF pin. 

      And the waveform at WDOB_B pin after I disconnected C504:

     

      where is Pad Control Register in kernel 3.10.17 source?  

Best regards

Phuoc Do

[igorpadykov]

Hi Phuoc

please check pinctrl in board dts file

linux-2.6-imx.git - Freescale i.MX Linux Tree 

Best regards
igor

[phuocdo]

Hi Igor, 

     Thank you so much!

Best regards

Phuoc Do