Linux/AM3352: WDT during system suspend

Ravikiran HV

Part Number: AM3352

Tool/software: Linux

Hello TI,

WE have noticed that WDT1 (Public watchdog) enters suspend mode during system suspend/DS0. (we are using echo mem > /sys/power/state command).
But, we would like to keep WDT ON during suspend, so that any issues in sleep/wakeup should reboot the system. [We are okay to wake up once in a while to refresh/ping the WDT].

We tried to disable WDT1 suspend by forcing module clock (32K_CLK) ON & WDT module mode is forced to NO_IDLE (in omap_hwmod as well using devnmem2 register writes). But we observed that WCCR (wdt counter) value is unchanged during DS0/standby (however it works normally when system is awake).

Any suggestion ? Is that influenced by M3 firmware by any means ?

Thanks

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

What is the source of your 32kHz clock? If it's sourced from the Peripheral PLL it will be switched off in DeepSleep0.

0 Ravikiran HV over 7 years ago in reply to Biser Gatchev-XID

Mastermind 8715 points

HI Biser,

Thanks for the quick reply.

We are using "CLK_32KHZ" from PRCM.

CLKSEL_WDT1_CLK register is set to 0x1 which Select 32KHZ from 32K Clock divider.

0 Biser Gatchev-XID over 7 years ago in reply to Ravikiran HV

TI__Guru**** 393215 points

OK, but this clock comes from the Peripheral PLL, which is switched to bypass in DeepSleep0. Additionally OSC0, which feeds the Peripheral PLL is also switched off in DeepSleep0, so you have no functional clock to the WDT is this state.

0 Ravikiran HV over 7 years ago in reply to Biser Gatchev-XID

Mastermind 8715 points

Is there any possibility to connect to RTC_32K clock o wdt? (rtc iuses OSC1 in our case) ?

According to TRM, WDT1 is in wakeup domain (like GPIO0). So, I am expecting a way to force WDT on during DS0.

0 Biser Gatchev-XID over 7 years ago in reply to Ravikiran HV

TI__Guru**** 393215 points

See Table 20-100 in the AM335x TRM Rev. P. It's either the Peripheral PLL divider or the internal RC oscillator.

Processors

Processors forum

Linux/AM3352: WDT during system suspend