AM620-Q1: Understanding the low power modes

Hello,

I'm looking into this and will get back to you. Please ping the thread if you haven't gotten a response by Thursday.

Thanks,

Anshu

Hello,

Shibi MAnoharan said:

Is it loaded to DDR and M4F executes from DDR?

During MCU Only mode, DDR is in self refresh so nothing will execute from DDR.

Shibi MAnoharan said:

I could see there is no response when any key is pressed in MCU uart. I added debug log continuously in the mcu uart to verify the mcu only mode. But the log stops after 31 counts.

Can you share any changes to code to make the debug log? Which SDK version are you using for this?

Shibi MAnoharan said:

Does Partial IO mode suit this need?

Partial I/O mode will shut off almost the whole SoC expect the CANUART pins. This includes the M4F core. Partial I/O will not wakeup from RTC since the RTC will be off.

For any low power mode applications that require the M4F to be on, MCU Only mode is the suitable option.

Thanks,

Anshu

Please provide answers to all my 6 questions. Thanks in advance.

1. Can you share any changes to code to make the debug log? Which SDK version are you using for this? I initially used 09.01 later used the latest one.

2. Partial I/O mode will shut off almost the whole SoC expect the CANUART pins. This includes the M4F core. Partial I/O will not wakeup from RTC since the RTC will be off. Does any wakeup trigger from Partial IO mode by CANUART pins makes the A53 and M4F core boot. I want to understand specifically if the Linux also boots when any of the IO pin is triggered.

3. Is there a way, like programming the DM / Wake up firmware to modify how the device should wakeup from Partial IO/MCU only mode. Basically, does a customer have control over DM firmware related to wakeup.

Attached below is the code snippet from ipc_rpmsg_echo.c. Highlighted the newly added code.

4. Basically, I added a while loop which will print to the uart continuously with certain delay. I understand the uart blocking call will be called to come out of low power mode. But, I want to confirm if the MCU keeps running in the MCU only mode.

void lpm_mcu_uart_wakeup_task(void* args)
{
int32_t status;
UART_Transaction trans;
uint8_t uartData;
uint32_t count=0;

UART_Transaction_init(&trans);

status = SemaphoreP_constructBinary(&gLpmSuspendSem, 0);
status = SemaphoreP_constructBinary(&gLpmResumeSem, 0);
DebugP_assert(SystemP_SUCCESS == status);

while (1)
{
/* Read 1 byte */
trans.buf = &uartData;
trans.count = 1U;

/* Wait for suspend from linux */
SemaphoreP_pend(&gLpmSuspendSem, SystemP_WAIT_FOREVER);


DebugP_log("[IPC RPMSG ECHO] Suspend request to MCU-only mode received \r\n");
DebugP_log("[IPC RPMSG ECHO] Press a sinlge key on this terminal to resume the kernel from MCU only mode \r\n");

gNumBytesRead = 0u;

while(1)
{
//if(RPMessage_getLocalEndPt(pRpmsgObj) == 13)

DebugP_log("I am running %d\r\n", count++);

uint32_t timeout=0;
while(timeout < 1000000)
timeout++;
}
/* Wait for any key to be pressed */
status = UART_read(gUartHandle[CONFIG_UART0], &trans);
DebugP_assert(status == SystemP_SUCCESS);

while ((gNumBytesRead == 0u) && (gbSuspended == 1u))
{

}

if (gNumBytesRead != 0)
{
DebugP_log("[IPC RPMSG ECHO] Key pressed. Notifying DM to wakeup main domain\r\n");
//SOC_triggerMcuLpmWakeup();
SOC_generateSwWarmResetMainDomainFromMcuDomain();
/* Wait for resuming the main domain */
SemaphoreP_pend(&gLpmResumeSem, SystemP_WAIT_FOREVER);

DebugP_log("[IPC RPMSG ECHO] Main domain resumed due to MCU UART \r\n");
}
else if (gbSuspended == 0u)
{
UART_readCancel(gUartHandle[CONFIG_UART0], &trans);
DebugP_log("[IPC RPMSG ECHO] Main domain resumed from a different wakeup source \r\n");
}

if (gbShutdown == 1u)
{
break;
}
}
SemaphoreP_destruct(&gLpmSuspendSem);
SemaphoreP_destruct(&gLpmResumeSem);
vTaskDelete(NULL);
}

5. what is the difference between SOC_triggerMcuLpmWakeup() and SOC_generateSwWarmResetMainDomainFromMcuDomain()?

6. Is it possible to put the A53 core in powered down instead of suspend to RAM before going into MCU only mode?

Hello,

Are you testing MCU Only mode on a TI EVM or custom board design?

Shibi MAnoharan said:

Does any wakeup trigger from Partial IO mode by CANUART pins makes the A53 and M4F core boot.

Yes, the whole SoC will resume. Please see section 6.2.4 Power Modes in the AM62x TRM: https://www.ti.com/lit/ug/spruiv7b/spruiv7b.pdf

Shibi MAnoharan said:

Is there a way, like programming the DM / Wake up firmware to modify how the device should wakeup from Partial IO/MCU only mode. Basically, does a customer have control over DM firmware related to wakeup.

The wakeup processes are pre-defined in the DM Firmware and not able to be changed. I'll double check on this.

Shibi MAnoharan said:

what is the difference between SOC_triggerMcuLpmWakeup() and SOC_generateSwWarmResetMainDomainFromMcuDomain()?

I recommend you make a seperate thread for this question. This is MCU+ SDK specific question which not in my expertise. You can also look into <MCU+ SDK Directory>/source/drivers/soc/am62x/soc.h for some additional information.

Shibi MAnoharan said:

Is it possible to put the A53 core in powered down instead of suspend to RAM before going into MCU only mode?

No its not possible within MCU Only mode. You can send requests to the DM Firmware to power down the A53 cores, but this is not MCU Only mode.

Thanks,

Anshu

Hi Anshu,

 The wakeup processes are pre-defined in the DM Firmware and not able to be changed. I'll double check on this. Could you please confirm this?

No its not possible within MCU Only mode. You can send requests to the DM Firmware to power down the A53 cores, but this is not MCU Only mode. - What is this mode then?

Are you testing MCU Only mode on a TI EVM or custom board design? - I am testing it in AM62X-SK_LP evk

Hello,

Shibi MAnoharan said:

No its not possible within MCU Only mode. You can send requests to the DM Firmware to power down the A53 cores, but this is not MCU Only mode. - What is this mode then?

This is not a specific low power mode. This is just adjusting what cores are active and which ones are not.

A Low Power Mode will be pre-defined and there isn't flexibility for what cores/peripherals are active and what is not. An Active State allows for this customization. 

Thanks,

Anshu