AM6411: Sleep mode

Hi Harsha,

Harsha Sukeerthi C N said:

I can enter sleep mode with “echo mem >> /sys/power/state” command, but how do exit from this mode?  Currently I am resetting the board for startup.  Only supported sleep mode is s2idle in AM64xx.

Unless other devices such as AM62x/AM62Ax/AM62P, AM64x doesn't support any Low Power mode, so Low Power mode operations such as command 'echo mem > /sys/power/state' are not supported on AM64x devices.

Harsha Sukeerthi C N said:

Power management modes are disabled for Linux RT kernel, and enabled only in general purpose kernel, any specific reason for that?

Power management often adjusts the CPU frequency which would impact interrupt latency. The main goal in RT kernel is to control the interrupt latency, so PM is disabled in RT kernel.

Hi Bin Liu,

Thanks for the reply.

Regarding sleep mode, does it mean, even s2idle (state S0) is not supported by AM64xx?  Because as per kernel documentation, this is minimum that should be supported by all systems, whereas state S1 (standby), S3 (suspend to RAM / deep) and S4 (suspend to disk / disk) are platform dependent.

root@am64xx-evm:/sys/power# cat mem_sleep
[s2idle]

root@am64xx-evm:/sys/power# echo mem >> state
[ 3663.031177] PM: suspend entry (s2idle)
[ 3663.035320] Filesystems sync: 0.000 seconds
[ 3666.278658] k3-m4-rproc 5000000.m4fss: k3_m4_rproc_stop: timedout waiting for rproc completion event
[ 3666.287856] remoteproc remoteproc0: can't stop rproc: -16
[ 3666.293338] Freezing user space processes
[ 3666.299712] Freezing user space processes completed (elapsed 0.002 seconds)
[ 3666.306755] OOM killer disabled.
[ 3666.309974] Freezing remaining freezable tasks
[ 3666.315898] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[ 3666.323331] printk: Suspending console(s) (use no_console_suspend to debug)

After this step, eth0 and eth1 stopped working, and system appears to be in sleep / freeze state.

Regards,

Harsha

Hi Harsha,

s2idle is not validated in the Processor SDK for AM64x. Since the AM64x device doesn't support any Low Power mode, there is no software requirement in the Processor SDK to support any power mode.

From your s2idle log, it seems the system is in sleep, now the question is how/what event to trigger resume.

Hi Bin Liu,

Yes, that was my first question.  Maybe I give MCU WAKEUP GPIO a try?  Similar to 3.2.2.11.6. Wakeup Sources — Processor SDK AM62x Documentation.

Regards,

Harsha

Hi Harsha,

You might first try to use RTC for wakeup:

# rtcwake -m mem -s 5

You might also want to measure the power consumption before "echo mem > /sys/power/state" and after entered s2idle, to see how much power it saves. If not much, it doesn't make sense to figure out wakeup events.

Hi Bin Liu,

I have SK-AM64, which does not have RTC, so cannot use rtcwake option to wake up, but I do agree with measuring power consumption, will try that first.

Regards,

Harsha

Hi Bin Liu,

On the SK-AM64, power consumption reduced from 3W to 1W after executing "echo mem > /sys/power/state".  So, only question is, does it support wakeup events to resume from s2idle case, for which I would need your input.

Regards,

Harsha

Hi Harsha,

Any Low Power mode function has not been exercised in Processor SDK for AM64x. I don't know what could wake up from s2idle.

What wakeup event do you plan to use in your project? So that I can check with our sw dev team.

Hi Bin Liu,

We plan to use wakeup via GPIO.

Regards,

Harsha

Hi Harsha,

Again, since don't exercise LPM on AM64x, I am not sure if this will work, but can you please try the instruction in the link below for MCU GPIO wakeup for AM62x to see if also works for s2idle on AM64x?

https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/09_02_01_09/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Power_Management/pm_wakeup_sources.html#mcu-gpio

Hi Bin Liu,

Tried using GPIO0_8 of MCU as wakeup:

diff --git a/arch/arm64/boot/dts/ti/k3-am642-sk.dts b/arch/arm64/boot/dts/ti/k3-am642-sk.dts
index de0ff5af5..73f4319a0 100644
--- a/arch/arm64/boot/dts/ti/k3-am642-sk.dts
+++ b/arch/arm64/boot/dts/ti/k3-am642-sk.dts
@@ -231,6 +231,21 @@ led-7 {
 			gpios = <&exp2 7 GPIO_ACTIVE_HIGH>;
 		};
 	};
+
+	mcu_gpio_key {
+		compatible = "gpio-keys";
+		autorepeat;
+		pinctrl-names = "default";
+		pinctrl-0 = <&wake_mcugpio1_pins_default>;
+		interrupt-parent = <&mcu_gpio0>;
+		interrupts = <8 IRQ_TYPE_EDGE_RISING>;
+		switch {
+			label = "MCUGPIO";
+			linux,code = <143>;
+			gpios = <&mcu_gpio0 8 GPIO_ACTIVE_LOW>;
+			wakeup-source;
+		};
+	};
 };
 
 &main_pmx0 {
@@ -350,6 +365,14 @@ AM64X_IOPAD(0x00bc, PIN_INPUT, 7) /* (U8) GPIO0_46 */
 	};
 };
 
+&mcu_pmx0 {
+	wake_mcugpio1_pins_default: wake-mcugpio1-pins-default {
+		pinctrl-single,pins = <
+			AM64X_MCU_IOPAD(0x0020, PIN_INPUT, 7) /* (C7) MCU_GPIO0_8 */
+		>;
+	};
+};
+
 &main_uart0 {
 	status = "okay";
 	pinctrl-names = "default";
@@ -387,9 +410,12 @@ exp2: gpio@60 {
 	};
 };
 
-/* mcu_gpio0 is reserved for mcu firmware usage */
 &mcu_gpio0 {
-	status = "reserved";
+	status = "okay";
+};
+
+&mcu_gpio_intr {
+	status = "okay";
 };
 
 &sdhci0 {

GPIO0_8 is pin 3 on SK-AM64 MCU connector.  When I short GPIO0_8 (pin 3) with pin 1 on MCU connector, I don't see wakeup trigger.

root@am64xx-evm:~# cat /proc/interrupts | grep MCUGPIO
318: 0 0 GPIO 8 Edge -davinci_gpio MCUGPIO

Using gpio utilities:

root@am64xx-evm:~# gpiodetect
gpiochip0 [0-0070] (8 lines)
gpiochip1 [4201000.gpio] (23 lines)
gpiochip2 [600000.gpio] (87 lines)
gpiochip3 [601000.gpio] (88 lines)

I see MCU GPIO's are mapped to gpiochip1.  Below is output of gpioinfo command.

gpiochip0 - 8 lines:
line 0: "GPIO_CPSW2_RST" unused input active-high
line 1: "GPIO_CPSW1_RST" unused input active-high
line 2: "PRU_DETECT" unused input active-high
line 3: "MMC1_SD_EN" "fixed-regulator-sd" output active-high [used]
line 4: "VPP_LDO_EN" unused input active-high
line 5: "RPI_PS_3V3_En" unused input active-high
line 6: "RPI_PS_5V0_En" unused input active-high
line 7: "RPI_HAT_DETECT" unused input active-high
gpiochip1 - 23 lines:
line 0: unnamed unused input active-high
line 1: unnamed unused input active-high
line 2: unnamed unused input active-high
line 3: unnamed unused input active-high
line 4: unnamed unused input active-high
line 5: unnamed unused input active-high
line 6: unnamed unused input active-high
line 7: unnamed unused input active-high
line 8: unnamed "MCUGPIO" input active-low [used]
line 9: unnamed unused input active-high
line 10: unnamed unused input active-high
line 11: unnamed unused input active-high
line 12: unnamed unused input active-high
line 13: unnamed unused input active-high
line 14: unnamed unused input active-high
line 15: unnamed unused input active-high
line 16: unnamed unused input active-high
line 17: unnamed unused input active-high
line 18: unnamed unused input active-high
line 19: unnamed unused input active-high
line 20: unnamed unused input active-high
line 21: unnamed unused input active-high
line 22: unnamed unused input active-high

When I try to read GPIO status from gpioget, it throws an error:

root@am64xx-evm:~# gpioget 1 8
gpioget: error reading GPIO values: Device or resource busy

I believe since gpioget and gpioset are failing from main domain, mcu wakeup is also not detected.

Regards,

Harsha

Hi Harsha,

Once a GPIO pin is defined as "gpio-keys" in device tree, the GPIO is then used by the gpio-keys driver, you cannot use user space gpio* commands on this pin. You just need to manually drive the pin to 3.3v or GND to trigger interrupts. Hopefully its interrupt can wakeup from s2idle.

Harsha Sukeerthi C N said:

GPIO0_8 is pin 3 on SK-AM64 MCU connector.  When I short GPIO0_8 (pin 3) with pin 1 on MCU connector, I don't see wakeup trigger.

The schematics shows GPIO0_8 is pin5 on MCU connector, isn't it?

Hi Bin Liu,

Sorry for the earlier typo on my part on GPIO0_8 pin, I am working with pin 5 on MCU connector.  I connected pin 5 to pin 1, I don't see wakeup trigger, and on pin 1, I see 3.3V.

Regards,

Harsha

Hi Harsha,

Can you please try to connect pin 5 to pin 2 which is GND to see if it triggers the wakeup event?