DESK-MX9-L/Deployment/Power Manager

History
Issue Date	Notes
2024/04/02	Power Manager documentation

Power Manager

Operational characteristics

The power consumption measurements for AURA SOM are executed with 3.3 V power supply.

Power consumption

There are various operating modes available.

Attention: the SOC used does not support the DVFS and therefore the use of the governor present in the Linux kernel, instead of this functionality to scale the performance to have lower consumption by the SOC there is a new technology the Low Drive mode.

Low Drive mode

Documentation from NXP:

• i.MX93 datasheet
• AN13917: i.MX 93 Reducing the power Consumption
• AN13917: i.MX 93 Power Architecture

There are four operating modes(Not all present by default on Aura SOM):

Mode	VDD SOC	A55 Max Frequency	DRAM Max Frequency	Note
Over drive (OD Mode, default)	0.9 V	1700 MHz	1866 MHz (3733 MTS)	(1)(2)
Nominal drive (ND Mode)	0.85 V	1400 MHz	1400 MHz (2800 MTS)	-
Low drive (LD Mode) (1)	0.8 V	933 MHz	933 MHz (1866 MTS)	(3)
Low drive (LD Mode) (2)	0.8 V	933 MHz	625 MTS	(3)

Note:

• (1): Over drive is the default operating mode
• (2): Over drive can be disabled, see here
• (3): Low drive need to be activated from device tree by default these are not present, see here

Device Tree

To enable/disable and configure the driver the device tree must used: by default the node lpm present on arch/arm64/boot/dts/freescale/imx93.dtsi is disabled, then the Low Drive Mode is disabled.

By default, on Aura SOM the support is enabled with minimal configuration to have:

• Over drive Mode
• Nominal drive Mode

To do this see arch/arm64/boot/dts/freescale/imx93-aura.dtsi:

...
&lpm {
	soc-supply = <&buck1>;
	status = "okay";
};
...
&lpi2c2 {
        ....
	pmic@25 {
		compatible = "nxp,pca9451a";
                ...
		regulators {
			buck1: BUCK1 {
				...
			};
		...
		};
	...
	};
};
...

The node to change the SOC voltage supply needs the PMIC buck regulator reference on Aura SOM the PMIC Buck used is Buck1.

Enable Low drive Mode

To enable the two modalities Low drive Mode add the property ld-mode-enabled on lpm node of the device tree.

By default on Aura SOM these modalities are disabled.

Attention: if you want to add these modalities, properly check if you must change the clock rate for the other peripherals like:

• flexspi1 to 266000000
• usdhc1 to 266000000
• usdhc2 to 266000000
• usdhc3 to 266000000

See also the NXP EVK here arch/arm64/boot/dts/freescale/imx93-11x11-evk-ld.dts

Disable Over drive Mode

To disable the Over drive Mode and have by default the Nomial drive Mode add the property no-od-mode on lpm node of device tree.

Command

The driver/imx/soc/imx93_lpm.c driver uses imx-atf to manage the operating mode and can be controlled using a sysfs interface.

Read the current mode:

root@desk-mx93-rev0:~# cat /sys/devices/platform/imx93-lpm/mode
System is in OD mode with DDR 3733 MTS!

Read the current clock of core.

root@desk-mx93-rev1:~# mhz
1690 MHz, 0.5917 nanosec clock

To change on Over drive Mode:

root@desk-mx93-rev1:~# echo 0 > /sys/devices/platform/imx93-lpm/mode
[ 9456.025419] System switching to OD mode...
root@desk-mx93-rev1:~# cat /sys/devices/platform/imx93-lpm/mode
System is in OD mode with DDR 3733 MTS!
root@desk-mx93-rev1:~# mhz
1690 MHz, 0.5917 nanosec clock

To change on Nominal drive Mode:

root@desk-mx93-rev1:~# echo 1 > /sys/devices/platform/imx93-lpm/mode
[ 9557.112015] System switching to ND mode...
root@desk-mx93-rev1:~# cat /sys/devices/platform/imx93-lpm/mode
System is in ND mode with DDR 1866 MTS!
root@desk-mx93-rev1:~# mhz
1398 MHz, 0.7153 nanosec clock

To change on Low drive Mode (1866 MTS) (Modality not present by default):

root@desk-mx93-rev1:~# echo 2 > /sys/devices/platform/imx93-lpm/mode
[ 9623.164150] System switching to LD/SWFFC mode...
root@desk-mx93-rev1:~# cat /sys/devices/platform/imx93-lpm/mode
System is in LD mode with DDR 1866 MTS!
root@desk-mx93-rev1:~# mhz
898 MHz, 1.1136 nanosec clock

To change on Low drive Mode (625 MTS) (Modality not present by default):

root@desk-mx93-rev1:~# echo 3 > /sys/devices/platform/imx93-lpm/mode
[ 9648.546368] System switching to LD/SWFFC mode...
root@desk-mx93-rev1:~# cat /sys/devices/platform/imx93-lpm/mode
System is in LD mode with DDR 625 MTS!
root@desk-mx93-rev1:~# mhz
898 MHz, 1.1136 nanosec clock

Operational Mode

The typical operating modes envisaged are:

• Quiet-normal (LPM: Over drive)
• Quiet-nominal (LPM: Nominal drive)
• Stressed-normal (LPM: Over drive)
• Stressed-nominal (LPM: Nominal drive)
• Suspend
• Freeze

Setup

The measurements were performed with follow device connected to the board (Only the most energy-intensive devices are listed).

• Eth0 interface up
• Eth1 interface up
• uSD
• DSI-HDMI converter and HDMI display up

Quiet

On quiet the core nt have any additional process/task.

Stressed

To simulate high consumption, the following energy-intensive operations were performed:

• both eth interfaces are configured and an endless iperf3 - with external server support - is executed
• camera streaming a video to the HDMI display
• execute the sat for stressing the SOC and the RAM memory

Then there are four energy-intensive operations.

Measurements

Mode	Current	Power	Diff Normal	Diff Stress
Quiet-normal (LPM: Over drive)	0,5 A	1.65 W	Normal reference	-50% (Reference: Stressed-normal (LPM: Over drive))
Quiet-nominal (LPM: Nominal drive)	0.469 A	1.55 W	-6 %	-32% (Reference: Stressed-nominal (LPM: Nominal drive))
Stressed-normal (LPM: Over drive)	0.75 A	2.475 W	+50%	Stress reference
Stressed-nominal (LPM: Nominal drive)	0.469 A	1.55 W	+24%	-17 %
Suspend	0.046 A	0.152 W	-91 %	-93 %
Freeze	0.179 A	0.59 W	-64 %	-76 %

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