20% power consumption increase in Yocto 5.0(6.6.52-2.2.0) on NXP i.MX 8M Plus EVK

[richard_hu]

Dear sir,

We have observed a 20% increase in power consumption during idle mode when comparing Yocto 4.0 (kernel 5.15.71-2.2.2) to Yocto 5.0 (kernel 6.6.52-2.2.0) on the NXP i.MX 8M Plus EVK.

Specifically, the measured power consumption during idle mode is as follows:

	Yocto 4.0(kernel 5.15.71-2.2.2)	Yocto 5.0(kernel 5.15.71-2.2.2)
Idle, Power consumption (measured on power-supply)	5V, 413 mA	5V, 510 mA

Both tests were conducted using the prebuilt images downloaded from the NXP official website without any modifications:

• LF_v5.15.71-2.2.2_images_IMX8MPEVK.zip
• LF_v6.6.52-2.2.0_images_IMX8MPEVK.zip

This increase in power consumption might lead to a temperature difference of approximately 6-7 degrees Celsius on our custom board.

We have noted that the CPU usage and frequency remain similar between the two versions.

Could you please assist us in identifying the cause of this power consumption difference? Your insights would be greatly appreciated.

BR,

Richard

[richard_hu]

Sorry. There is typo in kernel version in the table.
It should be corrected as below:

	Yocto 4.0(kernel 5.15.71-2.2.2)	Yocto 5.0(kernel 6.6.52-2.2.0)
Idle, Power consumption (measured on power-supply)	5V, 413 mA	5V, 510 mA

[danielchen]

HI @richard_hu 

could you please send me the scripts you are using in version 6.6.52 to me for reproduce the issue?

Regards

Daniel

[richard_hu]

@danielchen 

Thanks for the reply.
It doesn't need additional script.
We observe this phenomenon when the system is in idle.
Just need to boot the board with linux 6.6.52 and check the output power from power supply.

BR,

Richard

[danielchen]

Hi @richard_hu :

Please refer to the result on my side.

BSP 5.4.70:

 BSP 6.6.52

Please let me know the detailed steps to reproduce this issue .

Regards

Daniel

[richard_hu]

@danielchen

Thank you for your great assistance.

I have summarized the PMIC output measurements for average power consumption and have prepared a comparison table below:

Location	Yocto 4.0 (5.4) Avg Power (mW)	Yocto 5.0 (6.6) Avg Power (mW)	Difference (mW)	Change
A vdd_arm	9.36	24.19	14.83	Increased
B nvcc_dram_1v1	31.39	73.78	42.39	Increased
C vsys_5v	616.06	1791.75	1175.69	Increased
D vdd_soc	196.95	1044.86	847.91	Increased
E lpdd4_vddq	2.34	0.75	-1.59	Reduced
lpdd4_vdd2	5.54	1.78	-3.76	Reduced
nvcc_sd2	2.31	2.31	0.00	-
vdd_lvds_1v8	0.02	0.02	0.00	-
vdd_hdmi_1v8	0.00	12.61	12.61	Increased
I nvcc_snvs_1v8	0.20	0.4	0.20	Increased
vdd_earc_1v8	0.00	0.01	0.01	Increased
vdd_usb_1v8	0.32	3.42	3.10	Increased
vdd_pci_1v8	0.00	80.68	80.68	Increased
vdd_mipi_1v8	0.14	0.15	0.01	Increased
O vdd_pll_ana_1v8	15.72	15.57	-0.15	Reduced
nvcc_sd1	1.74	1.71	-0.03	Reduced
lpdd4_vdd1	3.03	2.96	-0.07	Reduced
cpu_vdd_1v8	4.02	0.82	-3.20	Reduced
bb_vdd_1v8	41.23	43.82	2.59	Increased
vdd_pll_ana_0v8	2.34	3.09	0.75	Increased
vdd_pci_0v8	2.60	51.7	49.10	Increased
vdd_mipi_0v8	0.24	0.63	0.39	Increased
vdd_hdmi_0v8	1.19	37.58	36.39	Increased
vdd_usb_3v3	13.17	81.48	68.31	Increased
vdd_usb_0v8	2.55	20.44	17.89	Increased
vdd_sd1_3v3	-1.14	0.68	1.82	Increased
bb_vdd_3v3	215.53	45.06	-170.47	Reduced
**Totals**			**2358.42**	**Increased**
			**-179.27**	**Reduced**
**Net Difference**

It appears that vsys_5v and vdd_soc have increased by approximately 2022 mW in the Linux 6.6 kernel.

Could you provide any insights into the possible causes of this increase?

Additionally, could you measure the total power consumption for the entire NXP i.MX 8M Plus EVK using the power adapter output?

Thank you for your attention to this matter.

BR,

Richard

[danielchen]

Hi @richard_hu 

The power consumption is highly dependent on the application.

Since there is a big change between the two BSP versions.     the device tree are also different.  It is hard to make a simple comparison.  Please refer to the total power consumption I tested on BSP 6.6.52,  idle.

I will update if I have new findings.

Regards

Daniel

Regards

Daniel

[richard_hu]

@danielchen 

Thanks for your help.

It looks the latest measurement, the vdd_soc values have returned to a level similar to that of Linux 5.4.7. However, the current vsys_5v value (1004mW) remains higher than the baseline measurement under Linux 5.4.7 (616mW).

Looking forward to your analysis, and thank you for your expertise in resolving this.

BR,

Richard

[danielchen · Accepted solution]

Hi @richard_hu :

This power consumption increase is resulted from the new drivers were introduced in the new version: --PCIe / HDMI.   If I disable the two device in dtb file,  the power consumption will be close to that in BSP 5.4.70.

Regards

Daniel

[richard_hu]

@danielchen
Thanks for the excellent support and thoughtful input

We can confirm that the issue is attributable to the PCIe interface. Below are the key findings from our analysis:

Test Results:

1. PCIe Disabled:
   When PCIe is disabled, the power consumption difference between Linux kernel versions 5.15.71-2.2.2 and 6.6.52-2.2.0 is minimal (only 15 mA at 12V).

2. NVMe SSD Read/Write Testing:
   Under active workloads (NVMe SSD read/write operations), the power consumption remains consistent across both kernel versions when PCIe is enabled.

Hypothesized Cause:

As you suggested, this discrepancy may stem from the migration to the mainline kernel-based PCIe driver. Our investigation indicates that the issue arises specifically when:

• Certain PCIe-related IP blocks or clock gating mechanisms remain active, even in the absence of a connected device.

This suggests that the power consumption increase is tied to residual activity in the PCIe subsystem under these conditions.

BR,

Richard

[danielchen]

Hi Richard:

Thanks for letting us know that,  I will setup an environment to test it on my side, will keep you updated. 

Regards

Daniel