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[#1]

Guidance for Low Power Mode on i.MX8MP

Hi NXP Team,

I am working on a custom product based on i.MX8M Plus (i.MX8MP) using Yocto Linux and BusyBox userspace.

Current hardware configuration:

• i.MX8MP
• LA9410 connected through PCIe
• LTE modem (u-blox LARA-L6) connected through USB
• MIPI CSI camera connected to i.MX8MP
• Yocto BSP based Linux
• BusyBox rootfs

Project requirement:
We need to implement low power operation with:

1. Low latency wakeup
2. Fast resume back to normal operation
3. PCIe and USB subsystem stability after resume
4. Camera pipeline recovery after wakeup
5. LTE modem reconnect/resume support

We are currently evaluating:

• WAIT mode
• STOP mode
• DSM (Deep Sleep Mode)

From the Reference Manual and AN13400, DSM gives maximum power saving, but our concern is wakeup latency and peripheral resume stability.

Main questions:

1. Which low power mode is recommended for this use case?
   • WAIT
   • STOP
   • DSM
2. For low latency wakeup with PCIe + USB + camera active systems, is suspend-to-idle preferred over deep suspend?
3. Are there any known limitations for:
   • PCIe device resume (LA9310)
   • USB LTE modem resume
   • CSI camera recovery after suspend
4. Which BSP version/kernel is most stable for low power support on i.MX8MP?
   We are currently considering:
   • LF 6.6.3 BSP
   • Yocto Nanbield
5. Are there recommended SDKs, patches, or reference implementations for:
   • PCIe wakeup
   • USB wakeup
   • Runtime PM
   • DSM entry/exit
   • Low latency suspend/resume
6. Is there any recommended approach for keeping LTE connectivity partially active while reducing overall system power?

Reference documents we are studying:

• AN13400: i.MX 8M Low Power Design By M Core Running
• i.MX8MP Reference Manual Chapter 5 (GPC / Low Power)
• Linux PM framework
• gpcv2 driver

Any guidance, reference SDKs, Yocto layers, example DTS configurations, or suspend/resume debug methods would be very helpful.

Thank you.

FRDM-TrainingHands-On TrainingHW-Open-Sourcei.MX 8 Family | i.MX 8QuadMax (8QM) | 8QuadPlusi.MX 8M | i.MX 8M Mini | i.MX 8M NanoPMICSecuritySuspected Software DefectYocto ProjectRe: Guidance for Low Power Mode on i.MX8MP

Hi,
1. I would recommend Runtime PM first, use runtime PM/autosuspend for individual subsystems while Linux is running:

• PCIe endpoint idle handling, need PCIe endpoint driver support: https://docs.kernel.org/power/pci.html
• USB modem autosuspend / remote wakeup: linux/Documentation/driver-api/usb/power-management.rst
• camera stream stop / sensor power management, should be shutdown before IDLE/SLEEP
• CPU idle / DVFS

2. For short idle periods and fast wakeup, use Linux suspend-to-idle. DSM only for long idle / maximum power saving

3. For  the BSP verison, recommend to use latest version.

Best Regards,
Zhiming