SDAA436 September   2026 DRV8000-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction to Human Machine Interface
  5. 2 Introduction to AM62L
  6. 3 Demo Overview
    1. 3.1 Background
  7. 4 Methods to Reduce Active Power
    1. 4.1 Light Weight Graphics Application
    2. 4.2 Minimal Linux Device Tree
    3. 4.3 Local Power Sleep Controller (LPSC)
    4. 4.4 Reducing Clock Frequencies
    5. 4.5 Auto Clock Gating
    6. 4.6 DDR in Auto Self-Refresh
    7. 4.7 Performance
  8. 5 Demo Specific Optimizations
    1. 5.1 LVGL Application
    2. 5.2 Minimal Device Tree
    3. 5.3 Slow Clock Speed
    4. 5.4 Slow A53 Core Clock Frequency
    5. 5.5 Turn Off One A53 Core
    6. 5.6 Slow DDR Transfer Speed
    7. 5.7 DDR Auto Self-Refresh
    8. 5.8 Auto Clock Gating
    9. 5.9 Slow Panel FPS
  9. 6 Power Data
  10. 7 Implementing Low Powers Modes within an HMI Use Case
  11. 8 Demo Steps
    1. 8.1 System Requirements
    2. 8.2 Prepare the SD Card
      1. 8.2.1 Build the Required Files
        1. 8.2.1.1 Boot Images
        2. 8.2.1.2 U-Boot Commands
        3. 8.2.1.3 GUI Files
        4. 8.2.1.4 Kernel Image, Modules, and Device Tree
        5. 8.2.1.5 Scripts
    3. 8.3 Run the Demo
  12. 9 Summary
  13. 10References
  14. 11Appendix
    1. 11.1  Display Image
    2. 11.2  Minimal Device Tree Patch
    3. 11.3  Slow Clock Frequencies
    4. 11.4  Slow DDR Speed to 800 MT/s Patch
    5. 11.5  Enable Auto Self Refresh for DDR
    6. 11.6  Enable Auto Clock Gating
    7. 11.7  Slow Panel Pixel Clock by Half Patch
    8. 11.8  U-Boot Commands
    9. 11.9  Enable All Power Optimizations and Run lvglsim Binary
    10. 11.10 RPI Touch Display Troubleshooting

4.3 Local Power Sleep Controller (LPSC)

Within the AM62L processor is a Power Sleep Controller (PSC) architecture which is responsible for managing the power and clocking for each peripheral, controller and core. There are multiple PSCs for AM62L, each with its own power domains. To provide more granularity on the control of the components within a PSC, there are child nodes of the power domain called local power sleep controllers (LPSCs) which allows for software control of individual modules.

LPSCs are software controllable except for the 'ALWAYS-ON' domain which cannot be turned off. The Linux device tree will initialize the required clocks for each peripheral. Since the clock will be active, the LPSC will be on, hence the peripheral will be on and consuming power. This also works in reverse where if a device tree node is disabled, then the clock will not be initialized so the LPSC will remain off.

In cases where an LPSC is not described in the device tree, the LPSC state can be changed so that the LPSC is clock gated and the local reset is de-asserted.