Troubleshooting Screen Wake-Up Issues After Rooting Your MTK MT8167 Android 9 Tablet

Rooting an Android device, especially one like an OEM tablet running Android 9 with an MTK MT8167 CPU, can unlock a world of customization and control. However, it can also introduce unexpected problems. One common issue, as experienced by many users, is the tablet becoming unresponsive after entering sleep mode, requiring a power connection to wake the screen, while the ADB connection remains active. At Magisk Modules, we understand these frustrations. This guide provides a comprehensive approach to diagnosing and resolving this specific problem, leveraging our resources at the Magisk Module Repository and our collective expertise.

Understanding the Root Cause: Why Your Screen Won’t Wake Up

Several factors can contribute to a screen failing to wake up after rooting, particularly on devices with MediaTek (MTK) chipsets. These include:

• Kernel Incompatibilities: The root process might introduce modifications that aren’t fully compatible with the device’s kernel, leading to instability and power management issues. This is more prone in devices with customized or OEM ROMs.
• Power Management Conflicts: Magisk modules or Magisk itself may interfere with the device’s built-in power management system, causing the system to incorrectly enter a deep sleep state from which it cannot recover without an external power source.
• Driver Issues: Rooting can sometimes affect the display drivers, particularly if custom kernels or modules are installed. This could hinder the screen’s ability to properly respond to wake-up signals.
• ACPI (Advanced Configuration and Power Interface) Errors: Incorrect ACPI settings, which are common on tablets converted from other uses like cooking devices, can prevent the screen from waking up when the device is running on battery.
• Modified System Files: Improper modification or corruption of system files during the rooting process can lead to a wide range of unexpected behaviors, including display issues.

Step-by-Step Troubleshooting: Diagnosing the Issue

Before diving into solutions, it’s vital to diagnose the problem systematically. This will help you identify the specific cause and choose the most appropriate fix.

1. Checking Basic Connections and Power State

• Verify Battery Level: Ensure the battery isn’t critically low. Although ADB is active, low battery can cause erratic behavior in screen management.
• Inspect Charging Port: Examine the charging port for any debris or damage that might cause intermittent charging.
• Hard Reboot (Simulated Battery Removal): Press and hold the power button for an extended period (20-30 seconds). This sometimes forces a hard reset, similar to removing the battery (if possible). This can force a display output reset.

2. Analyzing ADB Output and Logs

Since ADB is functional, use it to gather more information about the device’s state.

• Logcat Analysis: Use adb logcat to capture system logs after the screen fails to wake up. Look for errors or warnings related to the display, power management, or kernel. Focus on timestamps around the time the device entered sleep mode.

  adb logcat > logcat.txt
  

  Analyze the logcat.txt file for relevant errors.
• Kernel Log (dmesg): Use adb shell dmesg to check the kernel log for any hardware-related errors.

  adb shell dmesg > dmesg.txt
  

  Examine dmesg.txt for potential problems with the display controller or power management.
• Check Power State with dumpsys power: This command provides detailed information about the device’s power state. Look for flags indicating deep sleep, display power status, and wake locks.

  adb shell dumpsys power > power_state.txt
  

  Analyze power_state.txt for anomalies in power management. Look for clues about whether the system is truly asleep or if it’s a display-only issue.
• Check Wake Locks: The command adb shell dumpsys power | grep WakeLocks: can reveal which apps or services are holding wake locks and potentially preventing the device from entering a proper sleep state. This is especially crucial if you have installed any modules or apps after rooting. bash adb shell dumpsys power | grep WakeLocks: Identify any unusual wake locks that might be the cause of the screen not waking up.

3. Identifying Suspect Magisk Modules

• Disable Modules Incrementally: Start by disabling recently installed or updated Magisk modules. After disabling each module, reboot the device and test if the screen wake-up issue is resolved. This process of elimination helps identify the culprit module. You can use Magisk Manager or ADB to disable modules.
• Check Module Compatibility: Review the documentation or support forums for each installed module to check for known compatibility issues with your device model or Android version.
• Look for Modules Affecting Power Management or Display: Modules that directly modify power management settings, kernel parameters, or display drivers are more likely to cause this type of problem.

Solutions: Resolving the Screen Wake-Up Issue

Once you have a better understanding of the cause, try these solutions in order of increasing complexity.

1. Reinstalling Magisk

• Clean Reinstall: A clean reinstall of Magisk can resolve issues caused by corrupted or incorrectly installed files. Download the latest Magisk APK from the official Magisk Module Repository or the official Github page. Uninstall the current version of Magisk through Magisk Manager. Flash the downloaded Magisk ZIP file through your custom recovery (TWRP, etc.). Reboot the device.

2. Adjusting Kernel Parameters (Requires Knowledge of Kernel Tweaking)

• sysctl Configuration: Using ADB shell with root privileges, you can try adjusting kernel parameters related to power management. Create a script with sysctl commands and execute it during boot. For example, try adjusting vm.dirty_expire_centisecs to control how often dirty data is written to disk, which can impact power consumption. Be cautious when modifying kernel parameters, as incorrect settings can cause system instability.

  adb shell
  su
  echo "vm.dirty_expire_centisecs = 3000" > /data/local/tmp/sysctl.conf
  chmod 644 /data/local/tmp/sysctl.conf
  # Use a Magisk module or init.d script to apply the sysctl settings on boot
  

• Kernel Tweaking Apps: Apps like Kernel Adiutor (available on the Magisk Module Repository) allow you to adjust kernel settings without manually editing configuration files. Use these apps with caution and research safe settings for your specific device model.

3. Power Management Configuration (Advanced)

• Editing power_profile.xml: This file contains power consumption values for different hardware components. Modifying it incorrectly can lead to instability or reduced battery life. Back up the original file before making any changes. This typically resides in /system/framework/. You will need root access to modify it. Use a text editor to carefully adjust values.
• Examining and Modifying build.prop: The build.prop file contains system properties that can affect power management. Adding or modifying properties related to sleep modes or display settings might resolve the issue. Again, back up the original file before making changes. Example: Adding ro.ril.power_collapse=1 might help.

4. Custom Kernel Flashing (Expert Users Only)

• Find a Compatible Kernel: If the stock kernel is the source of the problem, consider flashing a custom kernel that is specifically designed for your device model and Android version. Custom kernels often include optimized power management settings and bug fixes.
• Research and Due Diligence: Thoroughly research any custom kernel before flashing it. Ensure it is compatible with your device and Android version, and that it comes from a reputable source. Incorrect kernels can brick your device.

5. Addressing ACPI Issues (If Applicable)

• ACPI Table Modification (Extremely Advanced): If you suspect that ACPI settings are causing the problem (particularly on tablets converted from other purposes), you might need to modify the ACPI tables. This requires advanced knowledge of ACPI specifications and can be risky. Tools like ACPICA can be used to disassemble and reassemble ACPI tables. Only attempt this if you are highly experienced with low-level system modifications.

6. Downgrading or Changing Root Method

• Try a Different Root Method: If Magisk is consistently causing problems, explore alternative root methods for your device. Some devices might be more stable with other root solutions. However, this is usually not applicable for MTK devices.
• Reverting to Stock ROM: As a last resort, consider reverting to the stock ROM. This will remove root access but might resolve the screen wake-up issue if it is caused by modifications introduced during the rooting process. This can verify if the hardware is properly working or not.

Preventative Measures: Avoiding Future Issues

• Research Thoroughly: Before rooting any device, research the process thoroughly and check for known issues specific to your device model and Android version.
• Backup Everything: Always create a full backup of your device before making any modifications. This allows you to restore your device to its original state if something goes wrong.
• Install Modules Carefully: Only install Magisk modules from trusted sources. Review the module’s documentation and user reviews before installing it.
• Monitor System Logs: Regularly monitor system logs for any errors or warnings. This can help you identify potential problems early on.

Specific Considerations for MTK MT8167 Devices

The MTK MT8167 chipset is commonly found in budget-friendly tablets and devices. These devices often have customized ROMs and less community support compared to flagship devices. Therefore, finding specific solutions for your device might be challenging.

• Check MTK-Specific Forums: Search for forums or communities dedicated to MTK devices. These forums might contain information about common issues and solutions for your specific chipset.
• Look for Custom ROMs: Explore whether there are custom ROMs available for your device. A custom ROM might provide better stability and compatibility compared to the stock ROM. However, ensure the custom ROM is specifically designed for your device model.

Where to Find Help and Resources

• Magisk Module Repository: Find useful Magisk modules and resources.
• XDA Developers Forum: A vast resource for Android development and troubleshooting.
• Reddit (r/Magisk, r/AndroidRoot): Online communities where you can ask for help and share your experiences.
• GitHub: Search for repositories related to Magisk modules or custom kernels for your device.

We at Magisk Modules are committed to helping you get the most out of your rooted devices. This comprehensive guide offers a structured approach to troubleshoot the screen wake-up issue, equipping you with the knowledge and tools to resolve the problem and regain full control over your Android tablet. Remember to proceed with caution, back up your data, and thoroughly research any modifications before implementing them.

Disclamer

Modifying system files and flashing custom kernels can be risky and may void your device’s warranty. We are not responsible for any damage caused to your device as a result of following this guide. Proceed at your own risk.