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Title: Major Issues Following Release of 5.15.0-160-generic Status in linux package in Ubuntu: New Bug description: Summary: Kernel 5.15.0-160-generic causes black screen on boot - AMD Renoir graphics (ThinkPad T14s Gen 1) Description: System Information Hardware: Lenovo ThinkPad T14s Gen 1 (AMD) GPU: AMD Renoir [1002:1636] (rev d3) OS: Linux Mint 21.2 Victoria (based on Ubuntu 22.04 LTS) Affected Kernel: 5.15.0-160-generic Working Kernel: 5.15.0-157-generic Date Issue Occurred: October 18, 2025 Problem Description After the automatic kernel update to 5.15.0-160-generic (released October 16, 2025), the system became completely unusable with a black screen on boot. The login screen never appears, and the system is inaccessible via normal boot methods. Symptoms Black screen after GRUB menu selection (no video output) System appears to hang during boot process Only accessible via recovery mode with nomodeset parameter Brightness controls (Fn+F5/F6) non-functional AMD GPU driver (amdgpu) fails to initialize Technical Details Error Messages in dmesg: [drm:amdgpu_init [amdgpu]] ERROR VGACON disables amdgpu kernel modesetting. This error appears multiple times during boot, indicating that the VGA console driver (VGACON) is taking control before amdgpu can initialize, preventing proper graphics initialization. GPU Detection: 06:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Renoir [1002:1636] (rev d3) Boot Parameters (Failed Boot): BOOT_IMAGE=/boot/vmlinuz-5.15.0-160-generic root=UUID=f43b6f6c-720a-4568-947b-fa182efb4811 ro quiet splash Loaded Modules (Recovery Mode): When booted in recovery mode with nomodeset, amdgpu module is present but not loaded. Only basic framebuffer drivers (drm, drm_kms_helper) are active. Impact Severity: Critical - System completely unusable Time Lost: Approximately 9-10 hours of troubleshooting User Impact: Unable to work, required advanced Linux knowledge to recover Accessibility: Recovery required understanding of GRUB, kernel parameters, and initramfs This is particularly severe because: No warning was provided before the kernel update System automatically selected the broken kernel as default GRUB menu was hidden by default (GRUB_TIMEOUT=0, GRUB_TIMEOUT_STYLE=hidden) Standard GRUB access keys (ESC/Shift) did not work Required hardware-specific boot menu access (F12) to recover Root Cause Analysis The kernel regression appears to be a driver initialization race condition where VGACON (VGA console driver) claims the graphics hardware before amdgpu can initialize with kernel mode setting (KMS). Once VGACON has control, it refuses to relinquish it to amdgpu, resulting in no functional graphics output. Workaround Applied The following steps were required to restore system functionality: Removed incorrect GRUB parameters Previous troubleshooting attempts had added: amdgpu.si_support=1 amdgpu.cik_support=1 These parameters are for older AMD GPUs (Southern Islands/Sea Islands 2011-2013) and are inappropriate for Renoir (2020). They were removed, leaving only: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" Configured early amdgpu loading Added amdgpu to initramfs to ensure it loads before VGACON: echo "amdgpu" >> /etc/initramfs-tools/modules Enabled explicit kernel modesetting Created modprobe configuration: echo "options amdgpu modeset=1" > /etc/modprobe.d/amdgpu-kms.conf Rebuilt initramfs and updated GRUB sudo update-initramfs -u -k all sudo update-grub Set working kernel as default Locked system to boot kernel 5.15.0-157-generic by name: sudo grub-set-default "gnulinux-5.15.0-157-generic-advanced-f43b6f6c-720a-4568-947b-fa182efb4811" Made GRUB menu visible Changed GRUB configuration to provide safety net: GRUB_TIMEOUT=10 #GRUB_TIMEOUT_STYLE=hidden (commented out) Verification After applying workaround and booting kernel 5.15.0-157-generic: System boots normally to login screen amdgpu driver loads successfully (verified with lsmod | grep amdgpu) No VGACON errors in dmesg Brightness controls functional (Fn+F5/F6) Boot parameters: ro quiet splash (no nomodeset required) Graphics fully functional Comparison: Working vs Broken Kernel Kernel 5.15.0-157-generic (WORKS): uname -r 5.15.0-157-generic lsmod | grep amdgpu amdgpu 9904128 20 drm 622592 11 gpu_sched,drm_kms_helper,amdgpu,drm_ttm_helper,ttm dmesg | grep -i "amdgpu|vgacon" | grep -i error (no errors) Kernel 5.15.0-160-generic (BROKEN): Black screen on boot Cannot capture logs due to inaccessibility Recovery mode shows repeated VGACON errors amdgpu fails to initialize Related Information Similar Reports Other users have reported similar issues with kernel 5.15.0-160-generic: System freezes on AMD hardware Boot failures requiring recovery mode Black screen issues on various AMD GPU configurations Affected Hardware This likely affects: Lenovo ThinkPad T14s Gen 1 (AMD) with Renoir graphics Other systems with AMD Renoir APUs (4000-series mobile) Potentially other AMD Ryzen + Vega configurations Requests Immediate (Urgent): Fix kernel 5.15.0-161+ to resolve AMD Renoir initialization issues Do NOT remove kernel 5.15.0-157 from repositories until fix is confirmed and tested Mark kernel 5.15.0-160 as problematic in update manager for affected hardware Long-term (Important): Implement kernel rollback mechanism - Allow users to easily revert to previous kernel if system won't boot Add kernel update warnings - Notify users before kernel changes default boot option Improve GRUB accessibility - Ensure GRUB menu is accessible (don't hide by default, or ensure key intercept works) Better pre-release testing - Test on common hardware configurations (ThinkPads are extremely common) Hardware-specific kernel holds - Allow users to "pin" kernels for specific hardware Additional Context This bug represents a severe regression that makes systems completely unusable. Users without advanced Linux knowledge would be unable to recover their systems and might: Reinstall the operating system (losing data and configuration) Switch to another OS out of frustration Require professional technical support Be unable to access their computers for critical work The lack of warning, combined with automatic kernel selection and hidden GRUB menu, created a perfect storm that locked users out of their own systems. Testing Offer I am willing to test proposed fixes for kernel 5.15.0-161+ on my hardware and provide detailed feedback. Expected Behavior: System should boot normally to login screen with full graphics functionality. Actual Behavior: Black screen, no video output, system completely inaccessible via normal boot. Reproducibility: 100% reproducible - every boot attempt with kernel 5.15.0-160-generic results in black screen. 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