[Bug 221383] ideapad_laptop: Fn hotkeys stop emitting after s2idle resume on IdeaPad Slim 3 14ARP10 (Ryzen 7735HS)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221383

--- Comment #38 from Mario Limonciello (AMD) (mario.limonciello@amd.com) ---
Created attachment 309954
  --> https://bugzilla.kernel.org/attachment.cgi?id=309954&action=edit
patch to force clear EC events on resume

FWIW - I passed your logs and this bug through Claude + the kernel
review-prompts skill (https://github.com/masoncl/review-prompts) with a local
kernel checkout and it at least agrees that this is primarily an EC FW timing
bug.

----
  1. EC Interrupt Blocking: When acpi_ec_enter_noirq() is called during
suspend, the EC driver switches to busy polling mode (ec->busy_polling = true)  
  2. Critical Window: Between EC interrupt blocking and actual suspend entry,
the EC firmware needs time to:
    - Complete any in-flight transactions in polling mode                       
    - Flush internal state                                                      
    - Save hotkey handler state                                                 
    - Prepare for suspend                                                       
  3. The Race:                                                                  
    - Without delay: EC interrupts blocked → system suspends almost immediately
→ EC firmware doesn't complete state save → On resume, EC loses hotkey event
state                                                                           
    - With 2.5s delay: EC interrupts blocked → 2.5s in polling mode → EC
firmware completes state transitions → system suspends → On resume, EC restores
hotkey state correctly                                                          
  4. Why SCI_EVT differs:                                                       
    - In the broken case, the EC firmware lost track of hotkey state during
suspend because it was rushed                                                   
    - In the working case, the EC had time to properly save state and restore
it, so SCI_EVT=1 appears naturally on resume                                    
----

But - that being said I pushed the LLM a little bit more and wonder if maybe
draining the events on resume would help.

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