[Bug 216163] New: cstates: intel_idle.max_cstate=4 required to eliminate flickering of the display on the laptop model 3Logic Group Graviton N15i-K2

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=216163

            Bug ID: 216163
           Summary: cstates: intel_idle.max_cstate=4 required to eliminate
                    flickering of the display on the laptop model 3Logic
                    Group Graviton N15i-K2
           Product: Drivers
           Version: 2.5
    Kernel Version: v5.18
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Platform_x86
          Assignee: drivers_platform_x86@kernel-bugs.osdl.org
          Reporter: kovalev@altlinux.org
        Regression: No

Created attachment 301249
  --> https://bugzilla.kernel.org/attachment.cgi?id=301249&action=edit
Limiting the list of states for the model processor INTEL_FAM6_KABYLAKE_L

After booting the system almost immediately (it takes less than 1 minute),
there are short-term shutdowns of the display (up to 3 seconds). The problem
disappears if I load the kernel with the parameter intel_idle.max_cstate=4.

While debugging the kernel, I determined that the processor model ID is 0x8E,
defined a macro in the header file /arch/x86/include/asm/intel-family.h :

...
#define INTEL_FAM6_KABYLAKE_L           0x8E    /* Sky Lake             */
/*                 AMBERLAKE_L          0x8E       Sky Lake -- s: 9     */
/*                 COFFEELAKE_L         0x8E       Sky Lake -- s: 10    */
/*                 WHISKEYLAKE_L        0x8E       Sky Lake -- s: 11,12 */
...

And I created a patch with a reduced number of states (4 states) of downtime
for this model, which works successfully.

I am attaching a patch and asking you to consider the feasibility of such a
solution.

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