linux-kernel - Re: [PATCH v3 05/10] Documentation: PM: amd-pstate: add debugging section for driver loading failure

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Date: Tue, 11 Jun 2024 14:06:56 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, gautham.shenoy@....com
Cc: rafael.j.wysocki@...el.com, viresh.kumar@...aro.org, Ray.Huang@....com,
 Borislav.Petkov@....com, Alexander.Deucher@....com, Xinmei.Huang@....com,
 Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/10] Documentation: PM: amd-pstate: add debugging
 section for driver loading failure

On 6/11/2024 03:52, Perry Yuan wrote:
> To address issues with the loading of the amd-pstate driver on certain platforms,
> It needs to enable dynamic debugging to capture debug messages during the driver
> loading process. By adding "amd_pstate.dyndbg=+p cppc_acpi.dyndbg=+p  loglevel=4 debug
> amd_pstate=active" to the kernel command line, driver debug logging is enabled.

Here's some suggestion for text.

"
On some platforms if amd-pstate fails to load or operate properly users 
will need to turn on extra debugging messages.
"

However - I would argue that the messages are the wrong level if they 
need debugging messages turned on when it fails to load.

Something causing a failure to load should be pr_warn() or pr_notice()
IMO.

> 
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> ---
>   Documentation/admin-guide/pm/amd-pstate.rst | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index 1e0d101b020a..de83e742738e 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -472,6 +472,19 @@ operations for the new ``amd-pstate`` module with this tool. ::
>   Diagnostics and Tuning
>   =======================
>   
> +Debugging AMD P-State Driver Loading Issues
> +------------------------------------------
> +
> +On some platforms, there may be issues with the loading of the amd-pstate driver.

This makes it sound like it's by design.  Of course it isn't by design, 
so I would instead say:

"If the amd-pstate driver fails to load, additional debug information 
may be necessary."

> +To capture debug messages for issue analysis, users can add below parameter,
> +"amd_pstate.dyndbg=+p cppc_acpi.dyndbg=+p debug"
> +to the kernel command line. This will enable dynamic debugging and allow better
> +analysis and troubleshooting of the driver loading process.
> +
> +Please note that adding this parameter will only enable debug logging during the
> +driver loading phase and may affect system behavior. Use this option with caution
> +and only for debugging purposes.
> +
>   Trace Events
>   --------------
>