Re: [PATCH v2] drm: Ensure Proper Unload/Reload Order of MEI Modules for i915/Xe Driver

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Sep 09, 2024 at 09:33:17AM +0530, Bommu Krishnaiah wrote:
> This update addresses the unload/reload sequence of MEI modules in relation to
> the i915/Xe graphics driver. On platforms where the MEI hardware is integrated
> with the graphics device (e.g., DG2/BMG), the i915/xe driver is depend on the MEI
> modules. Conversely, on newer platforms like MTL and LNL, where the MEI hardware
> is separate, this dependency does not exist.
> 
> The changes introduced ensure that MEI modules are unloaded and reloaded in the
> correct order based on platform-specific dependencies. This is achieved by adding
> a MODULE_SOFTDEP directive to the i915 and Xe module code.
> 
> These changes enhance the robustness of MEI module handling across different hardware
> platforms, ensuring that the i915/Xe driver can be cleanly unloaded and reloaded
> without issues.
> 
> v2: updated commit message
> 
> Signed-off-by: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
> Cc: Kamil Konieczny <kamil.konieczny@linux.intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Tejas Upadhyay <tejas.upadhyay@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_module.c | 2 ++
>  drivers/gpu/drm/xe/xe_module.c     | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_module.c b/drivers/gpu/drm/i915/i915_module.c
> index 65acd7bf75d0..2ad079ad35db 100644
> --- a/drivers/gpu/drm/i915/i915_module.c
> +++ b/drivers/gpu/drm/i915/i915_module.c
> @@ -75,6 +75,8 @@ static const struct {
>  };
>  static int init_progress;
>  
> +MODULE_SOFTDEP("pre: mei_gsc_proxy mei_gsc");
> +
>  static int __init i915_init(void)
>  {
>  	int err, i;
> diff --git a/drivers/gpu/drm/xe/xe_module.c b/drivers/gpu/drm/xe/xe_module.c
> index bfc3deebdaa2..5633ea1841b7 100644
> --- a/drivers/gpu/drm/xe/xe_module.c
> +++ b/drivers/gpu/drm/xe/xe_module.c
> @@ -127,6 +127,8 @@ static void xe_call_exit_func(unsigned int i)
>  	init_funcs[i].exit();
>  }
>  
> +MODULE_SOFTDEP("pre: mei_gsc_proxy mei_gsc");

I'm honestly not very comfortable with this.

1. This is not true for every device supported by these modules.
2. This is not true for every (and the most basic) functionality of these drivers.

Shouldn't this be done in the the mei side?

Couldn't at probe we identify the need of them and if needed we return -EPROBE to
attempt a retry after the mei drivers were probed?

Cc: Alexander Usyskin <alexander.usyskin@intel.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>

> +
>  static int __init xe_init(void)
>  {
>  	int err, i;
> -- 
> 2.25.1
>