Re: [PATCH] drm/xe: Initialize freq_lock even with skip_guc_pc

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

On Fri, Jan 12, 2024 at 10:29:50AM -0800, Matt Roper wrote:
> gucpc isn't initialized when skip_guc_pc is used, but some of the sysfs
> frequency entries still try to grab the uninitialized frequency mutex
> before realizing that they need to bail out.  Tweak the init/fini code
> flows so that the mutex is always initialized properly.

hmmm... good catch.
But I honestly don't believe we should be calling/running any function
that is trying to get the freq_lock. If guc pc is skip, why would we try
to communicate with guc to get or set the freq?

The shared buffers are not set and all. We need a deeper decoupling here.
Vinay?

> 
> Fixes: 975e4a3795d4 ("drm/xe: Manually setup C6 when skip_guc_pc is set")
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_pc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
> index f71085228cb3..67ce24fae79d 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
> @@ -964,11 +964,12 @@ void xe_guc_pc_fini(struct xe_guc_pc *pc)
>  
>  	if (xe->info.skip_guc_pc) {
>  		xe_gt_idle_disable_c6(pc_to_gt(pc));
> -		return;
> +		goto out;
>  	}
>  
>  	XE_WARN_ON(xe_guc_pc_gucrc_disable(pc));
>  	XE_WARN_ON(xe_guc_pc_stop(pc));
> +out:
>  	mutex_destroy(&pc->freq_lock);
>  }
>  
> @@ -984,11 +985,11 @@ int xe_guc_pc_init(struct xe_guc_pc *pc)
>  	struct xe_bo *bo;
>  	u32 size = PAGE_ALIGN(sizeof(struct slpc_shared_data));
>  
> -	if (xe->info.skip_guc_pc)
> -		return 0;
> -
>  	mutex_init(&pc->freq_lock);
>  
> +	if (xe->info.skip_guc_pc)
> +		return 0;
> +
>  	bo = xe_managed_bo_create_pin_map(xe, tile, size,
>  					  XE_BO_CREATE_VRAM_IF_DGFX(tile) |
>  					  XE_BO_CREATE_GGTT_BIT);
> -- 
> 2.43.0
>