Re: [RFC 7/9] drm/xe/gt_tlb_invalidation_ggtt: Call xe_force_wake_put if xe_force_wake_get succeds

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

On Fri, Aug 30, 2024 at 10:53:24AM +0530, Himal Prasad Ghimiray wrote:
> A failure in xe_force_wake_get() no longer increments the domain's
> refcount, so xe_force_wake_put() should not be called in such cases
> 
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> index cca9cf536f76..3f86ab704c4f 100644
> --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> @@ -259,11 +259,11 @@ static int xe_gt_tlb_invalidation_guc(struct xe_gt *gt,
>  int xe_gt_tlb_invalidation_ggtt(struct xe_gt *gt)
>  {
>  	struct xe_device *xe = gt_to_xe(gt);
> +	int ret;
>  
>  	if (xe_guc_ct_enabled(&gt->uc.guc.ct) &&
>  	    gt->uc.guc.submission_state.enabled) {
>  		struct xe_gt_tlb_invalidation_fence fence;
> -		int ret;
>  
>  		xe_gt_tlb_invalidation_fence_init(gt, &fence, true);
>  		ret = xe_gt_tlb_invalidation_guc(gt, &fence);
> @@ -277,7 +277,9 @@ int xe_gt_tlb_invalidation_ggtt(struct xe_gt *gt)
>  		if (IS_SRIOV_VF(xe))
>  			return 0;
>  
> -		xe_gt_WARN_ON(gt, xe_force_wake_get(gt_to_fw(gt), XE_FW_GT));
> +		ret =  xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
> +		xe_gt_WARN_ON(gt, ret);
> +
>  		if (xe->info.platform == XE_PVC || GRAPHICS_VER(xe) >= 20) {
>  			xe_mmio_write32(gt, PVC_GUC_TLB_INV_DESC1,
>  					PVC_GUC_TLB_INV_DESC1_INVALIDATE);
> @@ -287,7 +289,8 @@ int xe_gt_tlb_invalidation_ggtt(struct xe_gt *gt)
>  			xe_mmio_write32(gt, GUC_TLB_INV_CR,
>  					GUC_TLB_INV_CR_INVALIDATE);
>  		}
> -		xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
> +		if (!ret)
> +			xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);

looking all these cases now I honestly prefer the other way around.

If we called the get, we call the put.
get always increase the reference and put does the clean-up.

fw_ref = xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);

xe_force_wake_put(gt_to_fw(gt), fw_ref);

so, the fw_ref is a mask of the woken up cases which require
the ref drop and sleep call.

>  	}
>  
>  	return 0;
> -- 
> 2.34.1
>