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Date:   Tue, 4 Apr 2023 17:39:13 +0200
From:   Andi Shyti <andi.shyti@linux.intel.com>
To:     Andrzej Hajda <andrzej.hajda@intel.com>
Cc:     Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org,
        Chris Wilson <chris.p.wilson@linux.intel.com>,
        Andi Shyti <andi.shyti@linux.intel.com>,
        Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH v2] drm/i915/gt: Hold a wakeref for the active VM
Message-ID: <ZCxEoelnOSpRiy6A@ashyti-mobl2.lan>
References: <20230330-hold_wakeref_for_active_vm-v2-1-724d201499c2@intel.com>
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In-Reply-To: <20230330-hold_wakeref_for_active_vm-v2-1-724d201499c2@intel.com>
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Hi Andrzej,

> diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> index 0a8d553da3f439..48f888c3da083b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> @@ -14,6 +14,7 @@
>  #include "i915_drv.h"
>  #include "intel_context_types.h"
>  #include "intel_engine_types.h"
> +#include "intel_gt_pm.h"
>  #include "intel_ring_types.h"
>  #include "intel_timeline_types.h"
>  #include "i915_trace.h"
> @@ -207,8 +208,11 @@ void intel_context_exit_engine(struct intel_context *ce);
>  static inline void intel_context_enter(struct intel_context *ce)
>  {
>  	lockdep_assert_held(&ce->timeline->mutex);
> -	if (!ce->active_count++)
> -		ce->ops->enter(ce);
> +	if (ce->active_count++)
> +		return;
> +
> +	ce->ops->enter(ce);
> +	intel_gt_pm_get(ce->vm->gt);
>  }
>  
>  static inline void intel_context_mark_active(struct intel_context *ce)
> @@ -222,8 +226,11 @@ static inline void intel_context_exit(struct intel_context *ce)
>  {
>  	lockdep_assert_held(&ce->timeline->mutex);
>  	GEM_BUG_ON(!ce->active_count);
> -	if (!--ce->active_count)
> -		ce->ops->exit(ce);
> +	if (--ce->active_count)
> +		return;
> +
> +	intel_gt_pm_put_async(ce->vm->gt);
> +	ce->ops->exit(ce);

shouldn't these two be swapped?

>  }
>  
>  static inline struct intel_context *intel_context_get(struct intel_context *ce)
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> index e971b153fda976..ee531a5c142c77 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> @@ -114,6 +114,15 @@ __queue_and_release_pm(struct i915_request *rq,
>  
>  	ENGINE_TRACE(engine, "parking\n");
>  
> +	/*
> +	 * Open coded one half of intel_context_enter, which we have to omit
> +	 * here (see the large comment below) and because the other part must
> +	 * not be called due constructing directly with __i915_request_create
> +	 * which increments active count via intel_context_mark_active.
> +	 */
> +	GEM_BUG_ON(rq->context->active_count != 1);
> +	__intel_gt_pm_get(engine->gt);

where is it's brother "put"?

Thanks,
Andi

> +
>  	/*
>  	 * We have to serialise all potential retirement paths with our
>  	 * submission, as we don't want to underflow either the
> 
> ---
> base-commit: 3385d6482cd60f2a0bbb0fa97b70ae7dbba4f95c
> change-id: 20230330-hold_wakeref_for_active_vm-7f013a449ef3
> 
> Best regards,
> -- 
> Andrzej Hajda <andrzej.hajda@intel.com>