Re: [PATCH 14/19] drm/i915: Move context initialisation to first-use

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On ke, 2016-04-20 at 19:42 +0100, Chris Wilson wrote:
> Instead of allocating a new request when allocating a context, use the
> request that initiated the allocation to emit the context
> initialisation. This serves two purposes, it makes the initialisation
> atomic with first use (simplifying scheduling and our own error
> handling). Secondly, it enables us to remove the explicit context
> allocation required by higher levels of GEM and make that property of
> execlists opaque (in the next patch). There is also a minor step
> forwards towards convergence of legacy/execlist contexts.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Nitpick below.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/i915_drv.h  |  1 +
>  drivers/gpu/drm/i915/intel_lrc.c | 39 ++++++++++++++++++---------------------
>  2 files changed, 19 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 2bf3a8f97d52..e4b510bcee62 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -868,6 +868,7 @@ struct intel_context {
>  		struct i915_vma *lrc_vma;
>  		u64 lrc_desc;
>  		uint32_t *lrc_reg_state;
> +		bool initialised;
>  	} engine[I915_NUM_ENGINES];
>  
>  	struct list_head link;
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 838abd4b42a3..d765267153c5 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -672,9 +672,10 @@ static int execlists_move_to_gpu(struct drm_i915_gem_request *req,
>  
>  int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request)
>  {
> -	int ret = 0;
> +	struct intel_engine_cs *engine = request->engine;
> +	int ret;
>  
> -	request->ringbuf = request->ctx->engine[request->engine->id].ringbuf;
> +	request->ringbuf = request->ctx->engine[engine->id].ringbuf;
>  
>  	if (i915.enable_guc_submission) {
>  		/*
> @@ -689,7 +690,20 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
>  			return ret;
>  	}
>  
> -	return intel_lr_context_pin(request->ctx, request->engine);
> +	ret = intel_lr_context_pin(request->ctx, engine);
> +	if (ret)
> +		return ret;
> +
> +	if (!request->ctx->engine[engine->id].initialised) {
> +		ret = engine->init_context(request);
> +		if (ret) {
> +			intel_lr_context_unpin(request->ctx, engine);

I prefer the goto teardown path, it's easy to read and modify later on.

> +			return ret;
> +		}
> +		request->ctx->engine[engine->id].initialised = true;
> +	}
> +
> +	return 0;
>  }
>  
>  static int logical_ring_wait_for_space(struct drm_i915_gem_request *req,
> @@ -2634,25 +2648,8 @@ int intel_lr_context_deferred_alloc(struct intel_context *ctx,
>  
>  	ctx->engine[engine->id].ringbuf = ringbuf;
>  	ctx->engine[engine->id].state = ctx_obj;
> +	ctx->engine[engine->id].initialised = engine->init_context == NULL;
>  
> -	if (ctx != ctx->i915->kernel_context && engine->init_context) {
> -		struct drm_i915_gem_request *req;
> -
> -		req = i915_gem_request_alloc(engine, ctx);
> -		if (IS_ERR(req)) {
> -			ret = PTR_ERR(req);
> -			DRM_ERROR("ring create req: %d\n", ret);
> -			goto error_ringbuf;
> -		}
> -
> -		ret = engine->init_context(req);
> -		i915_add_request_no_flush(req);
> -		if (ret) {
> -			DRM_ERROR("ring init context: %d\n",
> -				ret);
> -			goto error_ringbuf;
> -		}
> -	}
>  	return 0;
>  
>  error_ringbuf:
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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