Re: [PATCH 1/2] drm/i915: Introduce execlist_port_* accessors

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

On Thu, 2017-10-19 at 17:39 +0300, Mika Kuoppala wrote:
> From: Mika Kuoppala <mika.kuoppala@intel.com>
> 
> Instead of trusting that first available port is at index 0,
> use accessor to hide this. This is a preparation for a
> following patches where head can be at arbitrary location
> in the port array.
> 
> v2: improved commit message, elsp_ready readability (Chris)
> v3: s/execlist_port_index/execlist_port (Chris)
> v4: rebase to new naming
> v5: fix port_next indexing
> 
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>

<SNIP>

> @@ -561,15 +563,20 @@ static void port_assign(struct execlist_port *port,
>  static void i915_guc_dequeue(struct intel_engine_cs *engine)
>  {
>  	struct intel_engine_execlists * const execlists = &engine->execlists;
> -	struct execlist_port *port = execlists->port;
> +	struct execlist_port *port;
>  	struct drm_i915_gem_request *last = NULL;
> -	const struct execlist_port * const last_port =
> -		&execlists->port[execlists->port_mask];
>  	bool submit = false;
>  	struct rb_node *rb;
>  
> -	if (port_isset(port))
> -		port++;
> +	port = execlists_port_head(execlists);
> +
> +	/*
> +	 * We don't coalesce into last submitted port with guc.
> +	 * Find first free port, this is safe as we dont dequeue without
> +	 * atleast last port free.

"at least" + "the"

<SNIP>

> @@ -557,6 +557,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  	if (!rb)
>  		goto unlock;
>  
> +	port = execlists_port_head(execlists);
> +	last = port_request(port);
> +
>  	if (last) {
>  		/*
>  		 * Don't resubmit or switch until all outstanding
> @@ -564,7 +567,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  		 * know the next preemption status we see corresponds
>  		 * to this ELSP update.
>  		 */
> -		if (port_count(&port[0]) > 1)
> +		if (port_count(port) > 1)
>  			goto unlock;
>  
>  		if (can_preempt(engine) &&
> @@ -598,7 +601,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  			 * the driver is unable to keep up the supply of new
>  			 * work).
>  			 */
> -			if (port_count(&port[1]))
> +			if (port_count(execlists_port_next(execlists, port)))
>  				goto unlock;
>  
>  			/* WaIdleLiteRestore:bdw,skl
> @@ -634,7 +637,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  				 * combine this request with the last, then we
>  				 * are done.
>  				 */
> -				if (port == last_port) {
> +				if (port == execlists_port_tail(execlists)) {
>  					__list_del_many(&p->requests,
>  							&rq->priotree.link);

Nothing to fix related to this patch, but I was sure next hunk was
going to escape my screen :) Maybe we need to cut the indents a bit.

> @@ -890,7 +902,7 @@ static void intel_lrc_irq_handler(unsigned long data)
>  			}
>  
>  			/* After the final element, the hw should be idle */
> -			GEM_BUG_ON(port_count(port) == 0 &&
> +			GEM_BUG_ON(port_count(execlists_port_head(execlists)) == 0 &&
>  				   !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));

Why did you stop trusting port variable here?

Other than that, looks good to me.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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