drm/i915/guc: A little bit more of doorbell sanitization

Some recent refactoring patches have left the doorbell creation outside
the GuC client allocation, which does not make a lot of sense (a client
without a doorbell is something useless). Move it back there, and
refactor the init_doorbell_hw consequently.

Thanks to this, we can do some other improvements, like hoisting the
check for GuC submission enabled out of the enable function.

v2: Rebased.
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/intel_uc.c

@@ -126,6 +126,7 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 	/* We need to notify the guc whenever we change the GGTT */
 	i915_ggtt_enable_guc(dev_priv);
 
+	if (i915.enable_guc_submission) {
 		/*
 		 * This is stuff we need to have available at fw load time
 		 * if we are planning to enable submission later
@@ -133,6 +134,7 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 		ret = i915_guc_submission_init(dev_priv);
 		if (ret)
 			goto err_guc;
+	}
 
 	/* WaEnableuKernelHeaderValidFix:skl */
 	/* WaEnableGuCBootHashCheckNotSet:skl,bxt,kbl */
@@ -187,6 +189,7 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 err_interrupts:
 	gen9_disable_guc_interrupts(dev_priv);
 err_submission:
+	if (i915.enable_guc_submission)
 		i915_guc_submission_fini(dev_priv);
 err_guc:
 	i915_ggtt_disable_guc(dev_priv);
@@ -210,8 +213,8 @@ void intel_uc_fini_hw(struct drm_i915_private *dev_priv)
 	if (i915.enable_guc_submission) {
 		i915_guc_submission_disable(dev_priv);
 		gen9_disable_guc_interrupts(dev_priv);
-	}
 		i915_guc_submission_fini(dev_priv);
+	}
 	i915_ggtt_disable_guc(dev_priv);
 }