drm/i915: Extract ring init from hw_init

The ring initialization will differ a bit in upcoming generations, and
this split will prepare the code for what's needed.

This patch also fixes a bug introduced in:
commit 9943393195
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Tue Jan 22 14:12:17 2013 +0200

    drm/i915: use gem_set_seqno() on hardware init

After doing the extraction, the bad error handling became obvious.  I
acknowledge that this should be two patches, but it's a pretty
small/trivial patch. If requested, I can certainly do the fix as a
distinct patch.

v2: Should be cleanup blt, not init blt on failure (Chris)

v3: Forgot to git add on v2

Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -3930,22 +3930,11 @@ intel_enable_blt(struct drm_device *dev)
 	return true;
 }
 
-int
-i915_gem_init_hw(struct drm_device *dev)
+static int i915_gem_init_rings(struct drm_device *dev)
 {
-	drm_i915_private_t *dev_priv = dev->dev_private;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
-	if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
-		return -EIO;
-
-	if (IS_HASWELL(dev) && (I915_READ(0x120010) == 1))
-		I915_WRITE(0x9008, I915_READ(0x9008) | 0xf0000);
-
-	i915_gem_l3_remap(dev);
-
-	i915_gem_init_swizzling(dev);
-
 	ret = intel_init_render_ring_buffer(dev);
 	if (ret)
 		return ret;
@@ -3963,6 +3952,38 @@ i915_gem_init_hw(struct drm_device *dev)
 	}
 
 	ret = i915_gem_set_seqno(dev, ((u32)~0 - 0x1000));
+	if (ret)
+		goto cleanup_blt_ring;
+
+	return 0;
+
+cleanup_blt_ring:
+	intel_cleanup_ring_buffer(&dev_priv->ring[BCS]);
+cleanup_bsd_ring:
+	intel_cleanup_ring_buffer(&dev_priv->ring[VCS]);
+cleanup_render_ring:
+	intel_cleanup_ring_buffer(&dev_priv->ring[RCS]);
+
+	return ret;
+}
+
+int
+i915_gem_init_hw(struct drm_device *dev)
+{
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	int ret;
+
+	if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
+		return -EIO;
+
+	if (IS_HASWELL(dev) && (I915_READ(0x120010) == 1))
+		I915_WRITE(0x9008, I915_READ(0x9008) | 0xf0000);
+
+	i915_gem_l3_remap(dev);
+
+	i915_gem_init_swizzling(dev);
+
+	ret = i915_gem_init_rings(dev);
 	if (ret)
 		return ret;
 
@@ -3974,12 +3995,6 @@ i915_gem_init_hw(struct drm_device *dev)
 	i915_gem_init_ppgtt(dev);
 
 	return 0;
-
-cleanup_bsd_ring:
-	intel_cleanup_ring_buffer(&dev_priv->ring[VCS]);
-cleanup_render_ring:
-	intel_cleanup_ring_buffer(&dev_priv->ring[RCS]);
-	return ret;
 }
 
 int i915_gem_init(struct drm_device *dev)