drm/i915: Add missing ring_mask to Pineview

It appears that we never told Pineview it has a RENDER_RING. This was
all fine until we started using the ring_mask for determining all the
available rings to initialise for legacy ringbuffer submission in commit
88d2ba2e ("drm/i915: Unify engine init loop"). Though really it is a
latent bug since the ring_mask inception in commit 73ae478c
("drm/i915: Replace has_bsd/blt/vebox with a mask").

To prevent similar mishaps in future, add a WARN_ON() if we find
ourselves with a device without any rings.

Fixes: 73ae478c ("drm/i915: Replace has_bsd/blt/vebox with a mask")
Fixes: 88d2ba2e ("drm/i915: Unify engine init loop")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ben Widawsky <ben@bwidawsk.net>
Link: http://patchwork.freedesktop.org/patch/msgid/1469749535-2382-1-git-send-email-chris@chris-wilson.co.ukReviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: drm-intel-fixes@lists.freedesktop.org

drivers/gpu/drm/i915/i915_pci.c

@@ -173,6 +173,7 @@ static const struct intel_device_info intel_pineview_info = {
 	.gen = 3, .is_g33 = 1, .is_pineview = 1, .is_mobile = 1, .num_pipes = 2,
 	.need_gfx_hws = 1, .has_hotplug = 1,
 	.has_overlay = 1,
+	.ring_mask = RENDER_RING,
 	GEN_DEFAULT_PIPEOFFSETS,
 	CURSOR_OFFSETS,
 };

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -114,6 +114,7 @@ int intel_engines_init(struct drm_device *dev)
 	unsigned int i;
 	int ret;
 
+	WARN_ON(INTEL_INFO(dev_priv)->ring_mask == 0);
 	WARN_ON(INTEL_INFO(dev_priv)->ring_mask &
 		GENMASK(sizeof(mask) * BITS_PER_BYTE - 1, I915_NUM_ENGINES));