[PATCH] drm/i915: Fix some NUM_RING iterators

[Ben Widawsky <benjamin.widawsky@intel.com>]

There are some cases in the code where we need to know how many rings to
iterate over, but cannot use for_each_ring(). These are always error cases
which happen either before ring setup, or after ring teardown (or
reset).

Note, a NUM_RINGS issue exists in semaphores, but this is fixed by the
remaining semaphore patches which Rodrigo will resubmit shortly. I'd
rather see those patches for fixing the problem than fix it here.

I found this initially for the BSD2 case where on the same platform we
can have differing rings. AFAICT however this effects many platforms.

I'd CC stable on this, except I think all the issues have been around
for multiple releases without bug reports.

Compile tested only for now.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 6 +++---
 drivers/gpu/drm/i915/i915_gpu_error.c   | 2 +-
 drivers/gpu/drm/i915/intel_ringbuffer.h | 2 ++
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index b9bac25..0c044a9 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -403,7 +403,7 @@ void i915_gem_context_reset(struct drm_device *dev)
 
 	/* Prevent the hardware from restoring the last context (which hung) on
 	 * the next switch */
-	for (i = 0; i < I915_NUM_RINGS; i++) {
+	for (i = 0; i < I915_ACTIVE_RINGS(dev); i++) {
 		struct intel_engine_cs *ring = &dev_priv->ring[i];
 		struct intel_context *dctx = ring->default_context;
 
@@ -456,7 +456,7 @@ int i915_gem_context_init(struct drm_device *dev)
 	}
 
 	/* NB: RCS will hold a ref for all rings */
-	for (i = 0; i < I915_NUM_RINGS; i++)
+	for (i = 0; i < I915_ACTIVE_RINGS(dev); i++)
 		dev_priv->ring[i].default_context = ctx;
 
 	DRM_DEBUG_DRIVER("%s context support initialized\n", dev_priv->hw_context_size ? "HW" : "fake");
@@ -493,7 +493,7 @@ void i915_gem_context_fini(struct drm_device *dev)
 		i915_gem_object_ggtt_unpin(dctx->obj);
 	}
 
-	for (i = 0; i < I915_NUM_RINGS; i++) {
+	for (i = 0; i < I915_ACTIVE_RINGS(dev); i++) {
 		struct intel_engine_cs *ring = &dev_priv->ring[i];
 
 		if (ring->last_context)
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 86362de..6e5250d 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -848,7 +848,7 @@ static uint32_t i915_error_generate_code(struct drm_i915_private *dev_priv,
 	 * synchronization commands which almost always appear in the case
 	 * strictly a client bug. Use instdone to differentiate those some.
 	 */
-	for (i = 0; i < I915_NUM_RINGS; i++) {
+	for (i = 0; i < I915_ACTIVE_RINGS(dev_priv->dev); i++) {
 		if (error->ring[i].hangcheck_action == HANGCHECK_HUNG) {
 			if (ring_id)
 				*ring_id = i;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index e72017b..67e2919 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -90,6 +90,8 @@ struct  intel_engine_cs {
 	} id;
 #define I915_NUM_RINGS 5
 #define LAST_USER_RING (VECS + 1)
+#define I915_ACTIVE_RINGS(dev) hweight8(INTEL_INFO(dev)->ring_mask)
+
 	u32		mmio_base;
 	struct		drm_device *dev;
 	struct intel_ringbuffer *buffer;
-- 
2.0.0