drm/i915: Mark the current context as lost on suspend

In order to force a reload of the context image upon resume, we first
need to mark its absence on suspend. Currently we are failing to restore
the golden context state and any context w/a to the default context
after resume.

One oversight corrected, is that we had forgotten to reapply the L3
remapping when restoring the lost default context.

v2: Remove deprecated WARN.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-7-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.h

@@ -3293,6 +3293,7 @@ void i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj);
 
 /* i915_gem_context.c */
 int __must_check i915_gem_context_init(struct drm_device *dev);
+void i915_gem_context_lost(struct drm_i915_private *dev_priv);
 void i915_gem_context_fini(struct drm_device *dev);
 void i915_gem_context_reset(struct drm_device *dev);
 int i915_gem_context_open(struct drm_device *dev, struct drm_file *file);

drivers/gpu/drm/i915/i915_gem.c

@@ -4719,6 +4719,7 @@ i915_gem_suspend(struct drm_device *dev)
 	i915_gem_retire_requests(dev);
 
 	i915_gem_stop_engines(dev);
+	i915_gem_context_lost(dev_priv);
 	mutex_unlock(&dev->struct_mutex);
 
 	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);

drivers/gpu/drm/i915/i915_gem_context.c

@@ -90,6 +90,8 @@
 #include "i915_drv.h"
 #include "i915_trace.h"
 
+#define ALL_L3_SLICES(dev) (1 << NUM_L3_SLICES(dev)) - 1
+
 /* This is a HW constraint. The value below is the largest known requirement
  * I've seen in a spec to date, and that was a workaround for a non-shipping
  * part. It should be safe to decrease this, but it's more future proof as is.
@@ -249,7 +251,7 @@ __create_hw_context(struct drm_device *dev,
 	/* NB: Mark all slices as needing a remap so that when the context first
 	 * loads it will restore whatever remap state already exists. If there
 	 * is no remap info, it will be a NOP. */
-	ctx->remap_slice = (1 << NUM_L3_SLICES(dev)) - 1;
+	ctx->remap_slice = ALL_L3_SLICES(dev_priv);
 
 	ctx->hang_stats.ban_period_seconds = DRM_I915_CTX_BAN_PERIOD;
 
@@ -336,7 +338,6 @@ static void i915_gem_context_unpin(struct intel_context *ctx,
 void i915_gem_context_reset(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	int i;
 
 	if (i915.enable_execlists) {
 		struct intel_context *ctx;
@@ -345,17 +346,7 @@ void i915_gem_context_reset(struct drm_device *dev)
 			intel_lr_context_reset(dev_priv, ctx);
 	}
 
-	for (i = 0; i < I915_NUM_ENGINES; i++) {
-		struct intel_engine_cs *engine = &dev_priv->engine[i];
-
-		if (engine->last_context) {
-			i915_gem_context_unpin(engine->last_context, engine);
-			engine->last_context = NULL;
-		}
-	}
-
-	/* Force the GPU state to be reinitialised on enabling */
-	dev_priv->kernel_context->legacy_hw_ctx.initialized = false;
+	i915_gem_context_lost(dev_priv);
 }
 
 int i915_gem_context_init(struct drm_device *dev)
@@ -403,11 +394,29 @@ int i915_gem_context_init(struct drm_device *dev)
 	return 0;
 }
 
+void i915_gem_context_lost(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *engine;
+
+	for_each_engine(engine, dev_priv) {
+		if (engine->last_context == NULL)
+			continue;
+
+		i915_gem_context_unpin(engine->last_context, engine);
+		engine->last_context = NULL;
+	}
+
+	/* Force the GPU state to be reinitialised on enabling */
+	dev_priv->kernel_context->legacy_hw_ctx.initialized = false;
+	dev_priv->kernel_context->remap_slice = ALL_L3_SLICES(dev_priv);
+}
+
 void i915_gem_context_fini(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_context *dctx = dev_priv->kernel_context;
-	int i;
+
+	i915_gem_context_lost(dev_priv);
 
 	if (dctx->legacy_hw_ctx.rcs_state) {
 		/* The only known way to stop the gpu from accessing the hw context is
@@ -415,26 +424,9 @@ void i915_gem_context_fini(struct drm_device *dev)
 		 * other code, leading to spurious errors. */
 		intel_gpu_reset(dev, ALL_ENGINES);
 
-		/* When default context is created and switched to, base object refcount
-		 * will be 2 (+1 from object creation and +1 from do_switch()).
-		 * i915_gem_context_fini() will be called after gpu_idle() has switched
-		 * to default context. So we need to unreference the base object once
-		 * to offset the do_switch part, so that i915_gem_context_unreference()
-		 * can then free the base object correctly. */
-		WARN_ON(!dev_priv->engine[RCS].last_context);
-
 		i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
 	}
 
-	for (i = I915_NUM_ENGINES; --i >= 0;) {
-		struct intel_engine_cs *engine = &dev_priv->engine[i];
-
-		if (engine->last_context) {
-			i915_gem_context_unpin(engine->last_context, engine);
-			engine->last_context = NULL;
-		}
-	}
-
 	i915_gem_context_unreference(dctx);
 	dev_priv->kernel_context = NULL;
 }