[PATCH] drm/i915: Flush logical context image out to memory upon suspend

[Chris Wilson]

Before suspend, and especially before building the hibernation image, we
need to context image to be coherent in memory. To do this we require
that we perform a context switch to a disposable context (i.e. the
dev_priv->kernel_context) - when that switch is complete, all other
context images will be complete. This leaves the kernel_context image as
incomplete, but fortunately that is disposable and we can do a quick
fixup of the logical state after resuming.

Testcase: igt/gem_exec_suspend # bsw
References: https://bugs.freedesktop.org/show_bug.cgi?id=96526
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c |  4 +---
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/i915_gem.c | 46 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 15440123e38d..c5b7b8e0678a 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1590,9 +1590,7 @@ static int i915_drm_resume(struct drm_device *dev)
 
 	intel_csr_ucode_resume(dev_priv);
 
-	mutex_lock(&dev->struct_mutex);
-	i915_gem_restore_gtt_mappings(dev);
-	mutex_unlock(&dev->struct_mutex);
+	i915_gem_resume(dev);
 
 	i915_restore_state(dev);
 	intel_opregion_setup(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1ec523d29789..e73c0fc84c73 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3384,6 +3384,7 @@ void i915_gem_init_swizzling(struct drm_device *dev);
 void i915_gem_cleanup_engines(struct drm_device *dev);
 int __must_check i915_gem_wait_for_idle(struct drm_i915_private *dev_priv);
 int __must_check i915_gem_suspend(struct drm_device *dev);
+void i915_gem_resume(struct drm_device *dev);
 void __i915_add_request(struct drm_i915_gem_request *req,
 			struct drm_i915_gem_object *batch_obj,
 			bool flush_caches);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cf0e8aa8035c..8b42a5101f11 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4974,6 +4974,35 @@ i915_gem_stop_engines(struct drm_device *dev)
 		dev_priv->gt.stop_engine(engine);
 }
 
+static int switch_to_kernel_context(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *engine;
+
+	for_each_engine(engine, dev_priv) {
+		struct drm_i915_gem_request *req;
+		int ret;
+
+		if (engine->last_context == NULL)
+			continue;
+
+		if (engine->last_context == dev_priv->kernel_context)
+			continue;
+
+		req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
+		if (IS_ERR(req))
+			return PTR_ERR(req);
+
+		ret = 0;
+		if (!i915.enable_execlists)
+			ret = i915_switch_context(req);
+		i915_add_request_no_flush(req);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int
 i915_gem_suspend(struct drm_device *dev)
 {
@@ -4983,6 +5012,10 @@ i915_gem_suspend(struct drm_device *dev)
 	intel_suspend_gt_powersave(dev_priv);
 
 	mutex_lock(&dev->struct_mutex);
+	ret = switch_to_kernel_context(dev_priv);
+	if (ret)
+		goto err;
+
 	ret = i915_gem_wait_for_idle(dev_priv);
 	if (ret)
 		goto err;
@@ -5009,6 +5042,19 @@ err:
 	return ret;
 }
 
+void i915_gem_resume(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+
+	mutex_lock(&dev->struct_mutex);
+
+	if (i915.enable_execlists)
+		intel_lr_context_reset(dev_priv, dev_priv->kernel_context);
+
+	i915_gem_restore_gtt_mappings(dev);
+	mutex_unlock(&dev->struct_mutex);
+}
+
 void i915_gem_init_swizzling(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
-- 
2.8.1