[PATCH 2/2] drm/i915: Defer late hardware initialisation until first open

[Dave Gordon <david.s.gordon@intel.com>]

We can do less work during driver load by deferring some of it until
the first time the device is opened; in particular, the function
i915_gem_init_hw_late() introduced by the previous patch. This should
allow the system to get out of the early single-threaded phase of
system initialisation and into full multi-user mode somewhat quicker.

In addition, we expect that by the time of the first open, not only
the driver's software structures but also system-specific items such
as filesystem mounting have been fully initialised, meaning that the
late initialisation code can run in a much more complete environment
than the driver_load stage presents. This can be important for
embedded programmable devices that need firmware loaded from a file
before they can be used.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         |    1 +
 drivers/gpu/drm/i915/i915_gem.c         |    4 +++-
 drivers/gpu/drm/i915/i915_gem_context.c |   32 ++++++++++++++++++++++++++-----
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bc7c510..ba63804 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1845,6 +1845,7 @@ struct drm_i915_private {
 	/* hda/i915 audio component */
 	bool audio_component_registered;
 
+	bool contexts_ready;
 	uint32_t hw_context_size;
 	struct list_head context_list;
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1887e60..0cb962f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5073,7 +5073,9 @@ i915_gem_init_hw(struct drm_device *dev)
 			goto out;
 	}
 
-	ret = i915_gem_init_hw_late(dev);
+	/* Don't do late init on the first time through here */
+	if (dev_priv->contexts_ready)
+		ret = i915_gem_init_hw_late(dev);
 
 out:
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index a7e58a8..917c867 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -438,23 +438,45 @@ static int context_idr_cleanup(int id, void *p, void *data)
 	return 0;
 }
 
+/* Complete any late initialisation here */
+static int i915_gem_context_first_open(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int ret;
+
+	ret = i915_gem_init_hw_late(dev);
+	if (ret == 0)
+		dev_priv->contexts_ready = true;
+
+	return ret;
+}
+
 int i915_gem_context_open(struct drm_device *dev, struct drm_file *file)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct intel_context *ctx;
+	int ret = 0;
 
 	idr_init(&file_priv->context_idr);
 
 	mutex_lock(&dev->struct_mutex);
-	ctx = i915_gem_create_context(dev, file_priv);
+
+	if (!dev_priv->contexts_ready)
+		ret = i915_gem_context_first_open(dev);
+
+	if (ret == 0) {
+		ctx = i915_gem_create_context(dev, file_priv);
+		if (IS_ERR(ctx))
+			ret = PTR_ERR(ctx);
+	}
+
 	mutex_unlock(&dev->struct_mutex);
 
-	if (IS_ERR(ctx)) {
+	if (ret)
 		idr_destroy(&file_priv->context_idr);
-		return PTR_ERR(ctx);
-	}
 
-	return 0;
+	return ret;
 }
 
 void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
-- 
1.7.9.5

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