drm/i915: Use request_firmware and our own async work

Two benefits:
- We can use FW_LOADER_USERSPACE_FALLBACK.
- We can use flush_work to synchronize with the oustanding worker,
  which is a notch more obvious what it does than having a special
  completion.

The next patch will properly synchronize against the async loader in
the resume and unload code.

Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Tested-by: Daniel Stone <daniels@collabora.com> # SKL
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446069547-24760-11-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -739,6 +739,7 @@ struct intel_uncore {
 #define CSR_VERSION_MINOR(version)	((version) & 0xffff)
 
 struct intel_csr {
+	struct work_struct work;
 	const char *fw_path;
 	uint32_t *dmc_payload;
 	uint32_t dmc_fw_size;

drivers/gpu/drm/i915/intel_csr.c

@@ -361,11 +361,18 @@ static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
 	return dmc_payload;
 }
 
-static void finish_csr_load(const struct firmware *fw, void *context)
+static void csr_load_work_fn(struct work_struct *work)
 {
-	struct drm_i915_private *dev_priv = context;
-	struct intel_csr *csr = &dev_priv->csr;
+	struct drm_i915_private *dev_priv;
+	struct intel_csr *csr;
+	const struct firmware *fw;
+	int ret;
+
+	dev_priv = container_of(work, typeof(*dev_priv), csr.work);
+	csr = &dev_priv->csr;
 
+	ret = request_firmware(&fw, dev_priv->csr.fw_path,
+			       &dev_priv->dev->pdev->dev);
 	if (!fw)
 		goto out;
 
@@ -401,7 +408,8 @@ static void finish_csr_load(const struct firmware *fw, void *context)
 void intel_csr_ucode_init(struct drm_i915_private *dev_priv)
 {
 	struct intel_csr *csr = &dev_priv->csr;
-	int ret;
+
+	INIT_WORK(&dev_priv->csr.work, csr_load_work_fn);
 
 	if (!HAS_CSR(dev_priv))
 		return;
@@ -423,15 +431,7 @@ void intel_csr_ucode_init(struct drm_i915_private *dev_priv)
 	 */
 	intel_display_power_get(dev_priv, POWER_DOMAIN_INIT);
 
-	/* CSR supported for platform, load firmware */
-	ret = request_firmware_nowait(THIS_MODULE, true, csr->fw_path,
-				      &dev_priv->dev->pdev->dev,
-				      GFP_KERNEL, dev_priv,
-				      finish_csr_load);
-
-	if (ret)
-		DRM_ERROR("Failed to load DMC firmware, disabling rpm (%d)\n",
-			  ret);
+	schedule_work(&dev_priv->csr.work);
 }
 
 /**