drm/i915/uc: Simplify firmware path handling

Currently fw->path values can represent one of three possible states:

 1) NULL - device without the uC
 2) '\0' - device with the uC but have no firmware
 3) else - device with the uC and we have firmware

Second case is used only to WARN at a later stage.

We can WARN right away and merge cases 1 and 2.

Code can be even further simplified and common (HuC/GuC logic) happening
right before the fetch can be offloaded to the common function.

v2: fewer temporary variables, more straightforward flow (M. Wajdeczko)
v3: DRM_ERROR instead of WARN (M. Wajdeczko)
v4: coding standard (J. Lahtinen)
v5: non-trivial rebase
v6: remove path check, we are checking fetch status (M. Wajdeczko)

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/intel_guc_loader.c

@@ -368,13 +368,6 @@ int intel_guc_init_hw(struct intel_guc *guc)
 		intel_uc_fw_status_repr(guc->fw.fetch_status),
 		intel_uc_fw_status_repr(guc->fw.load_status));
 
-	if (!fw_path) {
-		return -ENXIO;
-	} else if (*fw_path == '\0') {
-		WARN(1, "No GuC firmware known for this platform!\n");
-		return -ENODEV;
-	}
-
 	if (guc->fw.fetch_status != INTEL_UC_FIRMWARE_SUCCESS)
 		return -EIO;
 
@@ -399,7 +392,6 @@ int intel_guc_init_hw(struct intel_guc *guc)
 	return 0;
 }
 
-
 /**
  * intel_guc_init_fw() - select and prepare firmware for loading
  * @guc:	intel_guc struct
@@ -412,37 +404,31 @@ int intel_guc_init_hw(struct intel_guc *guc)
 void intel_guc_init_fw(struct intel_guc *guc)
 {
 	struct drm_i915_private *dev_priv = guc_to_i915(guc);
-	const char *fw_path;
+
+	guc->fw.path = NULL;
+	guc->fw.fetch_status = INTEL_UC_FIRMWARE_NONE;
+	guc->fw.load_status = INTEL_UC_FIRMWARE_NONE;
+	guc->fw.fw = INTEL_UC_FW_TYPE_GUC;
 
 	if (IS_SKYLAKE(dev_priv)) {
-		fw_path = I915_SKL_GUC_UCODE;
+		guc->fw.path = I915_SKL_GUC_UCODE;
 		guc->fw.major_ver_wanted = SKL_FW_MAJOR;
 		guc->fw.minor_ver_wanted = SKL_FW_MINOR;
 	} else if (IS_BROXTON(dev_priv)) {
-		fw_path = I915_BXT_GUC_UCODE;
+		guc->fw.path = I915_BXT_GUC_UCODE;
 		guc->fw.major_ver_wanted = BXT_FW_MAJOR;
 		guc->fw.minor_ver_wanted = BXT_FW_MINOR;
 	} else if (IS_KABYLAKE(dev_priv)) {
-		fw_path = I915_KBL_GUC_UCODE;
+		guc->fw.path = I915_KBL_GUC_UCODE;
 		guc->fw.major_ver_wanted = KBL_FW_MAJOR;
 		guc->fw.minor_ver_wanted = KBL_FW_MINOR;
 	} else {
-		fw_path = "";	/* unknown device */
-	}
-
-	guc->fw.path = fw_path;
-	guc->fw.fetch_status = INTEL_UC_FIRMWARE_NONE;
-	guc->fw.load_status = INTEL_UC_FIRMWARE_NONE;
-
-	if (fw_path == NULL)
-		return;
-	if (*fw_path == '\0')
+		DRM_ERROR("No GuC firmware known for platform with GuC!\n");
+		i915.enable_guc_loading = 0;
 		return;
+	}
 
-	guc->fw.fetch_status = INTEL_UC_FIRMWARE_PENDING;
-	DRM_DEBUG_DRIVER("GuC firmware pending, path %s\n", fw_path);
 	intel_uc_prepare_fw(dev_priv, &guc->fw);
-	/* status must now be FAIL or SUCCESS */
 }
 
 /**

drivers/gpu/drm/i915/intel_huc.c

@@ -155,7 +155,6 @@ static int huc_ucode_xfer(struct drm_i915_private *dev_priv)
 void intel_huc_init_fw(struct intel_huc *huc)
 {
 	struct drm_i915_private *dev_priv = huc_to_i915(huc);
-	const char *fw_path = NULL;
 
 	huc->fw.path = NULL;
 	huc->fw.fetch_status = INTEL_UC_FIRMWARE_NONE;
@@ -163,29 +162,21 @@ void intel_huc_init_fw(struct intel_huc *huc)
 	huc->fw.fw = INTEL_UC_FW_TYPE_HUC;
 
 	if (IS_SKYLAKE(dev_priv)) {
-		fw_path = I915_SKL_HUC_UCODE;
+		huc->fw.path = I915_SKL_HUC_UCODE;
 		huc->fw.major_ver_wanted = SKL_HUC_FW_MAJOR;
 		huc->fw.minor_ver_wanted = SKL_HUC_FW_MINOR;
 	} else if (IS_BROXTON(dev_priv)) {
-		fw_path = I915_BXT_HUC_UCODE;
+		huc->fw.path = I915_BXT_HUC_UCODE;
 		huc->fw.major_ver_wanted = BXT_HUC_FW_MAJOR;
 		huc->fw.minor_ver_wanted = BXT_HUC_FW_MINOR;
 	} else if (IS_KABYLAKE(dev_priv)) {
-		fw_path = I915_KBL_HUC_UCODE;
+		huc->fw.path = I915_KBL_HUC_UCODE;
 		huc->fw.major_ver_wanted = KBL_HUC_FW_MAJOR;
 		huc->fw.minor_ver_wanted = KBL_HUC_FW_MINOR;
-	}
-
-	huc->fw.path = fw_path;
-
-	if (fw_path == NULL)
+	} else {
+		DRM_ERROR("No HuC firmware known for platform with HuC!\n");
 		return;
-
-	huc->fw.fetch_status = INTEL_UC_FIRMWARE_PENDING;
-
-	DRM_DEBUG_DRIVER("HuC firmware pending, path %s\n", fw_path);
-
-	WARN(huc->fw.path == NULL, "HuC present but no fw path\n");
+	}
 
 	intel_uc_prepare_fw(dev_priv, &huc->fw);
 }

drivers/gpu/drm/i915/intel_uc.c

@@ -268,8 +268,10 @@ void intel_uc_prepare_fw(struct drm_i915_private *dev_priv,
 	size_t size;
 	int err;
 
+	uc_fw->fetch_status = INTEL_UC_FIRMWARE_PENDING;
+
 	DRM_DEBUG_DRIVER("before requesting firmware: uC fw fetch status %s\n",
-		intel_uc_fw_status_repr(uc_fw->fetch_status));
+			 intel_uc_fw_status_repr(uc_fw->fetch_status));
 
 	err = request_firmware(&fw, uc_fw->path, &pdev->dev);
 	if (err)