[PATCH v4 3/3] DO NOT MERGE: add enable_guc_loading parameter

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

Split the function of "enable_guc_submission" into two separate options.
The new one "enable_guc_loading" controls only the *fetching and loading*
of the GuC firmware image. The existing one is redefined to control only
the *use* of the GuC for batch submission once the firmware is loaded.

In addition, the degree of control has been refined from a simple bool
to an integer key, allowing several options:
 -1  (default)    whatever the platform default is
  0  DISABLE      don't load/use the GuC
  1  BEST EFFORT  try to load/use the GuC, fallback if not available
  2  REQUIRE      must load/use the GuC, else leave the GPU wedged

The new platform default (as coded here) will be to attempt to load
the GuC iff the device has a GuC that requires firmware, to attempt to
use it iff the device has a GuC that supports the submission protocol
(with or without firmware), and to fall back to execlist mode if any
required firmware cannot be found or fails to load.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>

---
 drivers/gpu/drm/i915/i915_gem.c         |  1 -
 drivers/gpu/drm/i915/i915_params.c      | 14 ++++-
 drivers/gpu/drm/i915/i915_params.h      |  3 +-
 drivers/gpu/drm/i915/intel_guc_loader.c | 98 ++++++++++++++++++---------------
 4 files changed, 67 insertions(+), 49 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ca96fc1..da34db5 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4885,7 +4885,6 @@ int i915_gem_init_engines(struct drm_device *dev)
 		ret = intel_guc_ucode_load(dev);
 		if (ret) {
 			DRM_ERROR("Failed to initialize GuC, error %d\n", ret);
-			ret = -EIO;
 			goto out;
 		}
 	}
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 1779f02..21f325b 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -54,7 +54,8 @@ struct i915_params i915 __read_mostly = {
 	.verbose_state_checks = 1,
 	.nuclear_pageflip = 0,
 	.edp_vswing = 0,
-	.enable_guc_submission = false,
+	.enable_guc_loading = -1,
+	.enable_guc_submission = -1,
 	.guc_log_level = -1,
 	.enable_dp_mst = true,
 	.inject_load_failure = 0,
@@ -197,8 +198,15 @@ struct i915_params i915 __read_mostly = {
 		 "(0=use value from vbt [default], 1=low power swing(200mV),"
 		 "2=default swing(400mV))");
 
-module_param_named_unsafe(enable_guc_submission, i915.enable_guc_submission, bool, 0400);
-MODULE_PARM_DESC(enable_guc_submission, "Enable GuC submission (default:false)");
+module_param_named_unsafe(enable_guc_loading, i915.enable_guc_loading, int, 0400);
+MODULE_PARM_DESC(enable_guc_submission,
+		"Enable GuC firmware loading "
+		"(-1=auto [default], 0=never, 1=if available, 2=required)");
+
+module_param_named_unsafe(enable_guc_submission, i915.enable_guc_submission, int, 0400);
+MODULE_PARM_DESC(enable_guc_submission,
+		"Enable GuC submission "
+		"(-1=auto [default], 0=never, 1=if available, 2=required)");
 
 module_param_named(guc_log_level, i915.guc_log_level, int, 0400);
 MODULE_PARM_DESC(guc_log_level,
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 02bc278..9f1d17b 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -45,6 +45,8 @@ struct i915_params {
 	int enable_ips;
 	int invert_brightness;
 	int enable_cmd_parser;
+	int enable_guc_loading;
+	int enable_guc_submission;
 	int guc_log_level;
 	int use_mmio_flip;
 	int mmio_debug;
@@ -57,7 +59,6 @@ struct i915_params {
 	bool load_detect_test;
 	bool reset;
 	bool disable_display;
-	bool enable_guc_submission;
 	bool verbose_state_checks;
 	bool nuclear_pageflip;
 	bool enable_dp_mst;
diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
index 876e5da..2ec9cf1 100644
--- a/drivers/gpu/drm/i915/intel_guc_loader.c
+++ b/drivers/gpu/drm/i915/intel_guc_loader.c
@@ -387,49 +387,37 @@ int intel_guc_ucode_load(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
+	const char *fw_path = guc_fw->guc_fw_path;
 	int retries, err = 0;
 
-	if (!i915.enable_guc_submission)
-		return 0;
-
-	DRM_DEBUG_DRIVER("GuC fw status: fetch %s, load %s\n",
+	DRM_DEBUG_DRIVER("GuC fw status: path %s, fetch %s, load %s\n",
+		fw_path,
 		intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
 		intel_guc_fw_status_repr(guc_fw->guc_fw_load_status));
 
-	direct_interrupts_to_host(dev_priv);
+	/* Loading forbidden, or no firmware to load? */
+	if (!i915.enable_guc_loading)
+		goto fail;
+	if (fw_path == NULL)
+		goto fail;
+	if (*fw_path == '\0') {
+		DRM_ERROR("No GuC firmware known for this platform\n");
+		goto fail;
+	}
 
-	if (guc_fw->guc_fw_fetch_status == GUC_FIRMWARE_NONE)
-		return 0;
+	/* Fetch failed, or already fetched but failed to load? */
+	if (guc_fw->guc_fw_fetch_status != GUC_FIRMWARE_SUCCESS)
+		goto fail;
+	if (guc_fw->guc_fw_load_status == GUC_FIRMWARE_FAIL)
+		goto fail;
 
-	if (guc_fw->guc_fw_fetch_status == GUC_FIRMWARE_SUCCESS &&
-	    guc_fw->guc_fw_load_status == GUC_FIRMWARE_FAIL)
-		return -ENOEXEC;
+	direct_interrupts_to_host(dev_priv);
 
 	guc_fw->guc_fw_load_status = GUC_FIRMWARE_PENDING;
 
-	DRM_DEBUG_DRIVER("GuC fw fetch status %s\n",
-		intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status));
-
-	switch (guc_fw->guc_fw_fetch_status) {
-	case GUC_FIRMWARE_FAIL:
-		/* something went wrong :( */
-		err = -EIO;
-		goto fail;
-
-	case GUC_FIRMWARE_NONE:
-	case GUC_FIRMWARE_PENDING:
-	default:
-		/* "can't happen" */
-		WARN_ONCE(1, "GuC fw %s invalid guc_fw_fetch_status %s [%d]\n",
-			guc_fw->guc_fw_path,
-			intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
-			guc_fw->guc_fw_fetch_status);
-		err = -ENXIO;
-		goto fail;
-
-	case GUC_FIRMWARE_SUCCESS:
-		break;
-	}
+	DRM_DEBUG_DRIVER("GuC fw status: fetch %s, load %s\n",
+		intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
+		intel_guc_fw_status_repr(guc_fw->guc_fw_load_status));
 
 	err = i915_guc_submission_init(dev);
 	if (err)
@@ -483,6 +471,7 @@ int intel_guc_ucode_load(struct drm_device *dev)
 
 fail:
 	DRM_ERROR("GuC firmware load failed, err %d\n", err);
+
 	if (guc_fw->guc_fw_load_status == GUC_FIRMWARE_PENDING)
 		guc_fw->guc_fw_load_status = GUC_FIRMWARE_FAIL;
 
@@ -490,6 +479,29 @@ int intel_guc_ucode_load(struct drm_device *dev)
 	i915_guc_submission_disable(dev);
 	i915_guc_submission_fini(dev);
 
+	/*
+	 * We've failed to load the firmware :(
+	 *
+	 * Decide whether to disable GuC submission and fall back to
+	 * execlist mode, and whether to hide the error by returning
+	 * zero or to return -EIO, which the caller will treat as a
+	 * nonfatal error (i.e. it doesn't prevent driver load, but
+	 * marks the GPU as wedged until reset).
+	 */
+	if (i915.enable_guc_loading > 1) {
+		err = -EIO;
+	} else if (HAS_GUC_SCHED(dev) && !HAS_GUC_UCODE(dev)) {
+		return 0;
+	} else if (i915.enable_guc_submission > 1) {
+		err = -EIO;
+	} else {
+		err = 0;
+	}
+
+	i915.enable_guc_submission = 0;
+
+	DRM_DEBUG_DRIVER("falling back to execlist mode, err %d\n", err);
+
 	return err;
 }
 
@@ -631,8 +643,11 @@ void intel_guc_ucode_init(struct drm_device *dev)
 	struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
 	const char *fw_path;
 
-	if (!HAS_GUC_SCHED(dev))
-		i915.enable_guc_submission = false;
+	/* A negative value means "use platform default" */
+	if (i915.enable_guc_loading < 0)
+		i915.enable_guc_loading = HAS_GUC_UCODE(dev);
+	if (i915.enable_guc_submission < 0)
+		i915.enable_guc_submission = HAS_GUC_SCHED(dev);
 
 	if (!HAS_GUC_UCODE(dev)) {
 		fw_path = NULL;
@@ -641,26 +656,21 @@ void intel_guc_ucode_init(struct drm_device *dev)
 		guc_fw->guc_fw_major_wanted = 6;
 		guc_fw->guc_fw_minor_wanted = 1;
 	} else {
-		i915.enable_guc_submission = false;
 		fw_path = "";	/* unknown device */
 	}
 
-	if (!i915.enable_guc_submission)
-		return;
-
 	guc_fw->guc_dev = dev;
 	guc_fw->guc_fw_path = fw_path;
 	guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_NONE;
 	guc_fw->guc_fw_load_status = GUC_FIRMWARE_NONE;
 
+	/* Early (and silent) return if GuC loading is disabled */
+	if (!i915.enable_guc_loading)
+		return;
 	if (fw_path == NULL)
 		return;
-
-	if (*fw_path == '\0') {
-		DRM_ERROR("No GuC firmware known for this platform\n");
-		guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_FAIL;
+	if (*fw_path == '\0')
 		return;
-	}
 
 	guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_PENDING;
 	DRM_DEBUG_DRIVER("GuC firmware pending, path %s\n", fw_path);
-- 
1.9.1

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