drm/i915/huc: Prepare for GSC-loaded HuC

HuC loading via GSC is performed via a PXP command sent through the mei
modules, so we need both MEI_GSC and MEI_PXP to be available. Given that
the GSC will do both the transfer and the authentication, the legacy HuC
loading paths can be safely skipped.
Also note that the GSC-loaded HuC survives GT reset.

v2: move the huc_is_authenticated() function to this patch.
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220504204816.2082588-4-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_reg.h

@@ -96,6 +96,7 @@
 
 #define GUC_SHIM_CONTROL2		_MMIO(0xc068)
 #define   GUC_IS_PRIVILEGED		(1<<29)
+#define   GSC_LOADS_HUC			(1<<30)
 
 #define GUC_SEND_INTERRUPT		_MMIO(0xc4c8)
 #define   GUC_SEND_TRIGGER		  (1<<0)

drivers/gpu/drm/i915/gt/uc/intel_huc.c

@@ -6,6 +6,7 @@
 #include <linux/types.h>
 
 #include "gt/intel_gt.h"
+#include "intel_guc_reg.h"
 #include "intel_huc.h"
 #include "i915_drv.h"
 
@@ -17,11 +18,15 @@
  * capabilities by adding HuC specific commands to batch buffers.
  *
  * The kernel driver is only responsible for loading the HuC firmware and
- * triggering its security authentication, which is performed by the GuC. For
- * The GuC to correctly perform the authentication, the HuC binary must be
- * loaded before the GuC one. Loading the HuC is optional; however, not using
- * the HuC might negatively impact power usage and/or performance of media
- * workloads, depending on the use-cases.
+ * triggering its security authentication, which is performed by the GuC on
+ * older platforms and by the GSC on newer ones. For the GuC to correctly
+ * perform the authentication, the HuC binary must be loaded before the GuC one.
+ * Loading the HuC is optional; however, not using the HuC might negatively
+ * impact power usage and/or performance of media workloads, depending on the
+ * use-cases.
+ * HuC must be reloaded on events that cause the WOPCM to lose its contents
+ * (S3/S4, FLR); GuC-authenticated HuC must also be reloaded on GuC/GT reset,
+ * while GSC-managed HuC will survive that.
  *
  * See https://github.com/intel/media-driver for the latest details on HuC
  * functionality.
@@ -54,11 +59,51 @@ void intel_huc_init_early(struct intel_huc *huc)
 	}
 }
 
+#define HUC_LOAD_MODE_STRING(x) (x ? "GSC" : "legacy")
+static int check_huc_loading_mode(struct intel_huc *huc)
+{
+	struct intel_gt *gt = huc_to_gt(huc);
+	bool fw_needs_gsc = intel_huc_is_loaded_by_gsc(huc);
+	bool hw_uses_gsc = false;
+
+	/*
+	 * The fuse for HuC load via GSC is only valid on platforms that have
+	 * GuC deprivilege.
+	 */
+	if (HAS_GUC_DEPRIVILEGE(gt->i915))
+		hw_uses_gsc = intel_uncore_read(gt->uncore, GUC_SHIM_CONTROL2) &
+			      GSC_LOADS_HUC;
+
+	if (fw_needs_gsc != hw_uses_gsc) {
+		drm_err(&gt->i915->drm,
+			"mismatch between HuC FW (%s) and HW (%s) load modes\n",
+			HUC_LOAD_MODE_STRING(fw_needs_gsc),
+			HUC_LOAD_MODE_STRING(hw_uses_gsc));
+		return -ENOEXEC;
+	}
+
+	/* make sure we can access the GSC via the mei driver if we need it */
+	if (!(IS_ENABLED(CONFIG_INTEL_MEI_PXP) && IS_ENABLED(CONFIG_INTEL_MEI_GSC)) &&
+	    fw_needs_gsc) {
+		drm_info(&gt->i915->drm,
+			 "Can't load HuC due to missing MEI modules\n");
+		return -EIO;
+	}
+
+	drm_dbg(&gt->i915->drm, "GSC loads huc=%s\n", str_yes_no(fw_needs_gsc));
+
+	return 0;
+}
+
 int intel_huc_init(struct intel_huc *huc)
 {
 	struct drm_i915_private *i915 = huc_to_gt(huc)->i915;
 	int err;
 
+	err = check_huc_loading_mode(huc);
+	if (err)
+		goto out;
+
 	err = intel_uc_fw_init(&huc->fw);
 	if (err)
 		goto out;
@@ -96,17 +141,20 @@ int intel_huc_auth(struct intel_huc *huc)
 	struct intel_guc *guc = &gt->uc.guc;
 	int ret;
 
-	GEM_BUG_ON(intel_uc_fw_is_running(&huc->fw));
-
 	if (!intel_uc_fw_is_loaded(&huc->fw))
 		return -ENOEXEC;
 
+	/* GSC will do the auth */
+	if (intel_huc_is_loaded_by_gsc(huc))
+		return -ENODEV;
+
 	ret = i915_inject_probe_error(gt->i915, -ENXIO);
 	if (ret)
 		goto fail;
 
-	ret = intel_guc_auth_huc(guc,
-				 intel_guc_ggtt_offset(guc, huc->fw.rsa_data));
+	GEM_BUG_ON(intel_uc_fw_is_running(&huc->fw));
+
+	ret = intel_guc_auth_huc(guc, intel_guc_ggtt_offset(guc, huc->fw.rsa_data));
 	if (ret) {
 		DRM_ERROR("HuC: GuC did not ack Auth request %d\n", ret);
 		goto fail;
@@ -133,6 +181,18 @@ int intel_huc_auth(struct intel_huc *huc)
 	return ret;
 }
 
+static bool huc_is_authenticated(struct intel_huc *huc)
+{
+	struct intel_gt *gt = huc_to_gt(huc);
+	intel_wakeref_t wakeref;
+	u32 status = 0;
+
+	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
+		status = intel_uncore_read(gt->uncore, huc->status.reg);
+
+	return (status & huc->status.mask) == huc->status.value;
+}
+
 /**
  * intel_huc_check_status() - check HuC status
  * @huc: intel_huc structure
@@ -150,10 +210,6 @@ int intel_huc_auth(struct intel_huc *huc)
  */
 int intel_huc_check_status(struct intel_huc *huc)
 {
-	struct intel_gt *gt = huc_to_gt(huc);
-	intel_wakeref_t wakeref;
-	u32 status = 0;
-
 	switch (__intel_uc_fw_status(&huc->fw)) {
 	case INTEL_UC_FIRMWARE_NOT_SUPPORTED:
 		return -ENODEV;
@@ -167,10 +223,17 @@ int intel_huc_check_status(struct intel_huc *huc)
 		break;
 	}
 
-	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
-		status = intel_uncore_read(gt->uncore, huc->status.reg);
+	return huc_is_authenticated(huc);
+}
 
-	return (status & huc->status.mask) == huc->status.value;
+void intel_huc_update_auth_status(struct intel_huc *huc)
+{
+	if (!intel_uc_fw_is_loadable(&huc->fw))
+		return;
+
+	if (huc_is_authenticated(huc))
+		intel_uc_fw_change_status(&huc->fw,
+					  INTEL_UC_FIRMWARE_RUNNING);
 }
 
 /**

drivers/gpu/drm/i915/gt/uc/intel_huc.h

@@ -27,6 +27,7 @@ int intel_huc_init(struct intel_huc *huc);
 void intel_huc_fini(struct intel_huc *huc);
 int intel_huc_auth(struct intel_huc *huc);
 int intel_huc_check_status(struct intel_huc *huc);
+void intel_huc_update_auth_status(struct intel_huc *huc);
 
 static inline int intel_huc_sanitize(struct intel_huc *huc)
 {
@@ -50,6 +51,11 @@ static inline bool intel_huc_is_used(struct intel_huc *huc)
 	return intel_uc_fw_is_available(&huc->fw);
 }
 
+static inline bool intel_huc_is_loaded_by_gsc(const struct intel_huc *huc)
+{
+	return huc->fw.loaded_via_gsc;
+}
+
 void intel_huc_load_status(struct intel_huc *huc, struct drm_printer *p);
 
 #endif

drivers/gpu/drm/i915/gt/uc/intel_huc_fw.c

@@ -8,7 +8,7 @@
 #include "i915_drv.h"
 
 /**
- * intel_huc_fw_upload() - load HuC uCode to device
+ * intel_huc_fw_upload() - load HuC uCode to device via DMA transfer
  * @huc: intel_huc structure
  *
  * Called from intel_uc_init_hw() during driver load, resume from sleep and
@@ -21,6 +21,9 @@
  */
 int intel_huc_fw_upload(struct intel_huc *huc)
 {
+	if (intel_huc_is_loaded_by_gsc(huc))
+		return -ENODEV;
+
 	/* HW doesn't look at destination address for HuC, so set it to 0 */
 	return intel_uc_fw_upload(&huc->fw, 0, HUC_UKERNEL);
 }

drivers/gpu/drm/i915/gt/uc/intel_uc.c

@@ -509,6 +509,15 @@ static int __uc_init_hw(struct intel_uc *uc)
 	if (ret)
 		goto err_log_capture;
 
+	/*
+	 * GSC-loaded HuC is authenticated by the GSC, so we don't need to
+	 * trigger the auth here. However, given that the HuC loaded this way
+	 * survive GT reset, we still need to update our SW bookkeeping to make
+	 * sure it reflects the correct HW status.
+	 */
+	if (intel_huc_is_loaded_by_gsc(huc))
+		intel_huc_update_auth_status(huc);
+	else
 		intel_huc_auth(huc);
 
 	if (intel_uc_uses_guc_submission(uc))