drm/i915/huc: Load GSC-enabled HuC via DMA xfer if the fuse says so

In the previous patch we extracted the offset of the legacy-style HuC
binary located within the GSC-enabled blob, so now we can use that to
load the HuC via DMA if the fuse is set that way.
Note that we now need to differentiate between "GSC-enabled binary" and
"loaded by GSC", so the former case has been renamed to "has GSC headers"
for clarity, while the latter is now based on the fuse instead of the
binary format. This way, all the legacy load paths are automatically
taken (including the auth by GuC) without having to implement further
code changes.

v2: s/is_meu_binary/has_gsc_headers/, clearer logs (John)

v3: split check for GSC access, better comments (John)
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230531235415.1467475-4-daniele.ceraolospurio@intel.com

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

@@ -298,31 +298,54 @@ void intel_huc_init_early(struct intel_huc *huc)
 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;
+	bool gsc_enabled = huc->fw.has_gsc_headers;
 
 	/*
 	 * 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;
+		huc->loaded_via_gsc = intel_uncore_read(gt->uncore, GUC_SHIM_CONTROL2) &
+				      GSC_LOADS_HUC;
 
-	if (fw_needs_gsc != hw_uses_gsc) {
-		huc_err(huc, "mismatch between FW (%s) and HW (%s) load modes\n",
-			HUC_LOAD_MODE_STRING(fw_needs_gsc), HUC_LOAD_MODE_STRING(hw_uses_gsc));
+	if (huc->loaded_via_gsc && !gsc_enabled) {
+		huc_err(huc, "HW requires a GSC-enabled blob, but we found a legacy one\n");
 		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) {
-		huc_info(huc, "can't load due to missing MEI modules\n");
-		return -EIO;
+	/*
+	 * On newer platforms we have GSC-enabled binaries but we load the HuC
+	 * via DMA. To do so we need to find the location of the legacy-style
+	 * binary inside the GSC-enabled one, which we do at fetch time. Make
+	 * sure that we were able to do so if the fuse says we need to load via
+	 * DMA and the binary is GSC-enabled.
+	 */
+	if (!huc->loaded_via_gsc && gsc_enabled && !huc->fw.dma_start_offset) {
+		huc_err(huc, "HW in DMA mode, but we have an incompatible GSC-enabled blob\n");
+		return -ENOEXEC;
+	}
+
+	/*
+	 * If the HuC is loaded via GSC, we need to be able to access the GSC.
+	 * On DG2 this is done via the mei components, while on newer platforms
+	 * it is done via the GSCCS,
+	 */
+	if (huc->loaded_via_gsc) {
+		if (IS_DG2(gt->i915)) {
+			if (!IS_ENABLED(CONFIG_INTEL_MEI_PXP) ||
+			    !IS_ENABLED(CONFIG_INTEL_MEI_GSC)) {
+				huc_info(huc, "can't load due to missing mei modules\n");
+				return -EIO;
+			}
+		} else {
+			if (!HAS_ENGINE(gt, GSC0)) {
+				huc_info(huc, "can't load due to missing GSCCS\n");
+				return -EIO;
+			}
+		}
 	}
 
-	huc_dbg(huc, "loaded by GSC = %s\n", str_yes_no(fw_needs_gsc));
+	huc_dbg(huc, "loaded by GSC = %s\n", str_yes_no(huc->loaded_via_gsc));
 
 	return 0;
 }

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

@@ -39,6 +39,8 @@ struct intel_huc {
 		struct notifier_block nb;
 		enum intel_huc_delayed_load_status status;
 	} delayed_load;
+
+	bool loaded_via_gsc;
 };
 
 int intel_huc_sanitize(struct intel_huc *huc);
@@ -73,7 +75,7 @@ static inline bool intel_huc_is_used(struct intel_huc *huc)
 
 static inline bool intel_huc_is_loaded_by_gsc(const struct intel_huc *huc)
 {
-	return huc->fw.loaded_via_gsc;
+	return huc->loaded_via_gsc;
 }
 
 static inline bool intel_huc_wait_required(struct intel_huc *huc)

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

@@ -50,7 +50,7 @@ int intel_huc_fw_get_binary_info(struct intel_uc_fw *huc_fw, const void *data, s
 	size_t min_size = sizeof(*header);
 	int i;
 
-	if (!huc_fw->loaded_via_gsc) {
+	if (!huc_fw->has_gsc_headers) {
 		huc_err(huc, "Invalid FW type for GSC header parsing!\n");
 		return -EINVAL;
 	}

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

@@ -186,7 +186,7 @@ struct __packed uc_fw_blob {
 	u8 major;
 	u8 minor;
 	u8 patch;
-	bool loaded_via_gsc;
+	bool has_gsc_headers;
 };
 
 #define UC_FW_BLOB_BASE(major_, minor_, patch_, path_) \
@@ -197,7 +197,7 @@ struct __packed uc_fw_blob {
 
 #define UC_FW_BLOB_NEW(major_, minor_, patch_, gsc_, path_) \
 	{ UC_FW_BLOB_BASE(major_, minor_, patch_, path_) \
-	  .legacy = false, .loaded_via_gsc = gsc_ }
+	  .legacy = false, .has_gsc_headers = gsc_ }
 
 #define UC_FW_BLOB_OLD(major_, minor_, patch_, path_) \
 	{ UC_FW_BLOB_BASE(major_, minor_, patch_, path_) \
@@ -310,7 +310,7 @@ __uc_fw_auto_select(struct drm_i915_private *i915, struct intel_uc_fw *uc_fw)
 		uc_fw->file_wanted.ver.major = blob->major;
 		uc_fw->file_wanted.ver.minor = blob->minor;
 		uc_fw->file_wanted.ver.patch = blob->patch;
-		uc_fw->loaded_via_gsc = blob->loaded_via_gsc;
+		uc_fw->has_gsc_headers = blob->has_gsc_headers;
 		found = true;
 		break;
 	}
@@ -737,7 +737,7 @@ static int check_fw_header(struct intel_gt *gt,
 	if (uc_fw->type == INTEL_UC_FW_TYPE_GSC)
 		return 0;
 
-	if (uc_fw->loaded_via_gsc)
+	if (uc_fw->has_gsc_headers)
 		err = check_gsc_manifest(gt, fw, uc_fw);
 	else
 		err = check_ccs_header(gt, fw, uc_fw);
@@ -999,7 +999,7 @@ static int uc_fw_xfer(struct intel_uc_fw *uc_fw, u32 dst_offset, u32 dma_flags)
 	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
 
 	/* Set the source address for the uCode */
-	offset = uc_fw->vma_res.start;
+	offset = uc_fw->vma_res.start + uc_fw->dma_start_offset;
 	GEM_BUG_ON(upper_32_bits(offset) & 0xFFFF0000);
 	intel_uncore_write_fw(uncore, DMA_ADDR_0_LOW, lower_32_bits(offset));
 	intel_uncore_write_fw(uncore, DMA_ADDR_0_HIGH, upper_32_bits(offset));
@@ -1238,7 +1238,7 @@ size_t intel_uc_fw_copy_rsa(struct intel_uc_fw *uc_fw, void *dst, u32 max_len)
 {
 	struct intel_memory_region *mr = uc_fw->obj->mm.region;
 	u32 size = min_t(u32, uc_fw->rsa_size, max_len);
-	u32 offset = sizeof(struct uc_css_header) + uc_fw->ucode_size;
+	u32 offset = uc_fw->dma_start_offset + sizeof(struct uc_css_header) + uc_fw->ucode_size;
 	struct sgt_iter iter;
 	size_t count = 0;
 	int idx;

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

@@ -120,7 +120,7 @@ struct intel_uc_fw {
 
 	u32 dma_start_offset;
 
-	bool loaded_via_gsc;
+	bool has_gsc_headers;
 };
 
 /*