soc/amd/common/fsp/pci: Add helper methods for PCI IRQ table

These are helper methods for interacting with the
AMD_FSP_PCIE_DEVFUNC_REMAP_HOB_GUID.

BUG=b:184766519, b:184766197
TEST=Build guybrush

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Id03d0b74ca12e7bcee11f8d13b0e802861c13923
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52911
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/soc/amd/common/fsp/pci/Kconfig

@@ -0,0 +1,5 @@
+config SOC_AMD_COMMON_FSP_PCI
+	bool
+	select SOC_AMD_COMMON_BLOCK_PCI
+	help
+	  This option enabled FSP to provide common PCI functions.

src/soc/amd/common/fsp/pci/Makefile.inc

@@ -0,0 +1,5 @@
+ifeq ($(CONFIG_SOC_AMD_COMMON_FSP_PCI),y)
+
+ramstage-y += pci_routing_info.c
+
+endif # CONFIG_SOC_AMD_COMMON_FSP_PCI

src/soc/amd/common/fsp/pci/pci_routing_info.c

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <amdblocks/amd_pci_util.h>
+#include <console/console.h>
+#include <device/pci_def.h>
+#include <fsp/util.h>
+#include <FspGuids.h>
+#include <types.h>
+
+const struct pci_routing_info *get_pci_routing_table(size_t *entries)
+{
+	static const struct pci_routing_info *routing_table;
+	static size_t routing_table_entries;
+
+	size_t hob_size = 0;
+
+	if (routing_table) {
+		*entries = routing_table_entries;
+		return routing_table;
+	}
+
+	routing_table = fsp_find_extension_hob_by_guid(AMD_FSP_PCIE_DEVFUNC_REMAP_HOB_GUID.b,
+						       &hob_size);
+
+	if (routing_table == NULL || hob_size == 0) {
+		printk(BIOS_ERR, "Couldn't find PCIe routing HOB.\n");
+		return NULL;
+	}
+
+	routing_table_entries = hob_size / sizeof(struct pci_routing_info);
+
+	for (size_t i = 0; i < routing_table_entries; ++i) {
+		printk(BIOS_DEBUG, "%02x.%x: group: %u, swizzle: %u, irq: %u\n",
+		       PCI_SLOT(routing_table[i].devfn), PCI_FUNC(routing_table[i].devfn),
+		       routing_table[i].group, routing_table[i].swizzle, routing_table[i].irq);
+	}
+
+	*entries = routing_table_entries;
+
+	return routing_table;
+}