3 files changed, 85 insertions, 0 deletions
diff --git a/src/soc/amd/common/block/include/amdblocks/amd_pci_util.h b/src/soc/amd/common/block/include/amdblocks/amd_pci_util.h
index 081741ad28..b9cd1406c9 100644
--- a/src/soc/amd/common/block/include/amdblocks/amd_pci_util.h
+++ b/src/soc/amd/common/block/include/amdblocks/amd_pci_util.h
@@ -31,7 +31,34 @@ void write_pci_cfg_irqs(void);
 void write_pci_int_table(void);
 const struct irq_idx_name *sb_get_apic_reg_association(size_t *size);
 
+enum pci_routing_swizzle {
+	PCI_SWIZZLE_ABCD = 0,
+	PCI_SWIZZLE_BCDA,
+	PCI_SWIZZLE_CDAB,
+	PCI_SWIZZLE_DABC,
+};
+
+/**
+ * Each PCI bridge has its INTx lines routed to one of the GNB IO-APIC PCI
+ * groups. Each group has 4 interrupts. The INTx lines can be swizzled before
+ * being routed to the IO-APIC. If the IO-APIC redirection entry is masked, the
+ * interrupt is reduced modulo 8 onto INT[A-H] and forwarded to the FCH IO-APIC.
+ **/
+struct pci_routing_info {
+	uint8_t devfn;
+	uint8_t group;
+	uint8_t swizzle;
+	uint8_t irq;
+} __packed;
+
 /* Implemented by the SoC */
 void populate_pirq_data(void);
 
+/* Implemented by the SoC */
+const struct pci_routing_info *get_pci_routing_table(size_t *entries);
+
+const struct pci_routing_info *get_pci_routing_info(unsigned int devfn);
+
+unsigned int pci_calculate_irq(const struct pci_routing_info *routing_info, unsigned int pin);
+
 #endif /* AMD_BLOCK_PCI_UTIL_H */
diff --git a/src/soc/amd/common/block/pci/Makefile.inc b/src/soc/amd/common/block/pci/Makefile.inc
index 78453d464f..5df641b1d9 100644
--- a/src/soc/amd/common/block/pci/Makefile.inc
+++ b/src/soc/amd/common/block/pci/Makefile.inc
@@ -1,4 +1,5 @@
 ramstage-$(CONFIG_SOC_AMD_COMMON_BLOCK_PCI) += amd_pci_util.c
+ramstage-$(CONFIG_SOC_AMD_COMMON_BLOCK_PCI) += pci_routing_info.c
 
 ifeq ($(CONFIG_SOC_AMD_COMMON_BLOCK_PCI_MMCONF),y)
 
diff --git a/src/soc/amd/common/block/pci/pci_routing_info.c b/src/soc/amd/common/block/pci/pci_routing_info.c
new file mode 100644
index 0000000000..e0a696442e
--- /dev/null
+++ b/src/soc/amd/common/block/pci/pci_routing_info.c
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <amdblocks/amd_pci_util.h>
+#include <console/console.h>
+#include <device/pci_def.h>
+#include <types.h>
+
+enum pcie_swizzle_pin {
+	PIN_A,
+	PIN_B,
+	PIN_C,
+	PIN_D,
+};
+
+static const uint8_t pcie_swizzle_table[][4] = {
+	{PIN_A, PIN_B, PIN_C, PIN_D},
+	{PIN_B, PIN_C, PIN_D, PIN_A},
+	{PIN_C, PIN_D, PIN_A, PIN_B},
+	{PIN_D, PIN_A, PIN_B, PIN_C},
+};
+
+const struct pci_routing_info *get_pci_routing_info(unsigned int devfn)
+{
+	const struct pci_routing_info *routing_info;
+	size_t entries = 0;
+
+	routing_info = get_pci_routing_table(&entries);
+
+	if (!routing_info || !entries)
+		return NULL;
+
+	for (size_t i = 0; i < entries; ++i, ++routing_info)
+		if (routing_info->devfn == devfn)
+			return routing_info;
+
+	printk(BIOS_ERR, "Failed to find PCIe routing info for dev: %#x, fn: %#x\n",
+	       PCI_SLOT(devfn), PCI_FUNC(devfn));
+
+	return NULL;
+}
+
+unsigned int pci_calculate_irq(const struct pci_routing_info *routing_info,
+					      unsigned int pin)
+{
+	unsigned int irq;
+
+	if (routing_info->swizzle >= ARRAY_SIZE(pcie_swizzle_table))
+		die("%s: swizzle %u out of bounds\n", __func__, routing_info->swizzle);
+
+	if (pin >= ARRAY_SIZE(pcie_swizzle_table[routing_info->swizzle]))
+		die("%s: pin %u out of bounds\n", __func__, pin);
+
+	irq = routing_info->group * 4;
+	irq += pcie_swizzle_table[routing_info->swizzle][pin];
+
+	return irq;
+}