soc/intel/common/irq: Add function to return IRQ for PCI devfn

The IRQ for a single device may be required elsewhere, therefore provide
get_pci_devfn_irq.

BUG=b:130217151, b:171580862, b:176858827

Change-Id: Ibebd821767a2698c9e60b09eeeff3bb596359728
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55826
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/block/include/intelblocks/irq.h

@@ -7,6 +7,7 @@
 #include <types.h>
 
 #define MAX_FNS		8
+#define INVALID_IRQ	-1
 
 #define ANY_PIRQ(x)			[PCI_FUNC(x)] = { .fixed_int_pin = PCI_INT_NONE,\
 							  .fixed_pirq = PIRQ_INVALID,	\
@@ -61,4 +62,8 @@ bool irq_program_non_pch(void);
 
 const struct pci_irq_entry *get_cached_pci_irqs(void);
 
+/* Search the cached PCI IRQ assignment results for the matching devfn and
+   return the corresponding IRQ, or INVALID_IRQ if not found. */
+int get_pci_devfn_irq(unsigned int devfn);
+
 #endif /* SOC_INTEL_COMMON_IRQ_H */

src/soc/intel/common/block/irq/irq.c

@@ -21,7 +21,6 @@
 
 #define IDX2PIN(i)		(enum pci_pin)((i) + PCI_INT_A)
 #define PIN2IDX(p)		(size_t)((p) - PCI_INT_A)
-#define INVALID_IRQ		-1
 
 struct pin_info {
 	enum pin_state {
@@ -429,3 +428,17 @@ bool irq_program_non_pch(void)
 
 	return true;
 }
+
+int get_pci_devfn_irq(unsigned int devfn)
+{
+	const struct pci_irq_entry *entry = cached_entries;
+
+	while (entry) {
+		if (entry->devfn == devfn)
+			return entry->irq;
+
+		entry = entry->next;
+	}
+
+	return INVALID_IRQ;
+}