x86: Support platform PIRQ routing

On x86 boards, platform chipset receives up to four different
interrupt signals from PCI devices (INTA/B/C/D), which in turn
will be routed to chipset internal PIRQ lines then routed to
8259 PIC finally if configuring the whole system to work under
the so-called PIC mode (in contrast to symmetric IO mode which
uses IOAPIC).

We add two major APIs to aid this, one for routing PIRQ and the
other one for generating a PIRQ routing table.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/lib/pirq_routing.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2015, Bin Meng <bmeng.cn@gmail.com>
+ *
+ * Part of this file is ported from coreboot src/arch/x86/boot/pirq_routing.c
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <pci.h>
+#include <asm/pci.h>
+#include <asm/pirq_routing.h>
+#include <asm/tables.h>
+
+static bool irq_already_routed[16];
+
+static u8 pirq_get_next_free_irq(u8 *pirq, u16 bitmap)
+{
+	int i, link;
+	u8 irq = 0;
+
+	/* IRQ sharing starts from IRQ#3 */
+	for (i = 3; i < 16; i++) {
+		/* Can we assign this IRQ? */
+		if (!((bitmap >> i) & 1))
+			continue;
+
+		/* We can, now let's assume we can use this IRQ */
+		irq = i;
+
+		/* Have we already routed it? */
+		if (irq_already_routed[irq])
+			continue;
+
+		for (link = 0; link < CONFIG_MAX_PIRQ_LINKS; link++) {
+			if (pirq_check_irq_routed(link, irq)) {
+				irq_already_routed[irq] = true;
+				break;
+			}
+		}
+
+		/* If it's not yet routed, use it */
+		if (!irq_already_routed[irq]) {
+			irq_already_routed[irq] = true;
+			break;
+		}
+
+		/* But if it was already routed, try the next one */
+	}
+
+	/* Now we get our IRQ */
+	return irq;
+}
+
+void pirq_route_irqs(struct irq_info *irq, int num)
+{
+	unsigned char irq_slot[MAX_INTX_ENTRIES];
+	unsigned char pirq[CONFIG_MAX_PIRQ_LINKS];
+	int i, intx;
+
+	memset(pirq, 0, CONFIG_MAX_PIRQ_LINKS);
+
+	/* Set PCI IRQs */
+	for (i = 0; i < num; i++) {
+		debug("PIRQ Entry %d Dev: %d.%x.%d\n", i,
+		      irq->bus, irq->devfn >> 3, irq->devfn & 7);
+
+		for (intx = 0; intx < MAX_INTX_ENTRIES; intx++) {
+			int link = irq->irq[intx].link;
+			int bitmap = irq->irq[intx].bitmap;
+			int irq = 0;
+
+			debug("INT%c link: %x bitmap: %x ",
+			      'A' + intx, link, bitmap);
+
+			if (!bitmap || !link) {
+				debug("not routed\n");
+				irq_slot[intx] = irq;
+				continue;
+			}
+
+			/* translate link value to link number */
+			link = pirq_translate_link(link);
+
+			/* yet not routed */
+			if (!pirq[link]) {
+				irq = pirq_get_next_free_irq(pirq, bitmap);
+				pirq[link] = irq;
+			} else {
+				irq = pirq[link];
+			}
+
+			debug("IRQ: %d\n", irq);
+			irq_slot[intx] = irq;
+
+			/* Assign IRQ in the interrupt router */
+			pirq_assign_irq(link, irq);
+		}
+
+		/* Bus, device, slots IRQs for {A,B,C,D} */
+		pci_assign_irqs(irq->bus, irq->devfn >> 3, irq->devfn & 7,
+				irq_slot);
+
+		irq++;
+	}
+
+	for (i = 0; i < CONFIG_MAX_PIRQ_LINKS; i++)
+		debug("PIRQ%c: %d\n", 'A' + i, pirq[i]);
+}
+
+u32 copy_pirq_routing_table(u32 addr, struct irq_routing_table *rt)
+{
+	if (rt->signature != PIRQ_SIGNATURE || rt->version != PIRQ_VERSION ||
+	    rt->size % 16) {
+		debug("Interrupt Routing Table not valid\n");
+		return addr;
+	}
+
+	/* Fix up the table checksum */
+	rt->checksum = table_compute_checksum(rt, rt->size);
+
+	/* Align the table to be 16 byte aligned */
+	addr = ALIGN(addr, 16);
+
+	debug("Copying Interrupt Routing Table to 0x%x\n", addr);
+	memcpy((void *)addr, rt, rt->size);
+
+	return addr + rt->size;
+}