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>

4 files changed, 300 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3f1401a..aaceaef 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -442,6 +442,37 @@ config TSC_FREQ_IN_MHZ
 	help
 	  The running frequency in MHz of Time-Stamp Counter (TSC).
 
+menu "System tables"
+
+config GENERATE_PIRQ_TABLE
+	bool "Generate a PIRQ table"
+	default n
+	help
+	  Generate a PIRQ routing table for this board. The PIRQ routing table
+	  is generated by U-Boot in the system memory from 0xf0000 to 0xfffff
+	  at every 16-byte boundary with a PCI IRQ routing signature ("$PIR").
+	  It specifies the interrupt router information as well how all the PCI
+	  devices' interrupt pins are wired to PIRQs.
+
+endmenu
+
+config MAX_PIRQ_LINKS
+	int
+	default 8
+	help
+	  This variable specifies the number of PIRQ interrupt links which are
+	  routable. On most older chipsets, this is 4, PIRQA through PIRQD.
+	  Some newer chipsets offer more than four links, commonly up to PIRQH.
+
+config IRQ_SLOT_COUNT
+	int
+	default 128
+	help
+	  U-Boot can support up to 254 IRQ slot info in the PIRQ routing table
+	  which in turns forms a table of exact 4KiB. The default value 128
+	  should be enough for most boards. If this does not fit your board,
+	  change it according to your needs.
+
 source "board/coreboot/coreboot/Kconfig"
 
 source "board/google/chromebook_link/Kconfig"
diff --git a/arch/x86/include/asm/pirq_routing.h b/arch/x86/include/asm/pirq_routing.h
new file mode 100644
index 0000000..ddc08e1
--- /dev/null
+++ b/arch/x86/include/asm/pirq_routing.h
@@ -0,0 +1,139 @@
+/*
+ * Copyright (C) 2015, Bin Meng <bmeng.cn@gmail.com>
+ *
+ * Ported from coreboot src/arch/x86/include/arch/pirq_routing.h
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _PIRQ_ROUTING_H_
+#define _PIRQ_ROUTING_H_
+
+/*
+ * This is the maximum number on interrupt entries that a PCI device may have.
+ *   This is NOT the number of slots or devices in the system
+ *   This is NOT the number of entries in the PIRQ table
+ *
+ * This tells us that in the PIRQ table, we are going to have 4 link-bitmap
+ * entries per PCI device which is fixed at 4: INTA, INTB, INTC, and INTD.
+ *
+ * CAUTION: If you change this, PIRQ routing will not work correctly.
+ */
+#define MAX_INTX_ENTRIES	4
+
+#define PIRQ_SIGNATURE		\
+	(('$' << 0) + ('P' << 8) + ('I' << 16) + ('R' << 24))
+#define PIRQ_VERSION		0x0100
+
+struct __packed irq_info {
+	u8 bus;			/* Bus number */
+	u8 devfn;		/* Device and function number */
+	struct __packed {
+		u8 link;	/* IRQ line ID, 0=not routed */
+		u16 bitmap;	/* Available IRQs */
+	} irq[MAX_INTX_ENTRIES];
+	u8 slot;		/* Slot number, 0=onboard */
+	u8 rfu;
+};
+
+struct __packed irq_routing_table {
+	u32 signature;		/* PIRQ_SIGNATURE */
+	u16 version;		/* PIRQ_VERSION */
+	u16 size;		/* Table size in bytes */
+	u8 rtr_bus;		/* busno of the interrupt router */
+	u8 rtr_devfn;		/* devfn of the interrupt router */
+	u16 exclusive_irqs;	/* IRQs devoted exclusively to PCI usage */
+	u16 rtr_vendor;		/* Vendor ID of the interrupt router */
+	u16 rtr_device;		/* Device ID of the interrupt router */
+	u32 miniport_data;
+	u8 rfu[11];
+	u8 checksum;		/* Modulo 256 checksum must give zero */
+	struct irq_info slots[CONFIG_IRQ_SLOT_COUNT];
+};
+
+/**
+ * get_irq_slot_count() - Get the number of entries in the irq_info table
+ *
+ * This calculates the number of entries for the irq_info table.
+ *
+ * @rt:		pointer to the base address of the struct irq_info
+ * @return:	number of entries
+ */
+static inline int get_irq_slot_count(struct irq_routing_table *rt)
+{
+	return (rt->size - 32) / sizeof(struct irq_info);
+}
+
+/**
+ * pirq_check_irq_routed() - Check whether an IRQ is routed to 8259 PIC
+ *
+ * This function checks whether an IRQ is routed to 8259 PIC for a given link.
+ *
+ * Note: this function should be provided by the platform codes, as the
+ * implementation of interrupt router may be different.
+ *
+ * @link:	link number which represents a PIRQ
+ * @irq:	the 8259 IRQ number
+ * @return:	true if the irq is already routed to 8259 for a given link,
+ *		false elsewise
+ */
+bool pirq_check_irq_routed(int link, u8 irq);
+
+/**
+ * pirq_translate_link() - Translate a link value
+ *
+ * This function translates a platform-specific link value to a link number.
+ * On Intel platforms, the link value is normally a offset into the PCI
+ * configuration space into the legacy bridge.
+ *
+ * Note: this function should be provided by the platform codes, as the
+ * implementation of interrupt router may be different.
+ *
+ * @link:	platform-specific link value
+ * @return:	link number which represents a PIRQ
+ */
+int pirq_translate_link(int link);
+
+/**
+ * pirq_assign_irq() - Assign an IRQ to a PIRQ link
+ *
+ * This function assigns the IRQ to a PIRQ link so that the PIRQ is routed to
+ * the 8259 PIC.
+ *
+ * Note: this function should be provided by the platform codes, as the
+ * implementation of interrupt router may be different.
+ *
+ * @link:	link number which represents a PIRQ
+ * @irq:	IRQ to which the PIRQ is routed
+ */
+void pirq_assign_irq(int link, u8 irq);
+
+/**
+ * pirq_route_irqs() - Route PIRQs to 8259 PIC
+ *
+ * This function configures all PCI devices' interrupt pins and maps them to
+ * PIRQs and finally 8259 PIC. The routed irq number is written to interrupt
+ * line register in the configuration space of the PCI device for OS to use.
+ * The configuration source is taken from a struct irq_info table, the format
+ * of which is defined in PIRQ routing table spec and PCI BIOS spec.
+ *
+ * @irq:	pointer to the base address of the struct irq_info
+ * @num:	number of entries in the struct irq_info
+ */
+void pirq_route_irqs(struct irq_info *irq, int num);
+
+/**
+ * copy_pirq_routing_table() - Copy a PIRQ routing table
+ *
+ * This helper function copies the given PIRQ routing table to a given address.
+ * Before copying, it does several sanity tests against the PIRQ routing table.
+ * It also fixes up the table checksum and align the given address to a 16 byte
+ * boundary to meet the PIRQ routing table spec requirements.
+ *
+ * @addr:	address to store the copied PIRQ routing table
+ * @rt:		pointer to the PIRQ routing table to copy from
+ * @return:	end address of the copied PIRQ routing table
+ */
+u32 copy_pirq_routing_table(u32 addr, struct irq_routing_table *rt);
+
+#endif /* _PIRQ_ROUTING_H_ */
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 0de0d89..0178fe1 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -22,6 +22,7 @@ ifndef CONFIG_DM_PCI
 obj-$(CONFIG_PCI) += pci_type1.o
 endif
 obj-y	+= pch-uclass.o
+obj-y	+= pirq_routing.o
 obj-y	+= relocate.o
 obj-y += physmem.o
 obj-$(CONFIG_X86_RAMTEST) += ramtest.o
diff --git a/arch/x86/lib/pirq_routing.c b/arch/x86/lib/pirq_routing.c
new file mode 100644
index 0000000..5a2591a
--- /dev/null
+++ b/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;
+}