PCI/ACPI: Add generic MCFG table handling

On ACPI systems that support memory-mapped config space access, i.e., ECAM,
the PCI Firmware Specification says the OS can learn where the ECAM space
is from either:

  - the static MCFG table (for non-hotpluggable bridges), or
  - the _CBA method (for hotpluggable bridges)

The current MCFG table handling code cannot be easily generalized owing to
x86-specific quirks, which makes it hard to reuse on other architectures.

Implement generic MCFG handling from scratch, including:

  - Simple MCFG table parsing (via pci_mmcfg_late_init() as in current x86)
  - MCFG region lookup for a (domain, bus_start, bus_end) tuple

[bhelgaas: changelog]
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

3 files changed, 96 insertions, 0 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index b7e2e776397d..f98c3287256e 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -217,6 +217,9 @@ config ACPI_PROCESSOR_IDLE
 	bool
 	select CPU_IDLE
 
+config ACPI_MCFG
+	bool
+
 config ACPI_CPPC_LIB
 	bool
 	depends on ACPI_PROCESSOR
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 251ce85a66fb..632e81feef69 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -40,6 +40,7 @@ acpi-$(CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC) += processor_pdc.o
 acpi-y				+= ec.o
 acpi-$(CONFIG_ACPI_DOCK)	+= dock.o
 acpi-y				+= pci_root.o pci_link.o pci_irq.o
+obj-$(CONFIG_ACPI_MCFG)		+= pci_mcfg.o
 acpi-y				+= acpi_lpss.o acpi_apd.o
 acpi-y				+= acpi_platform.o
 acpi-y				+= acpi_pnp.o
diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
new file mode 100644
index 000000000000..b5b376e081f5
--- /dev/null
+++ b/drivers/acpi/pci_mcfg.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2016 Broadcom
+ *	Author: Jayachandran C <jchandra@broadcom.com>
+ * Copyright (C) 2016 Semihalf
+ * 	Author: Tomasz Nowicki <tn@semihalf.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation (the "GPL").
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License version 2 (GPLv2) for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 (GPLv2) along with this source code.
+ */
+
+#define pr_fmt(fmt) "ACPI: " fmt
+
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/pci-acpi.h>
+
+/* Structure to hold entries from the MCFG table */
+struct mcfg_entry {
+	struct list_head	list;
+	phys_addr_t		addr;
+	u16			segment;
+	u8			bus_start;
+	u8			bus_end;
+};
+
+/* List to save MCFG entries */
+static LIST_HEAD(pci_mcfg_list);
+
+phys_addr_t pci_mcfg_lookup(u16 seg, struct resource *bus_res)
+{
+	struct mcfg_entry *e;
+
+	/*
+	 * We expect exact match, unless MCFG entry end bus covers more than
+	 * specified by caller.
+	 */
+	list_for_each_entry(e, &pci_mcfg_list, list) {
+		if (e->segment == seg && e->bus_start == bus_res->start &&
+		    e->bus_end >= bus_res->end)
+			return e->addr;
+	}
+
+	return 0;
+}
+
+static __init int pci_mcfg_parse(struct acpi_table_header *header)
+{
+	struct acpi_table_mcfg *mcfg;
+	struct acpi_mcfg_allocation *mptr;
+	struct mcfg_entry *e, *arr;
+	int i, n;
+
+	if (header->length < sizeof(struct acpi_table_mcfg))
+		return -EINVAL;
+
+	n = (header->length - sizeof(struct acpi_table_mcfg)) /
+					sizeof(struct acpi_mcfg_allocation);
+	mcfg = (struct acpi_table_mcfg *)header;
+	mptr = (struct acpi_mcfg_allocation *) &mcfg[1];
+
+	arr = kcalloc(n, sizeof(*arr), GFP_KERNEL);
+	if (!arr)
+		return -ENOMEM;
+
+	for (i = 0, e = arr; i < n; i++, mptr++, e++) {
+		e->segment = mptr->pci_segment;
+		e->addr =  mptr->address;
+		e->bus_start = mptr->start_bus_number;
+		e->bus_end = mptr->end_bus_number;
+		list_add(&e->list, &pci_mcfg_list);
+	}
+
+	pr_info("MCFG table detected, %d entries\n", n);
+	return 0;
+}
+
+/* Interface called by ACPI - parse and save MCFG table */
+void __init pci_mmcfg_late_init(void)
+{
+	int err = acpi_table_parse(ACPI_SIG_MCFG, pci_mcfg_parse);
+	if (err)
+		pr_err("Failed to parse MCFG (%d)\n", err);
+}