[PATCH V7 1/8] ACPI: I/O Remapping Table (IORT) initial support

[Tomasz Nowicki <tn@semihalf.com>]

IORT shows representation of IO topology for ARM based systems.
It describes how various components are connected together on
parent-child basis e.g. PCI RC -> SMMU -> ITS. Also see IORT spec.
http://infocenter.arm.com/help/topic/com.arm.doc.den0049b/DEN0049B_IO_Remapping_Table.pdf

Initial support allows to detect IORT table presence and save its
root pointer obtained through acpi_get_table(). The pointer validity
depends on acpi_gbl_permanent_mmap because if acpi_gbl_permanent_mmap
is not set while using IORT nodes we would dereference unmapped pointers.

For the aforementioned reason call iort_table_detect() from acpi_init()
which guarantees acpi_gbl_permanent_mmap to be set at that point.

Add generic helpers which are helpful for scanning and retrieving
information from IORT table content. List of the most important helpers:
- iort_find_dev_node() finds IORT node for a given device
- iort_node_map_rid() maps device RID and returns IORT node which provides
  final translation

Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
---
 drivers/acpi/Kconfig  |   3 +
 drivers/acpi/Makefile |   1 +
 drivers/acpi/bus.c    |   2 +
 drivers/acpi/iort.c   | 217 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/iort.h  |  30 +++++++
 5 files changed, 253 insertions(+)
 create mode 100644 drivers/acpi/iort.c
 create mode 100644 include/linux/iort.h

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index b7e2e77..848471f 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -57,6 +57,9 @@ config ACPI_SYSTEM_POWER_STATES_SUPPORT
 config ACPI_CCA_REQUIRED
 	bool
 
+config IORT_TABLE
+	bool
+
 config ACPI_DEBUGGER
 	bool "AML debugger interface"
 	select ACPI_DEBUG
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 251ce85..c7c9b29 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
 obj-$(CONFIG_ACPI_BGRT)		+= bgrt.o
 obj-$(CONFIG_ACPI_CPPC_LIB)	+= cppc_acpi.o
 obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o
+obj-$(CONFIG_IORT_TABLE) 	+= iort.o
 
 # processor has its own "processor." module_param namespace
 processor-y			:= processor_driver.o
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 31e8da6..176c17d 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -33,6 +33,7 @@
 #ifdef CONFIG_X86
 #include <asm/mpspec.h>
 #endif
+#include <linux/iort.h>
 #include <linux/pci.h>
 #include <acpi/apei.h>
 #include <linux/dmi.h>
@@ -1118,6 +1119,7 @@ static int __init acpi_init(void)
 	}
 
 	pci_mmcfg_late_init();
+	iort_table_detect();
 	acpi_scan_init();
 	acpi_ec_init();
 	acpi_debugfs_init();
diff --git a/drivers/acpi/iort.c b/drivers/acpi/iort.c
new file mode 100644
index 0000000..fcfa008f
--- /dev/null
+++ b/drivers/acpi/iort.c
@@ -0,0 +1,217 @@
+/*
+ * 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 and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 for
+ * more details.
+ *
+ * This file implements early detection/parsing of I/O mapping
+ * reported to OS through firmware via I/O Remapping Table (IORT)
+ * IORT document number: ARM DEN 0049A
+ */
+
+#define pr_fmt(fmt)	"ACPI: IORT: " fmt
+
+#include <linux/iort.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+
+typedef acpi_status (*iort_find_node_callback)
+	(struct acpi_iort_node *node, void *context);
+
+/* Root pointer to the mapped IORT table */
+static struct acpi_table_header *iort_table;
+
+static struct acpi_iort_node *
+iort_scan_node(enum acpi_iort_node_type type,
+	       iort_find_node_callback callback, void *context)
+{
+	struct acpi_iort_node *iort_node, *iort_end;
+	struct acpi_table_iort *iort;
+	int i;
+
+	/* Get the first IORT node */
+	iort = (struct acpi_table_iort *)iort_table;
+	iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort,
+				 iort->node_offset);
+	iort_end = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
+				iort_table->length);
+
+	for (i = 0; i < iort->node_count; i++) {
+		if (WARN_TAINT(iort_node >= iort_end, TAINT_FIRMWARE_WORKAROUND,
+			       "IORT node pointer overflows, bad table!\n"))
+			return NULL;
+
+		if (iort_node->type == type) {
+			if (ACPI_SUCCESS(callback(iort_node, context)))
+				return iort_node;
+		}
+
+		iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
+					 iort_node->length);
+	}
+
+	return NULL;
+}
+
+static acpi_status
+iort_match_node_callback(struct acpi_iort_node *node, void *context)
+{
+	struct device *dev = context;
+
+	switch (node->type) {
+	case ACPI_IORT_NODE_NAMED_COMPONENT: {
+		struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+		struct acpi_device *adev = to_acpi_device_node(dev->fwnode);
+		struct acpi_iort_named_component *ncomp;
+
+		if (!adev)
+			break;
+
+		ncomp = (struct acpi_iort_named_component *)node->node_data;
+
+		if (ACPI_FAILURE(acpi_get_name(adev->handle,
+					       ACPI_FULL_PATHNAME, &buffer))) {
+			dev_warn(dev, "Can't get device full path name\n");
+		} else {
+			int match;
+
+			match = !strcmp(ncomp->device_name, buffer.pointer);
+			kfree(buffer.pointer);
+
+			if (match)
+				return AE_OK;
+		}
+
+		break;
+	}
+	case ACPI_IORT_NODE_PCI_ROOT_COMPLEX: {
+		struct acpi_iort_root_complex *pci_rc;
+		struct pci_bus *bus;
+
+		bus = to_pci_bus(dev);
+		pci_rc = (struct acpi_iort_root_complex *)node->node_data;
+
+		/*
+		 * It is assumed that PCI segment numbers maps one-to-one
+		 * with root complexes. Each segment number can represent only
+		 * one root complex.
+		 */
+		if (pci_rc->pci_segment_number == pci_domain_nr(bus))
+			return AE_OK;
+
+		break;
+	}
+	}
+
+	return AE_NOT_FOUND;
+}
+
+static int
+iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in, u32 *rid_out)
+{
+	/* Single mapping does not care for input id */
+	if (map->flags & ACPI_IORT_ID_SINGLE_MAPPING) {
+		if (type == ACPI_IORT_NODE_NAMED_COMPONENT ||
+		    type == ACPI_IORT_NODE_PCI_ROOT_COMPLEX) {
+			*rid_out = map->output_base;
+			return 0;
+		}
+
+		pr_warn(FW_BUG "[map %p] SINGLE MAPPING flag not allowed for node type %d, skipping ID map\n",
+			map, type);
+		return -ENXIO;
+	}
+
+	if (rid_in < map->input_base ||
+	    (rid_in > map->input_base + map->id_count))
+		return -ENXIO;
+
+	*rid_out = map->output_base + (rid_in - map->input_base);
+	return 0;
+}
+
+static struct acpi_iort_node *
+iort_node_map_rid(struct acpi_iort_node *node, u32 rid_in,
+		  u32 *rid_out, u8 type)
+{
+	u32 rid = rid_in;
+
+	/* Parse the ID mapping tree to find specified node type */
+	while (node) {
+		struct acpi_iort_id_mapping *map;
+		int i;
+
+		if (node->type == type) {
+			if (rid_out)
+				*rid_out = rid;
+			return node;
+		}
+
+		if (!node->mapping_offset || !node->mapping_count)
+			goto fail_map;
+
+		map = ACPI_ADD_PTR(struct acpi_iort_id_mapping, node,
+				  node->mapping_offset);
+
+		/* Firmware bug! */
+		if (!map->output_reference) {
+			pr_err(FW_BUG "[node %p type %d] ID map has NULL parent reference\n",
+			       node, node->type);
+			goto fail_map;
+		}
+
+		/* Do the RID translation */
+		for (i = 0; i < node->mapping_count; i++, map++) {
+			if(!iort_id_map(map, node->type, rid, &rid))
+				break;
+		}
+
+		if (i == node->mapping_count)
+			goto fail_map;
+
+		node = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
+				    map->output_reference);
+	}
+
+fail_map:
+	/* Map input RID to output RID unchanged on mapping failure*/
+	if (rid_out)
+		*rid_out = rid_in;
+	return NULL;
+}
+
+static struct acpi_iort_node *
+iort_find_dev_node(struct device *dev)
+{
+	struct pci_bus *pbus;
+
+	if (!dev_is_pci(dev))
+		return iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
+				      iort_match_node_callback, dev);
+
+	/* Find a PCI root bus */
+	pbus = to_pci_dev(dev)->bus;
+	while (!pci_is_root_bus(pbus))
+		pbus = pbus->parent;
+
+	return iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
+			      iort_match_node_callback, &pbus->dev);
+}
+
+void __init iort_table_detect(void)
+{
+	acpi_status status;
+
+	status = acpi_get_table(ACPI_SIG_IORT, 0, &iort_table);
+	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
+		const char *msg = acpi_format_exception(status);
+		pr_err("Failed to get table, %s\n", msg);
+	}
+}
diff --git a/include/linux/iort.h b/include/linux/iort.h
new file mode 100644
index 0000000..cde6809
--- /dev/null
+++ b/include/linux/iort.h
@@ -0,0 +1,30 @@
+/*
+ * 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 and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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 for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#ifndef __IORT_H__
+#define __IORT_H__
+
+#include <linux/acpi.h>
+
+#ifdef CONFIG_IORT_TABLE
+void iort_table_detect(void);
+#else
+static inline void iort_table_detect(void) { }
+#endif
+
+#endif /* __IORT_H__ */
-- 
1.9.1