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

From: Tomasz Nowicki
Date: Wed Jun 22 2016 - 09:54:00 EST

On 22.06.2016 15:25, Marc Zyngier wrote:
On 22/06/16 13:35, Tomasz Nowicki wrote:
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@xxxxxxxxxxxx>
---
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@xxxxxxxxxxxx>
+ *
+ * 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);

Why did you change this to a naked kfree? The ACPI code clearly states:

/*
* Allocate a new buffer. We directectly call acpi_os_allocate here to
* purposefully bypass the (optionally enabled) internal allocation
* tracking mechanism since we only want to track internal
* allocations. Note: The caller should use acpi_os_free to free this
* buffer created via ACPI_ALLOCATE_BUFFER.
*/

Yes we should use symmetric free function to acpi_os_allocate here, which means acpi_os_free should be used here.

My main motivation was to free buffer.pointer instead of &buffer

Would you mind to fix that (s/kfree/acpi_os_free) before merging ?

Thanks,
Tomasz