[PATCH V2 22/23] pci, acpi: Match PCI config space accessors against platfrom specific quirks.

[Tomasz Nowicki]

Some platforms may not be fully compliant with generic set of PCI config
accessors. For these cases we implement the way to overwrite accessors
set before PCI buses enumeration. Algorithm that overwrite accessors
matches against platform ID (DMI), domain and bus number, hopefully
enough for all cases. All quirks can be defined using:
DECLARE_ACPI_MCFG_FIXUP() and keep self contained.

example:

static const struct dmi_system_id yyy[] = {
	{
		.ident = "<Platform ident string>",
		.callback = <handler>,
		.matches = {
			DMI_MATCH(DMI_SYS_VENDOR, "<system vendor>"),
			DMI_MATCH(DMI_PRODUCT_NAME, "<product name>"),
			DMI_MATCH(DMI_PRODUCT_VERSION, "product version"),
		},
	},
	{ }
};

static struct pci_ops ecam_pci_ops = {
	.map_bus = pci_mcfg_dev_base,
	.read = xxxx_ecam_config_read,
	.write = xxxx_ecam_config_write,
};
DECLARE_ACPI_MCFG_FIXUP(yyy, &ecam_pci_ops, <domain_nr>, <bus_nr>);

Note, that more custom actions can be done via DMI callback hook.

Signed-off-by: Tomasz Nowicki <tn at semihalf.com>
---
 drivers/acpi/mcfg.c               | 35 +++++++++++++++++++++++++++++++++--
 include/asm-generic/vmlinux.lds.h |  7 +++++++
 include/linux/ecam.h              | 17 +++++++++++++++++
 3 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/mcfg.c b/drivers/acpi/mcfg.c
index a9b2231..6d0194d 100644
--- a/drivers/acpi/mcfg.c
+++ b/drivers/acpi/mcfg.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/dmi.h>
 #include <linux/ecam.h>
 #include <linux/pci.h>
 #include <linux/pci-acpi.h>
@@ -34,6 +35,31 @@ int __weak raw_pci_write(unsigned int domain, unsigned int bus,
 	return PCIBIOS_DEVICE_NOT_FOUND;
 }
 
+extern struct pci_mcfg_fixup __start_acpi_mcfg_fixups[];
+extern struct pci_mcfg_fixup __end_acpi_mcfg_fixups[];
+
+static struct pci_ops *pci_mcfg_check_quirks(int domain, int bus_number)
+{
+	struct pci_mcfg_fixup *fixup;
+
+	fixup = __start_acpi_mcfg_fixups;
+	while (fixup < __end_acpi_mcfg_fixups) {
+		if (dmi_check_system(fixup->system) &&
+		    (fixup->domain == domain ||
+		     fixup->domain == PCI_MCFG_DOMAIN_ANY) &&
+		    (fixup->bus_number == bus_number ||
+		     fixup->bus_number == PCI_MCFG_BUS_ANY)) {
+			pr_info(PREFIX "Fixup applied: Platform [%s] domain [%d] bus number [%d]\n",
+				fixup->system->ident, fixup->domain,
+				fixup->bus_number);
+			return fixup->ops;
+		}
+		++fixup;
+	}
+
+	return NULL;
+}
+
 void __iomem *
 pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset)
 {
@@ -56,10 +82,15 @@ static struct pci_ops default_pci_mcfg_ops = {
 
 struct pci_ops *pci_mcfg_get_ops(int domain, int bus)
 {
+	struct pci_ops *pci_mcfg_ops_quirk;
+
 	/*
-	 * TODO: Match against platform specific quirks and return
-	 * corresponding PCI config space accessor set.
+	 * Match against platform specific quirks and return corresponding
+	 * PCI config space accessor set.
 	 */
+	pci_mcfg_ops_quirk = pci_mcfg_check_quirks(domain, bus);
+	if (pci_mcfg_ops_quirk)
+		return pci_mcfg_ops_quirk;
 
 	return &default_pci_mcfg_ops;
 }
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index c4bd0e2..c93fc97 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -298,6 +298,13 @@
 		VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .;	\
 	}								\
 									\
+	/* ACPI MCFG quirks */						\
+	.acpi_fixup        : AT(ADDR(.acpi_fixup) - LOAD_OFFSET) {	\
+		VMLINUX_SYMBOL(__start_acpi_mcfg_fixups) = .;		\
+		*(.acpi_fixup_mcfg)					\
+		VMLINUX_SYMBOL(__end_acpi_mcfg_fixups) = .;		\
+	}								\
+									\
 	/* Built-in firmware blobs */					\
 	.builtin_fw        : AT(ADDR(.builtin_fw) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start_builtin_fw) = .;			\
diff --git a/include/linux/ecam.h b/include/linux/ecam.h
index e0f322e..1319fa8 100644
--- a/include/linux/ecam.h
+++ b/include/linux/ecam.h
@@ -20,6 +20,23 @@ struct pci_mmcfg_region {
 	bool hot_added;
 };
 
+struct pci_mcfg_fixup {
+	const struct dmi_system_id *system;
+	struct pci_ops *ops;
+	int domain;
+	int bus_number;
+};
+
+#define PCI_MCFG_DOMAIN_ANY	-1
+#define PCI_MCFG_BUS_ANY	-1
+
+/* Designate a routine to fix up buggy MCFG */
+#define DECLARE_ACPI_MCFG_FIXUP(system, ops, dom, bus)			\
+	static const struct pci_mcfg_fixup __mcfg_fixup_##system##dom##bus\
+	 __used	__attribute__((__section__(".acpi_fixup_mcfg"),		\
+				aligned((sizeof(void *))))) =		\
+	{ system, ops, dom, bus };
+
 struct pci_mmcfg_region *pci_mmconfig_lookup(int segment, int bus);
 struct pci_mmcfg_region *pci_mmconfig_alloc(int segment, int start,
 						   int end, u64 addr);
-- 
1.9.1