PCI/ACPI: negotiate CXL _OSC

Add full support for negotiating _OSC as defined in the CXL 2.0 spec, as
applicable to CXL-enabled platforms. Advertise support for the CXL
features we support - 'CXL 2.0 port/device register access', 'Protocol
Error Reporting', and 'CXL Native Hot Plug'. Request control for 'CXL
Memory Error Reporting'. The requests are dependent on CONFIG_* based
prerequisites, and prior PCI enabling, similar to how the standard PCI
_OSC bits are determined.

The CXL specification does not define any additional constraints on
the hotplug flow beyond PCIe native hotplug, so a kernel that supports
native PCIe hotplug, supports CXL hotplug. For error handling protocol
and link errors just use PCIe AER. There is nascent support for
amending AER events with CXL specific status [1], but there's
otherwise no additional OS responsibility for CXL errors beyond PCIe
AER. CXL Memory Errors behave the same as typical memory errors so
CONFIG_MEMORY_FAILURE is sufficient to indicate support to platform
firmware.

[1]: https://lore.kernel.org/linux-cxl/164740402242.3912056.8303625392871313860.stgit@dwillia2-desk3.amr.corp.intel.com/

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20220413073618.291335-4-vishal.l.verma@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

include/acpi/acpi_bus.h

@@ -594,8 +594,10 @@ struct acpi_pci_root {
 	int bridge_type;
 	struct resource secondary;	/* downstream bus range */
 
-	u32 osc_support_set;	/* _OSC state of support bits */
-	u32 osc_control_set;	/* _OSC state of control bits */
+	u32 osc_support_set;		/* _OSC state of support bits */
+	u32 osc_control_set;		/* _OSC state of control bits */
+	u32 osc_ext_support_set;	/* _OSC state of extended support bits */
+	u32 osc_ext_control_set;	/* _OSC state of extended control bits */
 	phys_addr_t mcfg_addr;
 };
 

include/linux/acpi.h

@@ -554,10 +554,12 @@ acpi_status acpi_run_osc(acpi_handle handle, struct acpi_osc_context *context);
 #define OSC_PCI_CAPABILITY_DWORDS		3
 #define OSC_CXL_CAPABILITY_DWORDS		5
 
-/* Indexes into _OSC Capabilities Buffer (DWORDs 2 & 3 are device-specific) */
+/* Indexes into _OSC Capabilities Buffer (DWORDs 2 to 5 are device-specific) */
 #define OSC_QUERY_DWORD				0	/* DWORD 1 */
 #define OSC_SUPPORT_DWORD			1	/* DWORD 2 */
 #define OSC_CONTROL_DWORD			2	/* DWORD 3 */
+#define OSC_EXT_SUPPORT_DWORD			3	/* DWORD 4 */
+#define OSC_EXT_CONTROL_DWORD			4	/* DWORD 5 */
 
 /* _OSC Capabilities DWORD 1: Query/Control and Error Returns (generic) */
 #define OSC_QUERY_ENABLE			0x00000001  /* input */
@@ -612,6 +614,15 @@ extern u32 osc_sb_native_usb4_control;
 #define OSC_PCI_EXPRESS_LTR_CONTROL		0x00000020
 #define OSC_PCI_EXPRESS_DPC_CONTROL		0x00000080
 
+/* CXL _OSC: Capabilities DWORD 4: Support Field */
+#define OSC_CXL_1_1_PORT_REG_ACCESS_SUPPORT	0x00000001
+#define OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT	0x00000002
+#define OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT	0x00000004
+#define OSC_CXL_NATIVE_HP_SUPPORT		0x00000008
+
+/* CXL _OSC: Capabilities DWORD 5: Control Field */
+#define OSC_CXL_ERROR_REPORTING_CONTROL		0x00000001
+
 static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 {
 	u32 *ret = context->ret.pointer;
@@ -619,6 +630,13 @@ static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 	return ret[OSC_CONTROL_DWORD];
 }
 
+static inline u32 acpi_osc_ctx_get_cxl_control(struct acpi_osc_context *context)
+{
+	u32 *ret = context->ret.pointer;
+
+	return ret[OSC_EXT_CONTROL_DWORD];
+}
+
 #define ACPI_GSB_ACCESS_ATTRIB_QUICK		0x00000002
 #define ACPI_GSB_ACCESS_ATTRIB_SEND_RCV         0x00000004
 #define ACPI_GSB_ACCESS_ATTRIB_BYTE		0x00000006
@@ -1021,6 +1039,11 @@ static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 	return 0;
 }
 
+static inline u32 acpi_osc_ctx_get_cxl_control(struct acpi_osc_context *context)
+{
+	return 0;
+}
+
 #endif	/* !CONFIG_ACPI */
 
 #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC