firmware: arm_sdei: Add driver for Software Delegated Exceptions

The Software Delegated Exception Interface (SDEI) is an ARM standard
for registering callbacks from the platform firmware into the OS.
This is typically used to implement firmware notifications (such as
firmware-first RAS) or promote an IRQ that has been promoted to a
firmware-assisted NMI.

Add the code for detecting the SDEI version and the framework for
registering and unregistering events. Subsequent patches will add the
arch-specific backend code and the necessary power management hooks.

Only shared events are supported, power management, private events and
discovery for ACPI systems will be added by later patches.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/include/linux/arm_sdei.h b/include/linux/arm_sdei.h
new file mode 100644
index 000000000000..942afbd544b7
--- /dev/null
+++ b/include/linux/arm_sdei.h
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2017 Arm Ltd.
+#ifndef __LINUX_ARM_SDEI_H
+#define __LINUX_ARM_SDEI_H
+
+#include <uapi/linux/arm_sdei.h>
+
+enum sdei_conduit_types {
+	CONDUIT_INVALID = 0,
+	CONDUIT_SMC,
+	CONDUIT_HVC,
+};
+
+#include <asm/sdei.h>
+
+/* Arch code should override this to set the entry point from firmware... */
+#ifndef sdei_arch_get_entry_point
+#define sdei_arch_get_entry_point(conduit)	(0)
+#endif
+
+/*
+ * When an event occurs sdei_event_handler() will call a user-provided callback
+ * like this in NMI context on the CPU that received the event.
+ */
+typedef int (sdei_event_callback)(u32 event, struct pt_regs *regs, void *arg);
+
+/*
+ * Register your callback to claim an event. The event must be described
+ * by firmware.
+ */
+int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg);
+
+/*
+ * Calls to sdei_event_unregister() may return EINPROGRESS. Keep calling
+ * it until it succeeds.
+ */
+int sdei_event_unregister(u32 event_num);
+
+int sdei_event_enable(u32 event_num);
+int sdei_event_disable(u32 event_num);
+
+#ifdef CONFIG_ARM_SDE_INTERFACE
+/* For use by arch code when CPU hotplug notifiers are not appropriate. */
+int sdei_mask_local_cpu(void);
+int sdei_unmask_local_cpu(void);
+#else
+static inline int sdei_mask_local_cpu(void) { return 0; }
+static inline int sdei_unmask_local_cpu(void) { return 0; }
+#endif /* CONFIG_ARM_SDE_INTERFACE */
+
+
+/*
+ * This struct represents an event that has been registered. The driver
+ * maintains a list of all events, and which ones are registered. (Private
+ * events have one entry in the list, but are registered on each CPU).
+ * A pointer to this struct is passed to firmware, and back to the event
+ * handler. The event handler can then use this to invoke the registered
+ * callback, without having to walk the list.
+ *
+ * For CPU private events, this structure is per-cpu.
+ */
+struct sdei_registered_event {
+	/* For use by arch code: */
+	struct pt_regs          interrupted_regs;
+
+	sdei_event_callback	*callback;
+	void			*callback_arg;
+	u32			 event_num;
+	u8			 priority;
+};
+
+/* The arch code entry point should then call this when an event arrives. */
+int notrace sdei_event_handler(struct pt_regs *regs,
+			       struct sdei_registered_event *arg);
+
+/* arch code may use this to retrieve the extra registers. */
+int sdei_api_event_context(u32 query, u64 *result);
+
+#endif /* __LINUX_ARM_SDEI_H */