soc: apple: Add RTKit IPC library

Apple SoCs such as the M1 come with multiple embedded co-processors
running proprietary firmware. Communication with those is established
over a simple mailbox using the RTKit IPC protocol.

This cannot be implemented inside the mailbox subsystem since on top
of communication over channels we also need support for starting,
hibernating and resetting these co-processors. We also need to
handle shared memory allocations differently depending on the
co-processor and don't want to split that across multiple drivers.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sven Peter <sven@svenpeter.dev>

1 files changed, 155 insertions, 0 deletions

diff --git a/include/linux/soc/apple/rtkit.h b/include/linux/soc/apple/rtkit.h
new file mode 100644
index 000000000000..88eb832eac7b
--- /dev/null
+++ b/include/linux/soc/apple/rtkit.h
@@ -0,0 +1,155 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/*
+ * Apple RTKit IPC Library
+ * Copyright (C) The Asahi Linux Contributors
+ *
+ * Apple's SoCs come with various co-processors running their RTKit operating
+ * system. This protocol library is used by client drivers to use the
+ * features provided by them.
+ */
+#ifndef _LINUX_APPLE_RTKIT_H_
+#define _LINUX_APPLE_RTKIT_H_
+
+#include <linux/device.h>
+#include <linux/types.h>
+#include <linux/mailbox_client.h>
+
+/*
+ * Struct to represent implementation-specific RTKit operations.
+ *
+ * @buffer:    Shared memory buffer allocated inside normal RAM.
+ * @iomem:     Shared memory buffer controlled by the co-processors.
+ * @size:      Size of the shared memory buffer.
+ * @iova:      Device VA of shared memory buffer.
+ * @is_mapped: Shared memory buffer is managed by the co-processor.
+ */
+
+struct apple_rtkit_shmem {
+	void *buffer;
+	void __iomem *iomem;
+	size_t size;
+	dma_addr_t iova;
+	bool is_mapped;
+};
+
+/*
+ * Struct to represent implementation-specific RTKit operations.
+ *
+ * @crashed:       Called when the co-processor has crashed. Runs in process
+ *                 context.
+ * @recv_message:  Function called when a message from RTKit is received
+ *                 on a non-system endpoint. Called from a worker thread.
+ * @recv_message_early:
+ *                 Like recv_message, but called from atomic context. It
+ *                 should return true if it handled the message. If it
+ *                 returns false, the message will be passed on to the
+ *                 worker thread.
+ * @shmem_setup:   Setup shared memory buffer. If bfr.is_iomem is true the
+ *                 buffer is managed by the co-processor and needs to be mapped.
+ *                 Otherwise the buffer is managed by Linux and needs to be
+ *                 allocated. If not specified dma_alloc_coherent is used.
+ *                 Called in process context.
+ * @shmem_destroy: Undo the shared memory buffer setup in shmem_setup. If not
+ *                 specified dma_free_coherent is used. Called in process
+ *                 context.
+ */
+struct apple_rtkit_ops {
+	void (*crashed)(void *cookie);
+	void (*recv_message)(void *cookie, u8 endpoint, u64 message);
+	bool (*recv_message_early)(void *cookie, u8 endpoint, u64 message);
+	int (*shmem_setup)(void *cookie, struct apple_rtkit_shmem *bfr);
+	void (*shmem_destroy)(void *cookie, struct apple_rtkit_shmem *bfr);
+};
+
+struct apple_rtkit;
+
+/*
+ * Initializes the internal state required to handle RTKit. This
+ * should usually be called within _probe.
+ *
+ * @dev:         Pointer to the device node this coprocessor is assocated with
+ * @cookie:      opaque cookie passed to all functions defined in rtkit_ops
+ * @mbox_name:   mailbox name used to communicate with the co-processor
+ * @mbox_idx:    mailbox index to be used if mbox_name is NULL
+ * @ops:         pointer to rtkit_ops to be used for this co-processor
+ */
+struct apple_rtkit *devm_apple_rtkit_init(struct device *dev, void *cookie,
+					  const char *mbox_name, int mbox_idx,
+					  const struct apple_rtkit_ops *ops);
+
+/*
+ * Reinitialize internal structures. Must only be called with the co-processor
+ * is held in reset.
+ */
+int apple_rtkit_reinit(struct apple_rtkit *rtk);
+
+/*
+ * Handle RTKit's boot process. Should be called after the CPU of the
+ * co-processor has been started.
+ */
+int apple_rtkit_boot(struct apple_rtkit *rtk);
+
+/*
+ * Quiesce the co-processor.
+ */
+int apple_rtkit_quiesce(struct apple_rtkit *rtk);
+
+/*
+ * Wake the co-processor up from hibernation mode.
+ */
+int apple_rtkit_wake(struct apple_rtkit *rtk);
+
+/*
+ * Shutdown the co-processor
+ */
+int apple_rtkit_shutdown(struct apple_rtkit *rtk);
+
+/*
+ * Checks if RTKit is running and ready to handle messages.
+ */
+bool apple_rtkit_is_running(struct apple_rtkit *rtk);
+
+/*
+ * Checks if RTKit has crashed.
+ */
+bool apple_rtkit_is_crashed(struct apple_rtkit *rtk);
+
+/*
+ * Starts an endpoint. Must be called after boot but before any messages can be
+ * sent or received from that endpoint.
+ */
+int apple_rtkit_start_ep(struct apple_rtkit *rtk, u8 endpoint);
+
+/*
+ * Send a message to the given endpoint.
+ *
+ * @rtk:            RTKit reference
+ * @ep:             target endpoint
+ * @message:        message to be sent
+ * @completeion:    will be completed once the message has been submitted
+ *                  to the hardware FIFO. Can be NULL.
+ * @atomic:         if set to true this function can be called from atomic
+ *                  context.
+ */
+int apple_rtkit_send_message(struct apple_rtkit *rtk, u8 ep, u64 message,
+			     struct completion *completion, bool atomic);
+
+/*
+ * Send a message to the given endpoint and wait until it has been submitted
+ * to the hardware FIFO.
+ * Will return zero on success and a negative error code on failure
+ * (e.g. -ETIME when the message couldn't be written within the given
+ * timeout)
+ *
+ * @rtk:            RTKit reference
+ * @ep:             target endpoint
+ * @message:        message to be sent
+ * @timeout:        timeout in milliseconds to allow the message transmission
+ *                  to be completed
+ * @atomic:         if set to true this function can be called from atomic
+ *                  context.
+ */
+int apple_rtkit_send_message_wait(struct apple_rtkit *rtk, u8 ep, u64 message,
+				  unsigned long timeout, bool atomic);
+
+#endif /* _LINUX_APPLE_RTKIT_H_ */