soc: apple: rtkit: Get rid of apple_rtkit_send_message_wait

It is fundamentally broken and has no users. Just remove it.

Acked-by: Eric Curtin <ecurtin@redhat.com>
Acked-by: Neal Gompa <neal@gompa.dev>
Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Hector Martin <marcan@marcan.st>

soc: apple: rtkit: Export non-devm init/free functions

While we normally encourage devm usage by drivers, some consumers (and
in particular the upcoming Rust abstractions) might want to manually
manage memory. Export the raw functions to make this possible.

Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Signed-off-by: Hector Martin <marcan@marcan.st>

soc: apple: rtkit: Add a private pointer to apple_rtkit_shmem

This allows downstream consumers to keep track of private data for shmem
mappings. In particular, the Rust abstraction will use this to safely
drop data associated with a mapping when it is unmapped.

Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Signed-off-by: Hector Martin <marcan@marcan.st>

soc: apple: rtkit: Add apple_rtkit_idle() function

This is yet another low power mode, used by DCP.

Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Hector Martin <marcan@marcan.st>

soc: apple: rtkit: Add apple_rtkit_poll

This allows a client to receive messages in atomic context, by polling.

Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

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>