linux-kernel - Re: [PATCH 5/9] soc: apple: Add RTKit IPC library

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Date:   Mon, 4 Apr 2022 10:02:29 -0500
From:   Rob Herring <robh@...nel.org>
To:     Sven Peter <sven@...npeter.dev>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>,
        Hector Martin <marcan@...can.st>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Arnd Bergmann <arnd@...db.de>, Keith Busch <kbusch@...nel.org>,
        "axboe@...com" <axboe@...com>, "hch@....de" <hch@....de>,
        "sagi@...mberg.me" <sagi@...mberg.me>,
        Marc Zyngier <maz@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org
Subject: Re: [PATCH 5/9] soc: apple: Add RTKit IPC library

On Sat, Apr 02, 2022 at 03:51:46PM +0200, Sven Peter wrote:
> On Wed, Mar 23, 2022, at 12:19, Krzysztof Kozlowski wrote:
> > On 21/03/2022 17:50, Sven Peter wrote:
> >> 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.
> >> 
> >> Signed-off-by: Sven Peter <sven@...npeter.dev>
> >> ---
> >>  drivers/soc/apple/Kconfig          |  13 +
> >>  drivers/soc/apple/Makefile         |   3 +
> >>  drivers/soc/apple/rtkit-crashlog.c | 147 +++++
> >>  drivers/soc/apple/rtkit-internal.h |  76 +++
> >>  drivers/soc/apple/rtkit.c          | 842 +++++++++++++++++++++++++++++
> >>  include/linux/soc/apple/rtkit.h    | 203 +++++++
> >>  6 files changed, 1284 insertions(+)
> >
> > Isn't this some implementation of a mailbox? If so, it should be in
> > drivers/mailbox. Please don't put all stuff in soc/apple, that's not how
> > Linux is organized. To drivers/soc usually we put drivers which do not
> > fit regular subsystems.
> >
> 
> I put this into soc/apple because I don't think it fits within the mailbox
> framework very well.
> (It actually uses the mailbox framework for the actual communication
> with the hardware with a driver that's already upstream.)
> 
> Essentially, the mailbox subsystem provides a common API to send and
> receive messages over indepedent hardware channels and devicetree bindings
> to describe the relationship between those channels and other drivers.
> 
> One of the features that doesn't really fit is that we need to be able
> to start, shutdown and re-start these co-processors. The NVMe driver

remoteproc does that. Did you look at it? Most remoteproc drivers use 
some combination of mailboxes and shared memory.

Rob