linux-kernel - Re: [PATCH 1/1] soc: keembay: Add Keem Bay IMR driver

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Date:   Mon, 25 May 2020 10:18:57 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Pavel Machek <pavel@....cz>
Cc:     Daniele Alessandrelli <daniele.alessandrelli@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Paul J Murphy <paul.j.murphy@...el.com>
Subject: Re: [PATCH 1/1] soc: keembay: Add Keem Bay IMR driver

On Sun, May 24, 2020 at 11:28 PM Pavel Machek <pavel@....cz> wrote:
>
> Hi!
>
> > > Like I said above, you just broke multi-system kernels by always
> > > trying
> > > to do this.  Trigger off of a hardware device that only your platform
> > > has in order to properly load and run.  As-is, you don't want to do
> > > this.
> >
> > My bad, I didn't consider the issue of multi-platform ARM kernels.
> >
> > The problem is that I need this code to be run early at boot, so I
> > don't think I can make this a module.
>
> How early is early enough?
>
> What bootloader are you using?
>
> I believe you should simply fix your bootloader not to pass locked memory to the kernel.
>
> Alternatively, take that memory off the "memory available" maps, and only re-add it once
> it is usable.
>
> Anything else is dangerous.

Agreed, this sounds like an incompatible extension of the boot protocol
that we should otherwise not merge.

However, there is also a lot of missing information here, and it is always
possible they are trying to something for a good reason. As long as the
problem that the bootloader is trying to solve is explained well enough
in the changelog, we can discuss it to see how it should be done properly.

       Arnd