linux-kernel - Re: [RFC PATCH 1/3] of: reserved_mem: Change the order that reserved

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Date:   Tue, 24 Oct 2023 14:15:48 -0500
From:   Rob Herring <robh@...nel.org>
To:     Oreoluwa Babatunde <quic_obabatun@...cinc.com>
Cc:     catalin.marinas@....com, will@...nel.org, frowand.list@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        kernel@...cinc.com
Subject: Re: [RFC PATCH 1/3] of: reserved_mem: Change the order that
 reserved_mem regions are stored

On Thu, Oct 19, 2023 at 03:45:37PM -0700, Oreoluwa Babatunde wrote:
> 
> On 10/19/2023 12:46 PM, Rob Herring wrote:
> > On Thu, Oct 19, 2023 at 1:49 PM Oreoluwa Babatunde
> > <quic_obabatun@...cinc.com> wrote:
> >> The dynamic allocation of the reserved_mem array needs to be done after
> >> paging_init() is called because memory allocated using memblock_alloc()
> >> is not writeable before that.


> >> --- a/arch/arm64/kernel/setup.c
> >> +++ b/arch/arm64/kernel/setup.c
> >> @@ -27,6 +27,8 @@
> >>  #include <linux/proc_fs.h>
> >>  #include <linux/memblock.h>
> >>  #include <linux/of_fdt.h>
> >> +#include <linux/of_reserved_mem.h>
> >> +
> >>  #include <linux/efi.h>
> >>  #include <linux/psci.h>
> >>  #include <linux/sched/task.h>
> >> @@ -346,6 +348,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
> >>
> >>         paging_init();
> >>
> >> +       fdt_init_reserved_mem();
> >> +
> > You removed this call from the common code and add it to arm64 arch
> > code, doesn't that break every other arch?
> Yes, the same changes will be needed for every other arch. I was hoping to
> get some feedback on the RFC before implementing this on other archs which
> is why the change is currently only in arm64.
> > The very next thing done here is unflattening the DT. So another call
> > from the arch code to the DT code isn't needed either.
> Yes, I see that unflatten_device_tree() is being called right after here.
> Just to clarify, are you suggesting to move fdt_init_reserved_mem() into the
> unflatten_device_tree() call?

In general, I want fewer calls between arch code and DT core and for the 
DT core to be more in control of the ordering that things happen. Your 
series does the opposite.

Rob