linux-kernel - Re: [PATCH v16 06/16] lib: fdt: add a helper function for handling memory range property

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Message-ID: <681e1265-2f0c-2a62-3778-09911b2be7fc@arm.com>
Date:   Fri, 7 Dec 2018 10:12:47 +0000
From:   James Morse <james.morse@....com>
To:     Will Deacon <will.deacon@....com>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        David Howells <dhowells@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        David Miller <davem@...emloft.net>, dyoung@...hat.com,
        Baoquan He <bhe@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        prudo@...ux.ibm.com, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        bhsharma@...hat.com, kexec@...ts.infradead.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v16 06/16] lib: fdt: add a helper function for handling
 memory range property

Hi Akashi, Will,

On 06/12/2018 15:54, Will Deacon wrote:
> On Thu, Dec 06, 2018 at 08:47:04AM -0600, Rob Herring wrote:
>> On Wed, Nov 14, 2018 at 11:52 PM AKASHI Takahiro
>> <takahiro.akashi@...aro.org> wrote:
>>>
>>> Added function, fdt_setprop_reg(), will be used later to handle
>>> kexec-specific property in arm64's kexec_file implementation.
>>> It will possibly be merged into libfdt in the future.
>>
>> You generally can't modify libfdt files. Any changes will be blown
>> away with the next dtc sync (there's one in -next now). Though here
>> you are creating a new location with fdt code. lib/ is just a shim to
>> the actual libfdt code. Don't put any implementation there. You can
>> add this to drivers/of/fdt_address.c for the short term, but it still
>> needs to go upstream.
>>
>> Otherwise, the implementation looks fine to me.
> 
> I agree, but I don't think there's a real need for us to hack
> drivers/of/fdt_address.c in the meantime -- let's just target upstream
> and not carry this in the kernel.
> 
> Akashi -- for now, I'll drop the kdump parts of this series which rely
> on this helper. The majority of the series is actually independent and
> can go in as-is.
> 
> I've pushed out a kexec branch to the arm64 tree for you to take a look
> at:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=kexec

I gave this a quick spin. Without the elfcorehdr/usable-memory-range arm64 needs
to explicitly forbid kdump via kexec_file_load. (like powerpc does already).
Without this kdump works, but the second kernel overwrites the first as those DT
properties are missing.

I'll post a patch momentarily,


Thanks,

James