linux-kernel - Re: [PATCH v3 1/3] of/fdt: Absorb ARM64's __early_init_dt_declare

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Message-ID: <20181025140636.GA30658@n2100.armlinux.org.uk>
Date:   Thu, 25 Oct 2018 15:06:36 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        devicetree@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        christoffer.dall@....com,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        bcm-kernel-feedback-list@...adcom.com, andreyknvl@...gle.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frank Rowand <frowand.list@...il.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/3] of/fdt: Absorb ARM64's
 __early_init_dt_declare_initrd()

On Thu, Oct 25, 2018 at 08:25:04AM -0500, Rob Herring wrote:
> On Wed, Oct 24, 2018 at 7:17 PM Florian Fainelli <f.fainelli@...il.com> wrote:
> >
> > ARM64 is the only architecture that requires a re-definition of
> > __early_init_dt_declare_initrd(), absorb its custom implemention in
> > drivers/of/fdt.c.
> >
> > Suggested-by: Rob Herring <robh@...nel.org.
> 
> You forgot a shift key. :)
> 
> > Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> > ---
> >  drivers/of/fdt.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index 800ad252cf9c..7d316f008f22 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -896,9 +896,14 @@ const void * __init of_flat_dt_match_machine(const void *default_match,
> >  static void __early_init_dt_declare_initrd(unsigned long start,
> >                                            unsigned long end)
> >  {
> > +#if IS_ENABLED(CONFIG_ARM64)
> 
> C code, not preprocessor please.
> 
> > +       initrd_start = start;
> > +       initrd_end = end;
> 
> Thinking some more about this, perhaps it is better to just add the
> *_phys variants now along side the VA variants and set them here. Then
> the arm64 code can override the initrd_start, initrd_end, and
> initrd_below_start_ok values.

Please, let's not make the age old mistake of inventing new symbols
for stuff that already exists:

$ grep phys_initrd_start arch/ -rl
arch/arm/mm/init.c
arch/nds32/mm/init.c
arch/unicore32/mm/init.c
$ grep initrd_start_phys arch/ -rl
$

Please use the "phys_initrd_start" and "phys_initrd_end" naming,
which already exist on some architectures rather than inventing a new
set of symbols for the same thing and then forcing arches to change.
We could then get rid of:

        /* FDT scan will populate initrd_start */
        if (initrd_start && !phys_initrd_size) {
                phys_initrd_start = __virt_to_phys(initrd_start);
                phys_initrd_size = initrd_end - initrd_start;
        }

        initrd_start = initrd_end = 0;

in ARM, which exists purely to cope with DT.

-- 
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