netdev - Re: [net-next PATCH v7 1/6] Documentation: ACPI: DSD: Document MDIO PHY

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Date:   Tue, 29 Sep 2020 17:46:53 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Calvin Johnson <calvin.johnson@....nxp.com>,
        Grant Likely <grant.likely@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Jon <jon@...id-run.com>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        netdev <netdev@...r.kernel.org>, "linux.cj" <linux.cj@...il.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        nd <nd@....com>
Subject: Re: [net-next PATCH v7 1/6] Documentation: ACPI: DSD: Document MDIO PHY

On Tue, Sep 29, 2020 at 5:32 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Tue, Sep 29, 2020 at 04:55:40PM +0300, Andy Shevchenko wrote:
> > On Tue, Sep 29, 2020 at 4:43 PM Andrew Lunn <andrew@...n.ch> wrote:
> > > On Tue, Sep 29, 2020 at 10:47:03AM +0530, Calvin Johnson wrote:
> > > > On Fri, Sep 25, 2020 at 02:34:21PM +0100, Grant Likely wrote:
> >
> > ...
> >
> > > Newbie ACPI question: Does ACPI even support big endian CPUs, given
> > > its x86 origins?
> >
> > I understand the newbie part, but can you elaborate what did you mean
> > under 'support'?
> > To me it sounds like 'network stack was developed for BE CPUs, does it
> > support LE ones?'
>
> Does ACPI define the endianness of its tables? Is it written in the
> standard that they should be little endian?

5.2:
"All numeric values in ACPI-defined tables, blocks, and structures are
always encoded in little endian
format. Signature values are stored as fixed-length strings."

>  Does Tianocore, or any
> other implementations, have the needed le32_to_cpu() calls so that
> they can boot on a big endian CPU?

Not of my knowledge.

> Does it have a standardized way of
> saying a device is big endian, swap words around if appropriate when
> doing IO?

I guess this is not applicable to ACPI. Does Linux have a standardized way?
So, what did you mean under doing I/O? I mean in which context?

> Is it feasible to boot an ARM system big endian?

Not an ARM guy.

> Can i boot the same
> system little endian? The CPU should be able to do it, but are the
> needed things in the ACPI specification and implementation to allow
> it?

-- 
With Best Regards,
Andy Shevchenko