linux-kernel - Re: [PATCH v5 1/2] of: Documentation: Specify local APIC ID in "reg"

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Message-ID: <1520963414.38672.31.camel@intel.com>
Date:   Tue, 13 Mar 2018 10:50:14 -0700
From:   Ivan Gorinov <ivan.gorinov@...el.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Frank Rowand <frowand.list@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v5 1/2] of: Documentation: Specify local APIC ID in "reg"

On Tue, 2018-03-13 at 11:01 +0000, Mark Rutland wrote:

> > +		cpu@1 {
> > +			device_type = "cpu";
> > +			compatible = "intel,ce4100";
> > +			reg = <0x02>;
> > +		};
> The unit-address (the bit after the '@' in the node name) should match
> the reg, so this node should be named cpu@2.

OK

> > -The reg property describes the CPU number. The lapic property points to
> > -the local APIC timer.
> Why was the lapic phandle removed?

The "lapic" node may not be required.

Local APIC is an essential part of every logical CPU described by a "cpu"
node, with registers accessed as memory-mapped I/O (except for x2APIC mode).
Current implementation of local APIC kernel driver requires base address to
be the same on all CPUs, default 0xfee00000. If the base address is changed
by firmware, one optional node can describe new address for all CPUs.