x86/devicetree: Enable multiprocessing

Use the "reg" property to specify the processor's local APIC ID instead of setting it to the CPU node index in Device Tree.

Local APIC ID is assigned by hardware and visible in the APIC ID register. Some processor models allow APIC ID to be changed by software, but CPUID instruction executed with %eax = 0x0b always returns the initial ID in %edx.

Local APIC ID does not match the node index in many systems.

Signed-off-by Ivan Gorinov <[email protected]>

---
 Documentation/devicetree/bindings/x86/ce4100.txt | 37 ++++++++++++++++++------
 1 file changed, 28 insertions(+), 9 deletions(-)

Documentation/devicetree/bindings/x86/ce4100.txt +0 -5

index b49ae59..4bbfed1 100644
@@ -7,17 +7,36 @@ Many of the "generic" devices like HPET or IO APIC have the ce4100
 name in their compatible property because they first appeared in this
 SoC.
 
-The CPU node
-------------
-       cpu@0 {
-               device_type = "cpu";
-               compatible = "intel,ce4100";

Documentation/devicetree/bindings/x86/ce4100.txt +20 -3

+                       device_type = "cpu";
+                       compatible = "intel,ce4100";
+                       reg = <0x00>;
+               };
+
+               cpu@0x02 {
+                       device_type = "cpu";
+                       compatible = "intel,ce4100";
+                       reg = <0x02>;
+               };
        };
 
-The reg property describes the CPU number. The lapic property points to
-the local APIC timer.
+A "cpu" node describes one logical processor (hardware thread).
+
+Required properties:
+
+- device_type
+       Device type, must be "cpu".
+
+- reg
+       Local APIC ID, the unique number assigned to each processor by
+       system hardware.
 
 The SoC node
 ------------
--

2.7.4

Current x86 implementation of Device Tree does not support multiprocessing, and the bindings documentation describes the "reg" property of "cpu" nodes as "CPU number" instead of hardware-assigned local APIC ID.

v8:
* Fixed build error with CONFIG_X86_LOCAL_APIC=n reported by kbuild.

v7:
* Change log update.

v6:
* Calling of_property_read_u32() to get Local APIC ID from "reg".

* DT documentation changes: corrected CPU node example and changed the "reg" property description.

v5:
* Using the "reg" property to specify Local APIC ID.

Ivan Gorinov (2):
of: Documentation: Specify local APIC ID in "reg" x86/devicetree: Use CPU description from Device Tree

 Documentation/devicetree/bindings/x86/ce4100.txt | 37 ++++++++++++++-----
 arch/x86/kernel/devicetree.c                     | 45 +++++++++++++++++-------
 2 files changed, 61 insertions(+), 21 deletions(-)

--
2.7.4