linux-kernel - [PATCH v4 2/4] dt-bindings: x86: apic: Introduce new optional bool property for lapic

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Date:   Wed, 23 Nov 2022 17:38:18 +0800
From:   Rahul Tanwar <rtanwar@...linear.com>
To:     Rahul Tanwar <rtanwar@...linear.com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, <linux-lgm-soc@...linear.com>
Subject: [PATCH v4 2/4] dt-bindings: x86: apic: Introduce new optional bool property for lapic

Intel defines a few possible interrupt delivery modes. With respect
to boot/init time, mainly two interrupt delivery modes are possible.
PIC Mode - Legacy external 8259 compliant PIC interrupt controller.
Virtual Wire Mode - use lapic as virtual wire interrupt delivery mode.

For ACPI or MPS spec compliant systems, it is figured out by some read
only bit field/s available in their respective defined data structures.
But for OF based systems, it is by default set to PIC mode. Presently,
it is hardcoded to legacy PIC mode for OF based x86 systems with no
option to choose the configuration between PIC mode & virtual wire mode.

For this purpose, introduce a new boolean property for interrupt
controller node of lapic which can allow it to be configured to virtual
wire mode as well.

Property name: 'intel,virtual-wire-mode'
Type: Boolean

If not present/not defined, interrupt delivery mode defaults to legacy PIC
mode. If present/defined, interrupt delivery mode is set to virtual wire
mode.

Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Rahul Tanwar <rtanwar@...linear.com>
---
 .../interrupt-controller/intel,ce4100-lapic.yaml   | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/devicetree/bindings/interrupt-controller/intel,ce4100-lapic.yaml b/Documentation/devicetree/bindings/interrupt-controller/intel,ce4100-lapic.yaml
index 88f320ef4616..ef47cb657335 100644
--- a/Documentation/devicetree/bindings/interrupt-controller/intel,ce4100-lapic.yaml
+++ b/Documentation/devicetree/bindings/interrupt-controller/intel,ce4100-lapic.yaml
@@ -35,6 +35,19 @@ properties:
   reg:
     maxItems: 1
 
+  intel,virtual-wire-mode:
+    description: Intel defines a few possible interrupt delivery
+      modes. With respect to boot/init time, mainly two interrupt
+      delivery modes are possible.
+      PIC Mode - Legacy external 8259 compliant PIC interrupt controller.
+      Virtual Wire Mode - use lapic as virtual wire interrupt delivery mode.
+      For ACPI or MPS spec compliant systems, it is figured out by some read
+      only bit field/s available in their respective defined data structures.
+      For OF based systems, it is by default set to PIC mode.
+      But if this optional boolean property is set, then the interrupt delivery
+      mode is configured to virtual wire compatibility mode.
+    type: boolean
+
 required:
   - compatible
   - reg
@@ -46,4 +59,5 @@ examples:
     lapic0: interrupt-controller@...00000 {
         compatible = "intel,ce4100-lapic";
         reg = <0xfee00000 0x1000>;
+        intel,virtual-wire-mode;
     };
-- 
2.17.1