[tip: x86/apic] x86/of: Add support for boot time interrupt delivery mode configuration

["tip-bot2 for Rahul Tanwar" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     2833275568755eb937a52c358bf8bfa7125a463e
Gitweb:        https://git.kernel.org/tip/2833275568755eb937a52c358bf8bfa7125a463e
Author:        Rahul Tanwar <rtanwar@maxlinear.com>
AuthorDate:    Thu, 24 Nov 2022 16:41:43 +08:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Fri, 02 Dec 2022 14:57:14 +01:00

x86/of: Add support for boot time interrupt delivery mode configuration

Presently, init/boot time interrupt delivery mode is enumerated only for
ACPI enabled systems by parsing MADT table or for older systems by parsing
MP table. But for OF based x86 systems, it is assumed & hardcoded to be
legacy PIC mode. This causes a boot time crash for platforms which do not
provide a 8259 compliant legacy PIC.

Add support for configuration of init time interrupt delivery mode for x86
OF based systems by introducing a new optional boolean property
'intel,virtual-wire-mode' for the local APIC interrupt-controller
node. This property emulates IMCRP Bit 7 of MP feature info byte 2 of MP
floating pointer structure.

Defaults to legacy PIC mode if absent. Configures it to virtual wire
compatibility mode if present.

Signed-off-by: Rahul Tanwar <rtanwar@maxlinear.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221124084143.21841-5-rtanwar@maxlinear.com

---
 arch/x86/kernel/devicetree.c |  9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index 484783f..28da5dd 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -162,7 +162,14 @@ static void __init dtb_lapic_setup(void)
 			return;
 	}
 	smp_found_config = 1;
-	pic_mode = 1;
+	if (of_property_read_bool(dn, "intel,virtual-wire-mode")) {
+		pr_info("Virtual Wire compatibility mode.\n");
+		pic_mode = 0;
+	} else {
+		pr_info("IMCR and PIC compatibility mode.\n");
+		pic_mode = 1;
+	}
+
 	register_lapic_address(lapic_addr);
 }