From 2366c7fdb59812bbd1382afed69e250582c64187 Mon Sep 17 00:00:00 2001
From: Shannon Zhao <shannon.zhao@linaro.org>
Date: Thu, 7 Apr 2016 20:03:29 +0800
Subject: ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
a /hypervisor node in DT. So check if it needs to enable ACPI.

Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Julien Grall <julien.grall@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index d1ce8e2..57ee317 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -67,10 +67,15 @@ static int __init dt_scan_depth1_nodes(unsigned long node,
 {
 	/*
 	 * Return 1 as soon as we encounter a node at depth 1 that is
-	 * not the /chosen node.
+	 * not the /chosen node, or /hypervisor node with compatible
+	 * string "xen,xen".
 	 */
-	if (depth == 1 && (strcmp(uname, "chosen") != 0))
-		return 1;
+	if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
+		if (strcmp(uname, "hypervisor") != 0 ||
+		    !of_flat_dt_is_compatible(node, "xen,xen"))
+			return 1;
+	}
+
 	return 0;
 }
 
@@ -184,7 +189,8 @@ void __init acpi_boot_table_init(void)
 	/*
 	 * Enable ACPI instead of device tree unless
 	 * - ACPI has been disabled explicitly (acpi=off), or
-	 * - the device tree is not empty (it has more than just a /chosen node)
+	 * - the device tree is not empty (it has more than just a /chosen node,
+	 *   and a /hypervisor node when running on Xen)
 	 *   and ACPI has not been force enabled (acpi=force)
 	 */
 	if (param_acpi_off ||
-- 
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