linux-kernel - [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems

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Date:   Wed, 17 May 2017 09:20:19 -0500
From:   Yazen Ghannam <Yazen.Ghannam@....com>
To:     <linux-pm@...r.kernel.org>
CC:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <rjw@...ysocki.net>, <len.brown@...el.com>, <pavel@....cz>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems

From: Yazen Ghannam <yazen.ghannam@....com>

AMD systems support the Monitor/Mwait instructions and these can be used
for ACPI C1 in the same way as on Intel systems, with appropriate BIOS
support.

Allow ffh_cstate_init() to succeed on AMD systems and make the Cstate
description vendor-agnostic.

Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
---
 arch/x86/kernel/acpi/cstate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index 8a908ae..4c5dd5d 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -109,7 +109,7 @@ static long acpi_processor_ffh_cstate_probe_cpu(void *_cx)
 			cx->type);
 	}
 	snprintf(cx->desc,
-			ACPI_CX_DESC_LEN, "ACPI FFH INTEL MWAIT 0x%x",
+			ACPI_CX_DESC_LEN, "ACPI FFH X86 MWAIT 0x%x",
 			cx->address);
 out:
 	return retval;
@@ -169,7 +169,8 @@ static int __init ffh_cstate_init(void)
 {
 	struct cpuinfo_x86 *c = &boot_cpu_data;
 
-	if (c->x86_vendor != X86_VENDOR_INTEL)
+	if (c->x86_vendor != X86_VENDOR_INTEL &&
+	    c->x86_vendor != X86_VENDOR_AMD)
 		return -1;
 
 	cpu_cstate_entry = alloc_percpu(struct cstate_entry);
-- 
2.7.4