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

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Date:   Fri, 28 May 2021 16:14:17 +0800
From:   Pu Wen <puwen@...on.cn>
To:     <linux-kernel@...r.kernel.org>
CC:     <rjw@...ysocki.net>, <rafael@...nel.org>, <len.brown@...el.com>,
        <pavel@....cz>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <bp@...e.de>, <hpa@...or.com>, <puwen@...on.cn>, <x86@...nel.org>,
        <linux-pm@...r.kernel.org>
Subject: [PATCH] x86/cstate: Allow ACPI C1 FFH MWAIT use on Hygon systems

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

The BIOS declares a C1 state in _CST to use FFH and CPUID_Fn00000005_EDX
is non-zero on Hygon systems.

Allow ffh_cstate_init() to succeed on Hygon systems to default using FFH
MWAIT instead of HALT for ACPI C1.

Tested successfully on Hygon Fam18h systems.

Signed-off-by: Pu Wen <puwen@...on.cn>
---
 arch/x86/kernel/acpi/cstate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index 49ae4e1ac9cd..7de599eba7f0 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -197,7 +197,8 @@ static int __init ffh_cstate_init(void)
 	struct cpuinfo_x86 *c = &boot_cpu_data;
 
 	if (c->x86_vendor != X86_VENDOR_INTEL &&
-	    c->x86_vendor != X86_VENDOR_AMD)
+	    c->x86_vendor != X86_VENDOR_AMD &&
+	    c->x86_vendor != X86_VENDOR_HYGON)
 		return -1;
 
 	cpu_cstate_entry = alloc_percpu(struct cstate_entry);
-- 
2.23.0