On Wed, Jun 9, 2021 at 7:30 PM Rafael J. Wysocki [off-list ref] wrote:

On Fri, May 28, 2021 at 10:44 AM Pu Wen [off-list ref] wrote:

quoted

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@hygon.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);
--

Applied as 5.14 material, thanks!

And dropped, because it has been applied already by Boris:
https://git.kernel.org/tip/280b68a3b3b96b027fcdeb5a3916a8e2aaf84d03