One of the preceding commits removed the CPUID leaf 0x5 based play_dead
in favor of delegating the play_dead functionality to the idle driver.
It was mainly (perhaps exclusively) used for Intel CPUs. Add handling of
the FFH states to the acpi idle driver in case intel idle is missing.

Notice, that on Intel, play_dead code relies on intel idle driver to be
present or BIOS to expose the desired states now. On AMD, since the
preferred play_dead method is via HLT or IOPORT over FFH/MWAIT, the code
relies on BIOS to expose the states that will allow for efficient
play_dead.

Suggested-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@linux.intel.com>
---
 arch/x86/kernel/acpi/cstate.c | 9 +++++++++
 drivers/acpi/processor_idle.c | 2 ++
 include/acpi/processor.h      | 5 +++++
 3 files changed, 16 insertions(+)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index f3ffd0a3a012..ee2933001acf 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -204,6 +204,15 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
 }
 EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
 
+void acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx)
+{
+	unsigned int cpu = smp_processor_id();
+	struct cstate_entry *percpu_entry;
+
+	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
+	mwait_play_dead(percpu_entry->states[cx->index].eax);
+}
+
 void __cpuidle acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
 {
 	unsigned int cpu = smp_processor_id();
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index ce728cf7e301..83213fa47c1b 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -590,6 +590,8 @@ static void acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 			raw_safe_halt();
 		else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
 			io_idle(cx->address);
+		} else if (cx->entry_method == ACPI_CSTATE_FFH) {
+			acpi_processor_ffh_play_dead(cx);
 		} else
 			return;
 	}
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index a17e97e634a6..63a37e72b721 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -280,6 +280,7 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
 				    struct acpi_processor_cx *cx,
 				    struct acpi_power_register *reg);
 void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cstate);
+void acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx);
 #else
 static inline void acpi_processor_power_init_bm_check(struct
 						      acpi_processor_flags
@@ -300,6 +301,10 @@ static inline void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx
 {
 	return;
 }
+static inline void acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx)
+{
+	return;
+}
 #endif
 
 static inline int call_on_cpu(int cpu, long (*fn)(void *), void *arg,
-- 
2.47.1