[RFC PATCH v4 6/8] intel_idle: Provide enter_dead() handler for SRF

[Patryk Wlazlyn <patryk.wlazlyn@linux.intel.com>]

Intel's Sierra Forest report two C6 substates in cpuid leaf 5:
    C6S  (hint 0x22)
    C6SP (hint 0x23)

Hints 0x20 and 0x21 are skipped entirely, causing the generic
implementation in mwait_play_dead() to compute the wrong hint, when
looking for the deepest cstate. As a result, package with an offlined
CPU can never reach PC6.

Define the enter_dead() handler for SRF.

Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@linux.intel.com>
---
 drivers/idle/intel_idle.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index ac4d8faa3886..c2ca01e74add 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -56,6 +56,7 @@
 #include <asm/mwait.h>
 #include <asm/spec-ctrl.h>
 #include <asm/fpu/api.h>
+#include <asm/smp.h>
 
 #define INTEL_IDLE_VERSION "0.5.1"
 
@@ -227,6 +228,16 @@ static __cpuidle int intel_idle_s2idle(struct cpuidle_device *dev,
 	return 0;
 }
 
+static __cpuidle void intel_idle_enter_dead(struct cpuidle_device *dev,
+					    int index)
+{
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
+	struct cpuidle_state *state = &drv->states[index];
+	unsigned long eax = flg2MWAIT(state->flags);
+
+	mwait_play_dead_with_hint(eax);
+}
+
 /*
  * States are indexed by the cstate number,
  * which is also the index into the MWAIT hint array.
@@ -1391,6 +1402,7 @@ static struct cpuidle_state srf_cstates[] __initdata = {
 		.exit_latency = 1,
 		.target_residency = 1,
 		.enter = &intel_idle,
+		.enter_dead = &intel_idle_enter_dead,
 		.enter_s2idle = intel_idle_s2idle, },
 	{
 		.name = "C1E",
@@ -1399,6 +1411,7 @@ static struct cpuidle_state srf_cstates[] __initdata = {
 		.exit_latency = 2,
 		.target_residency = 10,
 		.enter = &intel_idle,
+		.enter_dead = &intel_idle_enter_dead,
 		.enter_s2idle = intel_idle_s2idle, },
 	{
 		.name = "C6S",
@@ -1408,6 +1421,7 @@ static struct cpuidle_state srf_cstates[] __initdata = {
 		.exit_latency = 270,
 		.target_residency = 700,
 		.enter = &intel_idle,
+		.enter_dead = &intel_idle_enter_dead,
 		.enter_s2idle = intel_idle_s2idle, },
 	{
 		.name = "C6SP",
@@ -1417,6 +1431,7 @@ static struct cpuidle_state srf_cstates[] __initdata = {
 		.exit_latency = 310,
 		.target_residency = 900,
 		.enter = &intel_idle,
+		.enter_dead = &intel_idle_enter_dead,
 		.enter_s2idle = intel_idle_s2idle, },
 	{
 		.enter = NULL }
-- 
2.47.0