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

From: Patryk Wlazlyn
Date: Mon Nov 25 2024 - 08:22:43 EST


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@xxxxxxxxxxxxxxx>
---
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