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Subject[RFC][PATCH 5/6] intel_idle: Refactor intel_idle_cpuidle_driver_init()
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Move the C-state verification and checks from
intel_idle_cpuidle_driver_init() to a separate function,
intel_idle_verify_cstate(), and make the former call it after
checking the CPUIDLE_FLAG_UNUSABLE state flag.

Also combine the drv->states[] updates with the incrementation of
drv->state_count.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/idle/intel_idle.c | 49 +++++++++++++++++++++++-----------------------
1 file changed, 25 insertions(+), 24 deletions(-)

Index: linux-pm/drivers/idle/intel_idle.c
===================================================================
--- linux-pm.orig/drivers/idle/intel_idle.c
+++ linux-pm/drivers/idle/intel_idle.c
@@ -944,6 +944,22 @@ static void intel_idle_s2idle(struct cpu
mwait_idle_with_hints(eax, ecx);
}

+static bool intel_idle_verify_cstate(unsigned int mwait_hint)
+{
+ unsigned int mwait_cstate = MWAIT_HINT2CSTATE(mwait_hint) + 1;
+ unsigned int num_substates = (mwait_substates >> mwait_cstate * 4) &
+ MWAIT_SUBSTATE_MASK;
+
+ /* Ignore the C-state if there are NO sub-states in CPUID for it. */
+ if (num_substates == 0)
+ return false;
+
+ if (mwait_cstate > 2 && !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+ mark_tsc_unstable("TSC halts in idle states deeper than C2");
+
+ return true;
+}
+
static void __setup_broadcast_timer(bool on)
{
if (on)
@@ -1332,10 +1348,10 @@ static void __init intel_idle_cpuidle_dr
drv->state_count = 1;

for (cstate = 0; cstate < CPUIDLE_STATE_MAX; ++cstate) {
- int num_substates, mwait_hint, mwait_cstate;
+ unsigned int mwait_hint;

- if ((cpuidle_state_table[cstate].enter == NULL) &&
- (cpuidle_state_table[cstate].enter_s2idle == NULL))
+ if (!cpuidle_state_table[cstate].enter &&
+ !cpuidle_state_table[cstate].enter_s2idle)
break;

if (cstate + 1 > max_cstate) {
@@ -1343,34 +1359,19 @@ static void __init intel_idle_cpuidle_dr
break;
}

- mwait_hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
- mwait_cstate = MWAIT_HINT2CSTATE(mwait_hint);
-
- /* number of sub-states for this state in CPUID.MWAIT */
- num_substates = (mwait_substates >> ((mwait_cstate + 1) * 4))
- & MWAIT_SUBSTATE_MASK;
-
- /* if NO sub-states for this state in CPUID, skip it */
- if (num_substates == 0)
- continue;
-
- /* if state marked as disabled, skip it */
+ /* If marked as unusable, skip this state. */
if (cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_UNUSABLE) {
pr_debug("state %s is disabled\n",
cpuidle_state_table[cstate].name);
continue;
}

+ mwait_hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
+ if (!intel_idle_verify_cstate(mwait_hint))
+ continue;

- if (((mwait_cstate + 1) > 2) &&
- !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
- mark_tsc_unstable("TSC halts in idle"
- " states deeper than C2");
-
- drv->states[drv->state_count] = /* structure copy */
- cpuidle_state_table[cstate];
-
- drv->state_count += 1;
+ /* Structure copy. */
+ drv->states[drv->state_count++] = cpuidle_state_table[cstate];
}

if (icpu->byt_auto_demotion_disable_flag) {


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