---
 drivers/cpufreq/intel_pstate.c |   53 ++++++++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 11 deletions(-)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -897,11 +897,19 @@ static ssize_t show_base_frequency(struc
 
 cpufreq_freq_attr_ro(base_frequency);
 
+enum hwp_cpufreq_attr_index {
+	HWP_BASE_FREQUENCY_INDEX = 0,
+	HWP_PERFORMANCE_PREFERENCE_INDEX,
+	HWP_PERFORMANCE_AVAILABLE_PREFERENCES_INDEX,
+	HWP_CPUFREQ_ATTR_COUNT,
+};
+
 static struct freq_attr *hwp_cpufreq_attrs[] = {
-	&energy_performance_preference,
-	&energy_performance_available_preferences,
-	&base_frequency,
-	NULL,
+	[HWP_BASE_FREQUENCY_INDEX] = &base_frequency,
+	[HWP_PERFORMANCE_PREFERENCE_INDEX] = &energy_performance_preference,
+	[HWP_PERFORMANCE_AVAILABLE_PREFERENCES_INDEX] =
+				&energy_performance_available_preferences,
+	[HWP_CPUFREQ_ATTR_COUNT] = NULL,
 };
 
 static bool no_cas __ro_after_init;
@@ -1370,6 +1378,9 @@ static void intel_pstate_hwp_offline(str
 #define POWER_CTL_EE_ENABLE	1
 #define POWER_CTL_EE_DISABLE	2
 
+/* Enable bit for Dynamic Efficiency Control (DEC) */
+#define POWER_CTL_DEC_ENABLE	27
+
 static int power_ctl_ee_state;
 
 static void set_power_ctl_ee_state(bool input)
@@ -3759,6 +3770,30 @@ static const struct x86_cpu_id intel_hyb
 	{}
 };
 
+static bool hwp_is_supported(void)
+{
+	u64 power_ctl;
+
+	/*
+	 * Avoid enabling HWP for processors without EPP support unless the
+	 * Dynamic Efficiency Control (DEC) enable bit (MSR_IA32_POWER_CTL,
+	 * bit 27) is set because that means incomplete HWP implementation
+	 * which is a corner case and supporting it is generally problematic.
+	 */
+	if (boot_cpu_has(X86_FEATURE_HWP_EPP))
+		return true;
+
+	rdmsrq(MSR_IA32_POWER_CTL, power_ctl);
+	if (!(power_ctl & BIT(POWER_CTL_DEC_ENABLE)))
+		return false;
+
+	/* Without EPP support, don't expose EPP-related sysfs attributes. */
+	hwp_cpufreq_attrs[HWP_PERFORMANCE_PREFERENCE_INDEX] = NULL;
+	hwp_cpufreq_attrs[HWP_PERFORMANCE_AVAILABLE_PREFERENCES_INDEX] = NULL;
+
+	return true;
+}
+
 static int __init intel_pstate_init(void)
 {
 	static struct cpudata **_all_cpu_data;
@@ -3788,14 +3823,10 @@ static int __init intel_pstate_init(void
 
 		copy_cpu_funcs(&core_funcs);
 		/*
-		 * Avoid enabling HWP for processors without EPP support,
-		 * because that means incomplete HWP implementation which is a
-		 * corner case and supporting it is generally problematic.
-		 *
-		 * If HWP is enabled already, though, there is no choice but to
-		 * deal with it.
+		 * If HWP is enabled already, there is no choice but to deal
+		 * with it.
 		 */
-		if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) || hwp_forced) {
+		if (hwp_forced || (!no_hwp && hwp_is_supported())) {
 			hwp_active = true;
 			hwp_mode_bdw = id->driver_data;
 			intel_pstate.attr = hwp_cpufreq_attrs;