linux-kernel - [PATCH v3] cpufreq: ondemand: Update the efficient idle check for Intel extended Families

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Message-ID: <20250826183644.220093-1-sohil.mehta@intel.com>
Date: Tue, 26 Aug 2025 11:36:44 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	linux-pm@...r.kernel.org
Cc: x86@...nel.org,
	Tony Luck <tony.luck@...el.com>,
	Zhao Liu <zhao1.liu@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Sohil Mehta <sohil.mehta@...el.com>
Subject: [PATCH v3] cpufreq: ondemand: Update the efficient idle check for Intel extended Families

IO time is considered busy by default for modern Intel processors. The
current check covers recent Family 6 models but excludes the brand new
Families 18 and 19.

According to Arjan van de Ven, the model check was mainly due to a lack
of testing on systems before INTEL_CORE2_MEROM. He suggests considering
all Intel processors as having an efficient idle.

Extend the IO busy classification to all Intel processors starting with
Family 6, including Family 15 (Pentium 4s) and upcoming Families 18/19.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
v3:
 - Posting this patch separately since the core family cleanup series
   was merged without it.
 - Improve commit message and code comments.

v2: https://lore.kernel.org/lkml/20250211194407.2577252-7-sohil.mehta@intel.com/
---
 drivers/cpufreq/cpufreq_ondemand.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 0e65d37c9231..3decfc53fe68 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -15,6 +15,10 @@
 #include <linux/tick.h>
 #include <linux/sched/cpufreq.h>
 
+#ifdef CONFIG_X86
+#include <asm/cpu_device_id.h>
+#endif
+
 #include "cpufreq_ondemand.h"
 
 /* On-demand governor macros */
@@ -41,12 +45,9 @@ static unsigned int default_powersave_bias;
 static int should_io_be_busy(void)
 {
 #if defined(CONFIG_X86)
-	/*
-	 * For Intel, Core 2 (model 15) and later have an efficient idle.
-	 */
+	/* For Intel, Family 6 and later have an efficient idle. */
 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-			boot_cpu_data.x86 == 6 &&
-			boot_cpu_data.x86_model >= 15)
+	    boot_cpu_data.x86_vfm >= INTEL_PENTIUM_PRO)
 		return 1;
 #endif
 	return 0;
-- 
2.43.0