linux-kernel - [PATCH] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS

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Date:   Wed,  8 Sep 2021 20:48:02 -0700
From:   Doug Smythies <doug.smythies@...il.com>
To:     srinivas.pandruvada@...ux.intel.com, rafael@...nel.org,
        len.brown@...el.com
Cc:     dsmythies@...us.net, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: [PATCH] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS

If HWP has been already been enabled by BIOS, it may be
necessary to override some kernel command line parameters.
Once it has been enabled it requires a reset to be disabled.

Signed-off-by: Doug Smythies <dsmythies@...us.net>
---
 drivers/cpufreq/intel_pstate.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index bb4549959b11..073bae5d4498 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3267,7 +3267,7 @@ static int __init intel_pstate_init(void)
 		 */
 		if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) ||
 		    intel_pstate_hwp_is_enabled()) {
-			hwp_active++;
+			hwp_active = 1;
 			hwp_mode_bdw = id->driver_data;
 			intel_pstate.attr = hwp_cpufreq_attrs;
 			intel_cpufreq.attr = hwp_cpufreq_attrs;
@@ -3347,17 +3347,27 @@ device_initcall(intel_pstate_init);
 
 static int __init intel_pstate_setup(char *str)
 {
+	/*
+	 * If BIOS is forcing HWP, then parameter
+	 * overrides might be needed. Only print
+	 * the message once, and regardless of
+	 * any overrides.
+	 */
+	if(!hwp_active && boot_cpu_has(X86_FEATURE_HWP))
+		if(intel_pstate_hwp_is_enabled()){
+			pr_info("HWP enabled by BIOS\n");
+			hwp_active = 1;
+		}
 	if (!str)
 		return -EINVAL;
 
-	if (!strcmp(str, "disable"))
+	if (!strcmp(str, "disable") && !hwp_active)
 		no_load = 1;
-	else if (!strcmp(str, "active"))
+	if (!strcmp(str, "active"))
 		default_driver = &intel_pstate;
-	else if (!strcmp(str, "passive"))
+	if (!strcmp(str, "passive"))
 		default_driver = &intel_cpufreq;
-
-	if (!strcmp(str, "no_hwp")) {
+	if (!strcmp(str, "no_hwp") && !hwp_active) {
 		pr_info("HWP disabled\n");
 		no_hwp = 1;
 	}
-- 
2.25.1