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From:   Doug Smythies <doug.smythies@gmail.com>
To:     srinivas.pandruvada@linux.intel.com, rafael@kernel.org,
        len.brown@intel.com
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Doug Smythies <dsmythies@telus.net>
Subject: [PATCH v2] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS
Date:   Sun, 12 Sep 2021 11:50:29 -0700
Message-Id: <20210912185029.5704-1-dsmythies@telus.net>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Doug Smythies <dsmythies@telus.net>
---
 drivers/cpufreq/intel_pstate.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 1097f826ad70..8c176b7dae41 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3205,11 +3205,15 @@ static int __init intel_pstate_init(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 		return -ENODEV;
 
-	if (no_load)
-		return -ENODEV;
-
 	id = x86_match_cpu(hwp_support_ids);
 	if (id) {
+		bool hwp_forced = intel_pstate_hwp_is_enabled();
+
+		if (hwp_forced)
+			pr_info("HWP enabled by BIOS\n");
+		else if (no_load)
+			return -ENODEV;
+
 		copy_cpu_funcs(&core_funcs);
 		/*
 		 * Avoid enabling HWP for processors without EPP support,
@@ -3219,8 +3223,7 @@ static int __init intel_pstate_init(void)
 		 * If HWP is enabled already, though, there is no choice but to
 		 * deal with it.
 		 */
-		if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) ||
-		    intel_pstate_hwp_is_enabled()) {
+		if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) || hwp_forced) {
 			hwp_active++;
 			hwp_mode_bdw = id->driver_data;
 			intel_pstate.attr = hwp_cpufreq_attrs;
@@ -3235,7 +3238,11 @@ static int __init intel_pstate_init(void)
 
 			goto hwp_cpu_matched;
 		}
+		pr_info("HWP not enabled\n");
 	} else {
+		if (no_load)
+			return -ENODEV;
+
 		id = x86_match_cpu(intel_pstate_cpu_ids);
 		if (!id) {
 			pr_info("CPU model not supported\n");
@@ -3314,10 +3321,9 @@ static int __init intel_pstate_setup(char *str)
 	else if (!strcmp(str, "passive"))
 		default_driver = &intel_cpufreq;
 
-	if (!strcmp(str, "no_hwp")) {
-		pr_info("HWP disabled\n");
+	if (!strcmp(str, "no_hwp"))
 		no_hwp = 1;
-	}
+
 	if (!strcmp(str, "force"))
 		force_load = 1;
 	if (!strcmp(str, "hwp_only"))
-- 
2.25.1