linux-kernel - [PATCH v1] cpufreq: intel_pstate: Always use HWP_DESIRED

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Message-ID: <6173276.lOV4Wx5bFT@rjwysocki.net>
Date: Mon, 16 Jun 2025 20:19:19 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Shashank Balaji <shashank.mahadasyam@...y.com>,
 Russell Haley <yumpusamongus@...il.com>
Subject:
 [PATCH v1] cpufreq: intel_pstate: Always use HWP_DESIRED_PERF in passive mode

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

In the passive mode, intel_cpufreq_update_pstate() sets HWP_MIN_PERF in
accordance with the target frequency to ensure delivering adequate
performance, but it sets HWP_DESIRED_PERF to 0, so the processor has no
indication that the desired performance level is actually equal to the
floor one.  This may cause it to choose a performance point way above
the desired level.

Moreover, this is inconsistent with intel_cpufreq_adjust_perf() which
actually sets HWP_DESIRED_PERF in accordance with the target performance
value.

Address this by adjusting intel_cpufreq_update_pstate() to pass
target_pstate as both the minimum and the desired performance levels
to intel_cpufreq_hwp_update().

Fixes: a365ab6b9dfb ("cpufreq: intel_pstate: Implement the ->adjust_perf() callback")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/intel_pstate.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3249,8 +3249,8 @@
 		int max_pstate = policy->strict_target ?
 					target_pstate : cpu->max_perf_ratio;

-		intel_cpufreq_hwp_update(cpu, target_pstate, max_pstate, 0,
-					 fast_switch);
+		intel_cpufreq_hwp_update(cpu, target_pstate, max_pstate,
+					 target_pstate, fast_switch);
 	} else if (target_pstate != old_pstate) {
 		intel_cpufreq_perf_ctl_update(cpu, target_pstate, fast_switch);
 	}