linux-kernel - [RFC PATCH 6/6] cpufreq/freq_table: Allow decreasing cpuinfo.max

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Message-ID: <20260126101826.94030-7-pierre.gondois@arm.com>
Date: Mon, 26 Jan 2026 11:18:15 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: linux-kernel@...r.kernel.org
Cc: Jie Zhan <zhanjie9@...ilicon.com>,
	zhenglifeng1@...wei.com,
	Ionela Voinescu <ionela.voinescu@....com>,
	Christian Loehle <christian.loehle@....com>,
	sumitg@...dia.com,
	Pierre Gondois <pierre.gondois@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Huang Rui <ray.huang@....com>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>,
	Mario Limonciello <mario.limonciello@....com>,
	Perry Yuan <perry.yuan@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <lenb@...nel.org>,
	Saravana Kannan <saravanak@...nel.org>,
	linux-pm@...r.kernel.org
Subject: [RFC PATCH 6/6] cpufreq/freq_table: Allow decreasing cpuinfo.max_freq

Drivers not using freq. tables update cpuinfo.max_freq in their
.set_boost() callback. E.g. amd-pstate, cppc_cpufreq.
Drivers relying on freq. tables and supporting boost frequencies
rely on cpufreq_frequency_table_cpuinfo(). cpuinfo.max_freq is
only updated if the new maximal value is higher than the previous
one.

Using the scmi-cpufreq driver which relies on freq. tables, enabling
boost will permanently increases the cpuinfo.max_freq value.
This patch allows to lower cpuinfo.max_freq.

Note:
commit 538b0188da46 ("cpufreq: ACPI: Set cpuinfo.max_freq directly
if max boost is known")
favored having cpuinfo.max_freq reporting the maximal boosted
frequency of a CPU instead of the maximal reachable frequency
due to regressions in the frequency reported by cpuinfo.max
and scaling_cur_freq.
As stated above, this is not what most of the other cpufreq driver
do. I assume that the following patch:
commit 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to
cover boost frequencies")
was correct, but might not have tagged the boosted frequency with
the CPUFREQ_BOOST_FREQ flag in the freq. table.

Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 drivers/cpufreq/freq_table.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index 9b37f37c36389..bd08cbe9e9ba3 100644
--- a/drivers/cpufreq/freq_table.c
+++ b/drivers/cpufreq/freq_table.c
@@ -50,12 +50,7 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy)
 	}

 	policy->cpuinfo.min_freq = min_freq;
-	/*
-	 * If the driver has set its own cpuinfo.max_freq above max_freq, leave
-	 * it as is.
-	 */
-	if (policy->cpuinfo.max_freq < max_freq)
-		policy->cpuinfo.max_freq = max_freq;
+	policy->cpuinfo.max_freq = max_freq;

 	if (min_freq == ~0)
 		return -EINVAL;
--
2.43.0