From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC52F3370FB; Fri, 17 Oct 2025 15:27:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760714857; cv=none; b=JEysA6Ugy/iyKshTGYR5ceaJ6jWO5Xcgx3omTtAq/blQ5AlmVaSypbnuG5AFpa1PvhX4c8E5x63v5KahRLI1uHC88G8BGMBccyyIWawjMkOs6iO931lv5L8BZl2PO6SJ3Ato4j6G1BmMrxflM0+FMLXGESxjO5z2stluG4aB+LE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760714857; c=relaxed/simple; bh=DtOQElQFSPY1dBSQbhDiyJ9BmqWCvYj8Q2A/ooYxdv8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=B3pGtAxOImdKOZmg9tPB8AJf9000b6x0up0X3S8ANTTbbIjrswOoZ5J+LuozaCsCXcXYJuY8dj2cOPeAaU0512Ukh8U8IpvdwQzmP2c7vceU7Z7RYBt1V9SW1ZQUvq8T2HRlgWPWekDLW04DryB1iXR/aXsLOIPGjRdOFIZS4II= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Oj1UMwzu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Oj1UMwzu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FF6CC4CEE7; Fri, 17 Oct 2025 15:27:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760714856; bh=DtOQElQFSPY1dBSQbhDiyJ9BmqWCvYj8Q2A/ooYxdv8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Oj1UMwzug6F0rth/btfDzRKf3RzeibW3//izqHGidIfjEdgDDiRae85uJNznculib 9JIqihYxjcSOS53KDVS4dl0xi/PVr+s43ZjhCAr99waqzRZD3R0Tm8rSoy5aLsy3gg iQTb/G4aGi9bBLKj2rvlPdkFprIavRuJGF63xHP0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Shawn Guo , "Mario Limonciello (AMD)" , Jie Zhan , Viresh Kumar , "Rafael J. Wysocki" , Qais Yousef Subject: [PATCH 6.17 013/371] cpufreq: Make drivers using CPUFREQ_ETERNAL specify transition latency Date: Fri, 17 Oct 2025 16:49:48 +0200 Message-ID: <20251017145202.276530039@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251017145201.780251198@linuxfoundation.org> References: <20251017145201.780251198@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rafael J. Wysocki commit f97aef092e199c10a3da96ae79b571edd5362faa upstream. Commit a755d0e2d41b ("cpufreq: Honour transition_latency over transition_delay_us") caused platforms where cpuinfo.transition_latency is CPUFREQ_ETERNAL to get a very large transition latency whereas previously it had been capped at 10 ms (and later at 2 ms). This led to a user-observable regression between 6.6 and 6.12 as described by Shawn: "The dbs sampling_rate was 10000 us on 6.6 and suddently becomes 6442450 us (4294967295 / 1000 * 1.5) on 6.12 for these platforms because the default transition delay was dropped [...]. It slows down dbs governor's reacting to CPU loading change dramatically. Also, as transition_delay_us is used by schedutil governor as rate_limit_us, it shows a negative impact on device idle power consumption, because the device gets slightly less time in the lowest OPP." Evidently, the expectation of the drivers using CPUFREQ_ETERNAL as cpuinfo.transition_latency was that it would be capped by the core, but they may as well return a default transition latency value instead of CPUFREQ_ETERNAL and the core need not do anything with it. Accordingly, introduce CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS and make all of the drivers in question use it instead of CPUFREQ_ETERNAL. Also update the related Rust binding. Fixes: a755d0e2d41b ("cpufreq: Honour transition_latency over transition_delay_us") Closes: https://lore.kernel.org/linux-pm/20250922125929.453444-1-shawnguo2@yeah.net/ Reported-by: Shawn Guo Reviewed-by: Mario Limonciello (AMD) Reviewed-by: Jie Zhan Acked-by: Viresh Kumar Cc: 6.6+ # 6.6+ Signed-off-by: Rafael J. Wysocki Link: https://patch.msgid.link/2264949.irdbgypaU6@rafael.j.wysocki [ rjw: Fix typo in new symbol name, drop redundant type cast from Rust binding ] Tested-by: Shawn Guo # with cpufreq-dt driver Reviewed-by: Qais Yousef Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/cpufreq/cpufreq-dt.c | 2 +- drivers/cpufreq/imx6q-cpufreq.c | 2 +- drivers/cpufreq/mediatek-cpufreq-hw.c | 2 +- drivers/cpufreq/rcpufreq_dt.rs | 2 +- drivers/cpufreq/scmi-cpufreq.c | 2 +- drivers/cpufreq/scpi-cpufreq.c | 2 +- drivers/cpufreq/spear-cpufreq.c | 2 +- include/linux/cpufreq.h | 3 +++ rust/kernel/cpufreq.rs | 7 ++++--- 9 files changed, 14 insertions(+), 10 deletions(-) --- a/drivers/cpufreq/cpufreq-dt.c +++ b/drivers/cpufreq/cpufreq-dt.c @@ -104,7 +104,7 @@ static int cpufreq_init(struct cpufreq_p transition_latency = dev_pm_opp_get_max_transition_latency(cpu_dev); if (!transition_latency) - transition_latency = CPUFREQ_ETERNAL; + transition_latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; cpumask_copy(policy->cpus, priv->cpus); policy->driver_data = priv; --- a/drivers/cpufreq/imx6q-cpufreq.c +++ b/drivers/cpufreq/imx6q-cpufreq.c @@ -442,7 +442,7 @@ soc_opp_out: } if (of_property_read_u32(np, "clock-latency", &transition_latency)) - transition_latency = CPUFREQ_ETERNAL; + transition_latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; /* * Calculate the ramp time for max voltage change in the --- a/drivers/cpufreq/mediatek-cpufreq-hw.c +++ b/drivers/cpufreq/mediatek-cpufreq-hw.c @@ -238,7 +238,7 @@ static int mtk_cpufreq_hw_cpu_init(struc latency = readl_relaxed(data->reg_bases[REG_FREQ_LATENCY]) * 1000; if (!latency) - latency = CPUFREQ_ETERNAL; + latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; policy->cpuinfo.transition_latency = latency; policy->fast_switch_possible = true; --- a/drivers/cpufreq/rcpufreq_dt.rs +++ b/drivers/cpufreq/rcpufreq_dt.rs @@ -123,7 +123,7 @@ impl cpufreq::Driver for CPUFreqDTDriver let mut transition_latency = opp_table.max_transition_latency_ns() as u32; if transition_latency == 0 { - transition_latency = cpufreq::ETERNAL_LATENCY_NS; + transition_latency = cpufreq::DEFAULT_TRANSITION_LATENCY_NS; } policy --- a/drivers/cpufreq/scmi-cpufreq.c +++ b/drivers/cpufreq/scmi-cpufreq.c @@ -294,7 +294,7 @@ static int scmi_cpufreq_init(struct cpuf latency = perf_ops->transition_latency_get(ph, domain); if (!latency) - latency = CPUFREQ_ETERNAL; + latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; policy->cpuinfo.transition_latency = latency; --- a/drivers/cpufreq/scpi-cpufreq.c +++ b/drivers/cpufreq/scpi-cpufreq.c @@ -157,7 +157,7 @@ static int scpi_cpufreq_init(struct cpuf latency = scpi_ops->get_transition_latency(cpu_dev); if (!latency) - latency = CPUFREQ_ETERNAL; + latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; policy->cpuinfo.transition_latency = latency; --- a/drivers/cpufreq/spear-cpufreq.c +++ b/drivers/cpufreq/spear-cpufreq.c @@ -182,7 +182,7 @@ static int spear_cpufreq_probe(struct pl if (of_property_read_u32(np, "clock-latency", &spear_cpufreq.transition_latency)) - spear_cpufreq.transition_latency = CPUFREQ_ETERNAL; + spear_cpufreq.transition_latency = CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; cnt = of_property_count_u32_elems(np, "cpufreq_tbl"); if (cnt <= 0) { --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -32,6 +32,9 @@ */ #define CPUFREQ_ETERNAL (-1) + +#define CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS NSEC_PER_MSEC + #define CPUFREQ_NAME_LEN 16 /* Print length for names. Extra 1 space for accommodating '\n' in prints */ #define CPUFREQ_NAME_PLEN (CPUFREQ_NAME_LEN + 1) --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -39,7 +39,8 @@ use macros::vtable; const CPUFREQ_NAME_LEN: usize = bindings::CPUFREQ_NAME_LEN as usize; /// Default transition latency value in nanoseconds. -pub const ETERNAL_LATENCY_NS: u32 = bindings::CPUFREQ_ETERNAL as u32; +pub const DEFAULT_TRANSITION_LATENCY_NS: u32 = + bindings::CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS; /// CPU frequency driver flags. pub mod flags { @@ -400,13 +401,13 @@ impl TableBuilder { /// The following example demonstrates how to create a CPU frequency table. /// /// ``` -/// use kernel::cpufreq::{ETERNAL_LATENCY_NS, Policy}; +/// use kernel::cpufreq::{DEFAULT_TRANSITION_LATENCY_NS, Policy}; /// /// fn update_policy(policy: &mut Policy) { /// policy /// .set_dvfs_possible_from_any_cpu(true) /// .set_fast_switch_possible(true) -/// .set_transition_latency_ns(ETERNAL_LATENCY_NS); +/// .set_transition_latency_ns(DEFAULT_TRANSITION_LATENCY_NS); /// /// pr_info!("The policy details are: {:?}\n", (policy.cpu(), policy.cur())); /// }