Rafael J. Wysocki 509c344cdf cpufreq: Make drivers using CPUFREQ_ETERNAL specify transition latency ... commit f97aef092e upstream. Commit a755d0e2d4 ("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: a755d0e2d4 ("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 <shawnguo@kernel.org> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org> Reviewed-by: Jie Zhan <zhanjie9@hisilicon.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Cc: 6.6+ <stable@vger.kernel.org> # 6.6+ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 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 <shawnguo@kernel.org> # with cpufreq-dt driver Reviewed-by: Qais Yousef <qyousef@layalina.io> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2025-10-19 16:37:00 +02:00
..
bindings	mm/ksm: fix flag-dropping behavior in ksm_madvise	2025-10-15 12:04:19 +02:00
helpers	Rust changes for v6.17	2025-08-03 13:49:10 -07:00
kernel	cpufreq: Make drivers using CPUFREQ_ETERNAL specify transition latency	2025-10-19 16:37:00 +02:00
macros	Rust changes for v6.17	2025-08-03 13:49:10 -07:00
pin-init	pin-init changes for v6.17	2025-07-13 23:05:14 +02:00
uapi	rust: enable clippy::ref_as_ptr lint	2025-06-22 23:09:32 +02:00
.gitignore	rust: support running Rust documentation tests as KUnit ones	2023-07-19 09:32:53 -06:00
.kunitconfig	rust: add kunitconfig	2025-03-19 23:22:21 +01:00
bindgen_parameters	rust: map __kernel_size_t and friends also to usize/isize	2024-11-10 23:58:00 +01:00
build_error.rs	rust: add build_error crate	2022-12-04 01:59:16 +01:00
compiler_builtins.rs	ARM: 9441/1: rust: Enable Rust support for ARMv7	2025-03-26 13:31:16 +00:00
exports.c	rust: exports: improve grammar in commentary	2024-10-21 17:35:33 +02:00
ffi.rs	rust: use absolute paths in macros referencing core and kernel	2025-05-23 00:12:14 +02:00
Makefile	rust: kbuild: clean output before running rustdoc	2025-08-12 21:10:50 +02:00