[V10,11/15] rust: cpufreq: Add initial abstractions for cpufreq framework

Message ID	ac6854885277b23f100c6033fab51a080cdb70eb.1744783509.git.viresh.kumar@linaro.org (mailing list archive)
State	New
Delegated to:	viresh kumar
Headers	show Received: from mail-pf1-f171.google.com (mail-pf1-f171.google.com [209.85.210.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1E11239594 for <linux-pm@vger.kernel.org>; Wed, 16 Apr 2025 06:40:35 +0000 (UTC) From: Viresh Kumar <viresh.kumar@linaro.org> To: "Rafael J. Wysocki" <rafael@kernel.org>, Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>, Danilo Krummrich <dakr@redhat.com>, Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>, Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, Benno Lossin <benno.lossin@proton.me>, Andreas Hindborg <a.hindborg@kernel.org>, Alice Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>, Danilo Krummrich <dakr@kernel.org>, Viresh Kumar <viresh.kumar@linaro.org> Cc: linux-pm@vger.kernel.org, Vincent Guittot <vincent.guittot@linaro.org>, Stephen Boyd <sboyd@kernel.org>, Nishanth Menon <nm@ti.com>, rust-for-linux@vger.kernel.org, Manos Pitsidianakis <manos.pitsidianakis@linaro.org>, =?utf-8?q?Alex_Benn?= =?utf-8?q?=C3=A9e?= <alex.bennee@linaro.org>, Joakim Bech <joakim.bech@linaro.org>, Rob Herring <robh@kernel.org>, Yury Norov <yury.norov@gmail.com>, Burak Emir <bqe@google.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Russell King <linux@armlinux.org.uk>, linux-clk@vger.kernel.org, Michael Turquette <mturquette@baylibre.com>, linux-kernel@vger.kernel.org Subject: [PATCH V10 11/15] rust: cpufreq: Add initial abstractions for cpufreq framework Date: Wed, 16 Apr 2025 12:09:28 +0530 Message-Id: <ac6854885277b23f100c6033fab51a080cdb70eb.1744783509.git.viresh.kumar@linaro.org> In-Reply-To: <cover.1744783509.git.viresh.kumar@linaro.org> References: <cover.1744783509.git.viresh.kumar@linaro.org> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	Rust abstractions for clk, cpumask, cpufreq, OPP \| expand [V10,00/15] Rust abstractions for clk, cpumask, cpufreq, OPP [V10,01/15] rust: cpumask: Add few more helpers [V10,02/15] rust: cpumask: Add initial abstractions [V10,03/15] MAINTAINERS: Add entry for Rust cpumask API [V10,04/15] rust: clk: Add helpers for Rust code [V10,05/15] rust: clk: Add initial abstractions [V10,06/15] rust: macros: enable use of hyphens in module names [V10,07/15] rust: cpu: Add from_cpu() [V10,08/15] rust: opp: Add initial abstractions for OPP framework [V10,09/15] rust: opp: Add abstractions for the OPP table [V10,10/15] rust: opp: Add abstractions for the configuration options [V10,11/15] rust: cpufreq: Add initial abstractions for cpufreq framework [V10,12/15] rust: cpufreq: Extend abstractions for policy and driver ops [V10,13/15] rust: cpufreq: Extend abstractions for driver registration [V10,14/15] rust: opp: Extend OPP abstractions with cpufreq support [V10,15/15] cpufreq: Add Rust-based cpufreq-dt driver

diff --git a/MAINTAINERS b/MAINTAINERS index 931e418f89ed..aa56eacbda71 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6142,6 +6142,7 @@ F: drivers/cpufreq/ F: include/linux/cpufreq.h F: include/linux/sched/cpufreq.h F: kernel/sched/cpufreq*.c +F: rust/kernel/cpufreq.rs F: tools/testing/selftests/cpufreq/ CPU HOTPLUG diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 529f22891e0b..7c1d78f68076 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -12,6 +12,7 @@ #include <linux/blkdev.h> #include <linux/clk.h> #include <linux/cpu.h> +#include <linux/cpufreq.h> #include <linux/cpumask.h> #include <linux/cred.h> #include <linux/device/faux.h> diff --git a/rust/helpers/cpufreq.c b/rust/helpers/cpufreq.c new file mode 100644 index 000000000000..7c1343c4d65e --- /dev/null +++ b/rust/helpers/cpufreq.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/cpufreq.h> + +#ifdef CONFIG_CPU_FREQ +void rust_helper_cpufreq_register_em_with_opp(struct cpufreq_policy *policy) +{ + cpufreq_register_em_with_opp(policy); +} +#endif diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index ae595c9cd91b..df1fcfb3adf3 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -12,6 +12,7 @@ #include "build_assert.c" #include "build_bug.c" #include "clk.c" +#include "cpufreq.c" #include "cpumask.c" #include "cred.c" #include "device.c" diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs new file mode 100644 index 000000000000..d9face425d47 --- /dev/null +++ b/rust/kernel/cpufreq.rs @@ -0,0 +1,348 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! CPU frequency scaling. +//! +//! This module provides rust abstractions for interacting with the cpufreq subsystem. +//! +//! C header: [`include/linux/cpufreq.h`](srctree/include/linux/cpufreq.h) +//! +//! Reference: <https://docs.kernel.org/admin-guide/pm/cpufreq.html> + +use crate::{ + error::{code::*, to_result, Result}, + ffi::c_ulong, + prelude::*, +}; + +use core::{ + pin::Pin, +}; + +/// Default transition latency value in nanoseconds. +pub const ETERNAL_LATENCY_NS: u32 = bindings::CPUFREQ_ETERNAL as u32; + +/// CPU frequency driver flags. +pub mod flags { + /// Driver needs to update internal limits even if frequency remains unchanged. + pub const NEED_UPDATE_LIMITS: u16 = 1 << 0; + + /// Platform where constants like `loops_per_jiffy` are unaffected by frequency changes. + pub const CONST_LOOPS: u16 = 1 << 1; + + /// Register driver as a thermal cooling device automatically. + pub const IS_COOLING_DEV: u16 = 1 << 2; + + /// Supports multiple clock domains with per-policy governors in `cpu/cpuN/cpufreq/`. + pub const HAVE_GOVERNOR_PER_POLICY: u16 = 1 << 3; + + /// Allows post-change notifications outside of the `target()` routine. + pub const ASYNC_NOTIFICATION: u16 = 1 << 4; + + /// Ensure CPU starts at a valid frequency from the driver's freq-table. + pub const NEED_INITIAL_FREQ_CHECK: u16 = 1 << 5; + + /// Disallow governors with `dynamic_switching` capability. + pub const NO_AUTO_DYNAMIC_SWITCHING: u16 = 1 << 6; +} + +// Relations from the C code. +const CPUFREQ_RELATION_L: u32 = 0; +const CPUFREQ_RELATION_H: u32 = 1; +const CPUFREQ_RELATION_C: u32 = 2; + +// Can be used with any of the above values. +const CPUFREQ_RELATION_E: u32 = 1 << 2; + +/// CPU frequency selection relations. +/// +/// CPU frequency selection relations, each optionally marked as "efficient". +#[derive(Copy, Clone, Debug, Eq, PartialEq)] +pub enum Relation { + /// Select the lowest frequency at or above target. + Low(bool), + /// Select the highest frequency below or at target. + High(bool), + /// Select the closest frequency to the target. + Close(bool), +} + +impl Relation { + // Construct from a C-compatible `u32` value. + fn new(val: u32) -> Result<Self> { + let efficient = val & CPUFREQ_RELATION_E != 0; + + Ok(match val & !CPUFREQ_RELATION_E { + CPUFREQ_RELATION_L => Self::Low(efficient), + CPUFREQ_RELATION_H => Self::High(efficient), + CPUFREQ_RELATION_C => Self::Close(efficient), + _ => return Err(EINVAL), + }) + } +} + +impl From<Relation> for u32 { + // Convert to a C-compatible `u32` value. + fn from(rel: Relation) -> Self { + let (mut val, efficient) = match rel { + Relation::Low(e) => (CPUFREQ_RELATION_L, e), + Relation::High(e) => (CPUFREQ_RELATION_H, e), + Relation::Close(e) => (CPUFREQ_RELATION_C, e), + }; + + if efficient { + val |= CPUFREQ_RELATION_E; + } + + val + } +} + +/// Policy data. +/// +/// Rust abstraction for the C `struct cpufreq_policy_data`. +/// +/// # Invariants +/// +/// A [`PolicyData`] instance always corresponds to a valid C `struct cpufreq_policy_data`. +/// +/// The callers must ensure that the `struct cpufreq_policy_data` is valid for access and remains +/// valid for the lifetime of the returned reference. +#[repr(transparent)] +pub struct PolicyData(Opaque<bindings::cpufreq_policy_data>); + +impl PolicyData { + /// Creates a mutable reference to an existing `struct cpufreq_policy_data` pointer. + /// + /// # Safety + /// + /// The caller must ensure that `ptr` is valid for writing and remains valid for the lifetime + /// of the returned reference. + #[inline] + pub unsafe fn from_raw_mut<'a>(ptr: *mut bindings::cpufreq_policy_data) -> &'a mut Self { + // SAFETY: Guaranteed by the safety requirements of the function. + // + // INVARIANT: The caller ensures that `ptr` is valid for writing and remains valid for the + // lifetime of the returned reference. + unsafe { &mut *ptr.cast() } + } + + /// Returns a raw pointer to the underlying C `cpufreq_policy_data`. + #[inline] + pub fn as_raw(&self) -> *mut bindings::cpufreq_policy_data { + let this: *const Self = self; + this.cast_mut().cast() + } + + /// Wrapper for `cpufreq_generic_frequency_table_verify`. + #[inline] + pub fn generic_verify(&self) -> Result<()> { + // SAFETY: By the type invariant, the pointer stored in `self` is valid. + to_result(unsafe { bindings::cpufreq_generic_frequency_table_verify(self.as_raw()) }) + } +} + +/// CPU frequency table. +/// +/// Rust abstraction for the C `struct cpufreq_frequency_table`. +/// +/// # Invariants +/// +/// A [`Table`] instance always corresponds to a valid C `struct cpufreq_frequency_table`. +/// +/// The callers must ensure that the `struct cpufreq_frequency_table` is valid for access and +/// remains valid for the lifetime of the returned reference. +/// +/// ## Examples +/// +/// The following example demonstrates how to read a frequency value from [`Table`]. +/// +/// ``` +/// use kernel::cpufreq::Policy; +/// +/// fn show_freq(policy: &Policy) { +/// let table = policy.freq_table().unwrap(); +/// +/// // SAFETY: The index values passed are correct. +/// unsafe { +/// pr_info!("The frequency at index 0 is: {:?}\n", table.freq(0).unwrap()); +/// pr_info!("The flags at index 0 is: {}\n", table.flags(0)); +/// pr_info!("The data at index 0 is: {}\n", table.data(0)); +/// } +/// } +/// ``` +#[allow(dead_code)] +#[repr(transparent)] +pub struct Table(Opaque<bindings::cpufreq_frequency_table>); + +impl Table { + /// Creates a reference to an existing C `struct cpufreq_frequency_table` pointer. + /// + /// # Safety + /// + /// The caller must ensure that `ptr` is valid for reading and remains valid for the lifetime + /// of the returned reference. + #[inline] + pub unsafe fn from_raw<'a>(ptr: *const bindings::cpufreq_frequency_table) -> &'a Self { + // SAFETY: Guaranteed by the safety requirements of the function. + // + // INVARIANT: The caller ensures that `ptr` is valid for reading and remains valid for the + // lifetime of the returned reference. + unsafe { &*ptr.cast() } + } + + /// Returns the raw mutable pointer to the C `struct cpufreq_frequency_table`. + #[inline] + pub fn as_raw(&self) -> *mut bindings::cpufreq_frequency_table { + let this: *const Self = self; + this.cast_mut().cast() + } + + /// Returns frequency at `index` in the [`Table`]. + /// + /// # Safety + /// + /// The caller must ensure that `index` corresponds to a valid table entry. + #[inline] + pub unsafe fn freq(&self, index: usize) -> Result<Hertz> { + // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is + // guaranteed to be valid by the safety requirements of the function. + Ok(Hertz::from_khz(unsafe { + (*self.as_raw().add(index)).frequency.try_into()? + })) + } + + /// Returns flags at `index` in the [`Table`]. + /// + /// # Safety + /// + /// The caller must ensure that `index` corresponds to a valid table entry. + #[inline] + pub unsafe fn flags(&self, index: usize) -> u32 { + // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is + // guaranteed to be valid by the safety requirements of the function. + unsafe { (*self.as_raw().add(index)).flags } + } + + /// Returns data at `index` in the [`Table`]. + /// + /// # Safety + /// + /// The caller must ensure that `index` corresponds to a valid table entry. + #[inline] + pub unsafe fn data(&self, index: usize) -> u32 { + // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is + // guaranteed to be valid by the safety requirements of the function. + unsafe { (*self.as_raw().add(index)).driver_data } + } +} + +/// CPU frequency table owned and pinned in memory, created from a [`TableBuilder`]. +pub struct TableBox { + #[allow(dead_code)] + entries: Pin<KVec<bindings::cpufreq_frequency_table>>, +} + +impl TableBox { + /// Constructs a new [`TableBox`] from a [`KVec`] of entries. + /// + /// # Errors + /// + /// Returns `EINVAL` if the entries list is empty. + #[inline] + fn new(entries: KVec<bindings::cpufreq_frequency_table>) -> Result<Self> { + if entries.is_empty() { + return Err(EINVAL); + } + + Ok(Self { + // Pin the entries to memory, since we are passing its pointer to the C code. + entries: Pin::new(entries), + }) + } + + /// Returns a raw pointer to the underlying C `cpufreq_frequency_table`. + #[inline] + fn as_raw(&self) -> *const bindings::cpufreq_frequency_table { + // The pointer is valid until the table gets dropped. + self.entries.as_ptr() + } +} + +impl Deref for TableBox { + type Target = Table; + + fn deref(&self) -> &Self::Target { + // SAFETY: The caller owns TableBox, it is safe to deref. + unsafe { Self::Target::from_raw(self.as_raw()) } + } +} + +/// CPU frequency table builder. +/// +/// This is used by the CPU frequency drivers to build a frequency table dynamically. +/// +/// ## Examples +/// +/// The following example demonstrates how to create a CPU frequency table. +/// +/// ``` +/// use kernel::cpufreq::TableBuilder; +/// use kernel::clk::Hertz; +/// +/// let mut builder = TableBuilder::new(); +/// +/// // Adds few entries to the table. +/// builder.add(Hertz::from_mhz(700), 0, 1).unwrap(); +/// builder.add(Hertz::from_mhz(800), 2, 3).unwrap(); +/// builder.add(Hertz::from_mhz(900), 4, 5).unwrap(); +/// builder.add(Hertz::from_ghz(1), 6, 7).unwrap(); +/// +/// let table = builder.to_table().unwrap(); +/// +/// // SAFETY: The index values passed are correct. +/// unsafe { +/// assert_eq!(table.freq(0), Ok(Hertz::from_mhz(700))); +/// assert_eq!(table.flags(0), 0); +/// assert_eq!(table.data(0), 1); +/// +/// assert_eq!(table.freq(2), Ok(Hertz::from_mhz(900))); +/// assert_eq!(table.flags(2), 4); +/// assert_eq!(table.data(2), 5); +/// } +/// ``` +#[derive(Default)] +#[repr(transparent)] +pub struct TableBuilder { + entries: KVec<bindings::cpufreq_frequency_table>, +} + +impl TableBuilder { + /// Creates a new instance of [`TableBuilder`]. + #[inline] + pub fn new() -> Self { + Self { + entries: KVec::new(), + } + } + + /// Adds a new entry to the table. + pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result<()> { + // Adds the new entry at the end of the vector. + Ok(self.entries.push( + bindings::cpufreq_frequency_table { + flags, + driver_data, + frequency: freq.as_khz() as u32, + }, + GFP_KERNEL, + )?) + } + + /// Consumes the [`TableBuilder`] and returns [`TableBox`]. + pub fn to_table(mut self) -> Result<TableBox> { + // Add last entry to the table. + self.add(Hertz(c_ulong::MAX), 0, 0)?; + + TableBox::new(self.entries) + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 11d333c8c673..871fcdc09b35 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -45,6 +45,8 @@ #[cfg(CONFIG_COMMON_CLK)] pub mod clk; pub mod cpu; +#[cfg(CONFIG_CPU_FREQ)] +pub mod cpufreq; pub mod cpumask; pub mod cred; pub mod device;

[V10,11/15] rust: cpufreq: Add initial abstractions for cpufreq framework

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