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Wysocki" , Miguel Ojeda , Danilo Krummrich , Viresh Kumar , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?B?= =?utf-8?q?j=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich Cc: linux-pm@vger.kernel.org, Vincent Guittot , Stephen Boyd , Nishanth Menon , rust-for-linux@vger.kernel.org, Manos Pitsidianakis , Erik Schilling , =?utf-8?q?Alex_Benn=C3=A9e?= , Joakim Bech , Rob Herring , Yury Norov , Burak Emir , Rasmus Villemoes , Russell King , linux-clk@vger.kernel.org, Michael Turquette , linux-kernel@vger.kernel.org Subject: [PATCH V9 15/17] rust: cpufreq: Extend abstractions for driver registration Date: Fri, 11 Apr 2025 16:25:14 +0530 Message-Id: <2f7a1331ad513b94fb47c05bf1d0f5c3fa803858.1744366572.git.viresh.kumar@linaro.org> X-Mailer: git-send-email 2.31.1.272.g89b43f80a514 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Extend the cpufreq abstractions to support driver registration from Rust. Signed-off-by: Viresh Kumar --- rust/kernel/cpufreq.rs | 530 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 528 insertions(+), 2 deletions(-) diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index 3e9ded655d46..4194b9558413 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -13,7 +13,8 @@ clk::{Clk, Hertz}, cpumask, device::Device, - error::{code::*, from_err_ptr, to_result, Result, VTABLE_DEFAULT_ERROR}, + devres::Devres, + error::{code::*, from_err_ptr, from_result, to_result, Result, VTABLE_DEFAULT_ERROR}, ffi::c_ulong, prelude::*, types::ForeignOwnable, @@ -21,9 +22,11 @@ }; use core::{ + cell::UnsafeCell, + marker::PhantomData, ops::{Deref, DerefMut}, pin::Pin, - ptr::self, + ptr, }; use macros::vtable; @@ -792,3 +795,526 @@ fn register_em(_policy: &mut Policy) { build_error!(VTABLE_DEFAULT_ERROR) } } + +/// CPU frequency driver Registration. +/// +/// ## Examples +/// +/// The following example demonstrates how to register a cpufreq driver. +/// +/// ``` +/// use kernel::{ +/// c_str, +/// cpu, cpufreq, +/// device::Device, +/// macros::vtable, +/// sync::Arc, +/// }; +/// struct FooDevice; +/// +/// #[derive(Default)] +/// struct FooDriver; +/// +/// #[vtable] +/// impl cpufreq::Driver for FooDriver { +/// type Data = (); +/// type PData = Arc; +/// +/// fn init(policy: &mut cpufreq::Policy) -> Result { +/// // Initialize here +/// Ok(Arc::new(FooDevice, GFP_KERNEL)?) +/// } +/// +/// fn exit(_policy: &mut cpufreq::Policy, _data: Option) -> Result<()> { +/// Ok(()) +/// } +/// +/// fn suspend(policy: &mut cpufreq::Policy) -> Result<()> { +/// policy.generic_suspend() +/// } +/// +/// fn verify(data: &mut cpufreq::PolicyData) -> Result<()> { +/// data.generic_verify() +/// } +/// +/// fn target_index(policy: &mut cpufreq::Policy, index: u32) -> Result<()> { +/// // Update CPU frequency +/// Ok(()) +/// } +/// +/// fn get(policy: &mut cpufreq::Policy) -> Result { +/// policy.generic_get() +/// } +/// } +/// +/// fn foo_probe(dev: &Device) { +/// cpufreq::Registration::::new_foreign_owned( +/// dev, +/// c_str!("cpufreq-foo"), +/// (), +/// cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV, +/// true, +/// ).unwrap(); +/// } +/// ``` +pub struct Registration { + drv: KBox>, + _p: PhantomData, +} + +// SAFETY: `Registration` doesn't offer any methods or access to fields when shared between threads +// or CPUs, so it is safe to share it. +unsafe impl Sync for Registration {} + +#[allow(clippy::non_send_fields_in_send_ty)] +// SAFETY: Registration with and unregistration from the cpufreq subsystem can happen from any +// thread. Additionally, `T::Data` (which is dropped during unregistration) is `Send`, so it is +// okay to move `Registration` to different threads. +unsafe impl Send for Registration {} + +impl Registration { + /// Registers a CPU frequency driver with the cpufreq core. + pub fn new(name: &'static CStr, data: T::Data, flags: u16, boost: bool) -> Result { + // Required due to Rust 1.82's stricter handling of `unsafe` in mutable statics. The + // `unsafe` blocks aren't required anymore with later versions. + #![allow(unused_unsafe)] + + let mut drv = KBox::new( + UnsafeCell::new(bindings::cpufreq_driver::default()), + GFP_KERNEL, + )?; + let drv_ref = drv.get_mut(); + + // Account for the trailing null byte. + let len = name.len() + 1; + if len > drv_ref.name.len() { + return Err(EINVAL); + }; + + // SAFETY: `name` is a valid `CStr`, and we are copying it to an array of equal or larger + // size. + let name = unsafe { &*(name.as_bytes_with_nul() as *const [u8]) }; + drv_ref.name[..len].copy_from_slice(name); + + drv_ref.boost_enabled = boost; + drv_ref.flags = flags; + + // Initialize mandatory callbacks. + drv_ref.init = Some(Self::init_callback); + drv_ref.verify = Some(Self::verify_callback); + + // Initialize optional callbacks based on the traits of `T`. + drv_ref.setpolicy = if T::HAS_SETPOLICY { + Some(Self::setpolicy_callback) + } else { + None + }; + drv_ref.target = if T::HAS_TARGET { + Some(Self::target_callback) + } else { + None + }; + drv_ref.target_index = if T::HAS_TARGET_INDEX { + Some(Self::target_index_callback) + } else { + None + }; + drv_ref.fast_switch = if T::HAS_FAST_SWITCH { + Some(Self::fast_switch_callback) + } else { + None + }; + drv_ref.adjust_perf = if T::HAS_ADJUST_PERF { + Some(Self::adjust_perf_callback) + } else { + None + }; + drv_ref.get_intermediate = if T::HAS_GET_INTERMEDIATE { + Some(Self::get_intermediate_callback) + } else { + None + }; + drv_ref.target_intermediate = if T::HAS_TARGET_INTERMEDIATE { + Some(Self::target_intermediate_callback) + } else { + None + }; + drv_ref.get = if T::HAS_GET { + Some(Self::get_callback) + } else { + None + }; + drv_ref.update_limits = if T::HAS_UPDATE_LIMITS { + Some(Self::update_limits_callback) + } else { + None + }; + drv_ref.bios_limit = if T::HAS_BIOS_LIMIT { + Some(Self::bios_limit_callback) + } else { + None + }; + drv_ref.online = if T::HAS_ONLINE { + Some(Self::online_callback) + } else { + None + }; + drv_ref.offline = if T::HAS_OFFLINE { + Some(Self::offline_callback) + } else { + None + }; + drv_ref.exit = if T::HAS_EXIT { + Some(Self::exit_callback) + } else { + None + }; + drv_ref.suspend = if T::HAS_SUSPEND { + Some(Self::suspend_callback) + } else { + None + }; + drv_ref.resume = if T::HAS_RESUME { + Some(Self::resume_callback) + } else { + None + }; + drv_ref.ready = if T::HAS_READY { + Some(Self::ready_callback) + } else { + None + }; + drv_ref.set_boost = if T::HAS_SET_BOOST { + Some(Self::set_boost_callback) + } else { + None + }; + drv_ref.register_em = if T::HAS_REGISTER_EM { + Some(Self::register_em_callback) + } else { + None + }; + + // Set driver data before registering the driver, as the cpufreq core calls few callbacks + // before `cpufreq_register_driver` returns. + Self::set_data(drv_ref, data)?; + + // SAFETY: It is safe to register the driver with the cpufreq core in the kernel C code. + to_result(unsafe { bindings::cpufreq_register_driver(drv_ref) })?; + + Ok(Self { + drv, + _p: PhantomData, + }) + } + + /// Same as [`Registration::new`], but does not return a [`Registration`] instance. + /// + /// Instead the [`Registration`] is owned by [`Devres`] and will be revoked / dropped, once the + /// device is detached. + pub fn new_foreign_owned( + dev: &Device, + name: &'static CStr, + data: T::Data, + flags: u16, + boost: bool, + ) -> Result<()> { + Devres::new_foreign_owned(dev, Self::new(name, data, flags, boost)?, GFP_KERNEL)?; + Ok(()) + } + + // Sets the `Data` for the CPU frequency driver. + fn set_data(drv: &mut bindings::cpufreq_driver, data: T::Data) -> Result<()> { + if drv.driver_data.is_null() { + // Transfer the ownership of the data to the C code. + drv.driver_data = ::into_foreign(data) as _; + Ok(()) + } else { + Err(EBUSY) + } + } + + /// Returns borrowed `Data` previously set for the CPU frequency driver. + pub fn data(&mut self) -> Option<::Borrowed<'static>> { + let drv = self.drv.get_mut(); + + if drv.driver_data.is_null() { + None + } else { + // SAFETY: The data is earlier set by us from `set_data`. + Some(unsafe { ::borrow(drv.driver_data) }) + } + } + + // Clears and returns the `Data` for the CPU frequency driver. + fn clear_data(&mut self) -> Option { + let drv = self.drv.get_mut(); + + if drv.driver_data.is_null() { + None + } else { + // SAFETY: The data is earlier set by us from `set_data`. + let data = Some(unsafe { ::from_foreign(drv.driver_data) }); + drv.driver_data = ptr::null_mut(); + data + } + } +} + +// CPU frequency driver callbacks. +impl Registration { + // Driver's `init` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn init_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + + let data = T::init(policy)?; + policy.set_data(data)?; + Ok(0) + }) + } + + // Driver's `exit` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn exit_callback(ptr: *mut bindings::cpufreq_policy) { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + + let data = policy.clear_data(); + let _ = T::exit(policy, data); + } + + // Driver's `online` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn online_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::online(policy).map(|()| 0) + }) + } + + // Driver's `offline` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn offline_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::offline(policy).map(|()| 0) + }) + } + + // Driver's `suspend` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn suspend_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::suspend(policy).map(|()| 0) + }) + } + + // Driver's `resume` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn resume_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::resume(policy).map(|()| 0) + }) + } + + // Driver's `ready` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn ready_callback(ptr: *mut bindings::cpufreq_policy) { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::ready(policy); + } + + // Driver's `verify` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn verify_callback(ptr: *mut bindings::cpufreq_policy_data) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let data = unsafe { PolicyData::from_raw_mut(ptr) }; + T::verify(data).map(|()| 0) + }) + } + + // Driver's `setpolicy` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn setpolicy_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::setpolicy(policy).map(|()| 0) + }) + } + + // Driver's `target` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn target_callback( + ptr: *mut bindings::cpufreq_policy, + target_freq: u32, + relation: u32, + ) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::target(policy, target_freq, Relation::new(relation)?).map(|()| 0) + }) + } + + // Driver's `target_index` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn target_index_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::target_index(policy, index).map(|()| 0) + }) + } + + // Driver's `fast_switch` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn fast_switch_callback( + ptr: *mut bindings::cpufreq_policy, + target_freq: u32, + ) -> kernel::ffi::c_uint { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::fast_switch(policy, target_freq) + } + + // Driver's `adjust_perf` callback. + extern "C" fn adjust_perf_callback( + cpu: u32, + min_perf: usize, + target_perf: usize, + capacity: usize, + ) { + if let Ok(mut policy) = PolicyCpu::from_cpu(cpu) { + T::adjust_perf(&mut policy, min_perf, target_perf, capacity); + } + } + + // Driver's `get_intermediate` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn get_intermediate_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> kernel::ffi::c_uint { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::get_intermediate(policy, index) + } + + // Driver's `target_intermediate` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn target_intermediate_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::target_intermediate(policy, index).map(|()| 0) + }) + } + + // Driver's `get` callback. + extern "C" fn get_callback(cpu: u32) -> kernel::ffi::c_uint { + PolicyCpu::from_cpu(cpu).map_or(0, |mut policy| T::get(&mut policy).map_or(0, |f| f)) + } + + // Driver's `update_limit` callback. + extern "C" fn update_limits_callback(cpu: u32) { + if let Ok(mut policy) = PolicyCpu::from_cpu(cpu) { + T::update_limits(&mut policy); + } + } + + // Driver's `bios_limit` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn bios_limit_callback(cpu: i32, limit: *mut u32) -> kernel::ffi::c_int { + from_result(|| { + let mut policy = PolicyCpu::from_cpu(cpu as u32)?; + + // SAFETY: `limit` is guaranteed by the C code to be valid. + T::bios_limit(&mut policy, &mut (unsafe { *limit })).map(|()| 0) + }) + } + + // Driver's `set_boost` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn set_boost_callback( + ptr: *mut bindings::cpufreq_policy, + state: i32, + ) -> kernel::ffi::c_int { + from_result(|| { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::set_boost(policy, state).map(|()| 0) + }) + } + + // Driver's `register_em` callback. + // + // SAFETY: Called from C. Inputs must be valid pointers. + extern "C" fn register_em_callback(ptr: *mut bindings::cpufreq_policy) { + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::register_em(policy); + } +} + +impl Drop for Registration { + // Removes the `Registration` from the kernel, if it has initialized successfully earlier. + fn drop(&mut self) { + let drv = self.drv.get_mut(); + + // SAFETY: The driver was earlier registered from `new`. + unsafe { bindings::cpufreq_unregister_driver(drv) }; + + // Free data + drop(self.clear_data()); + } +}