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Wysocki" , Miguel Ojeda , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl Cc: Viresh Kumar , 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 , linux-kernel@vger.kernel.org Subject: [RFC PATCH V2 6/8] rust: Extend cpufreq bindings for driver registration Date: Fri, 7 Jun 2024 14:42:21 +0530 Message-Id: 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 This extends the cpufreq bindings with bindings for registering a driver. Signed-off-by: Viresh Kumar --- rust/kernel/cpufreq.rs | 492 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 490 insertions(+), 2 deletions(-) diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index d5679272e40b..76eba63b6716 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -9,14 +9,16 @@ use crate::{ bindings, clk, cpumask, device::Device, - error::{code::*, from_err_ptr, to_result, Result, VTABLE_DEFAULT_ERROR}, + error::{code::*, from_err_ptr, from_result, to_result, Result, VTABLE_DEFAULT_ERROR}, prelude::*, types::{ARef, ForeignOwnable}, }; use core::{ + cell::UnsafeCell, + marker::{PhantomData, PhantomPinned}, pin::Pin, - ptr::self, + ptr::{self, addr_of_mut}, }; use macros::vtable; @@ -580,3 +582,489 @@ fn register_em(_policy: &mut Policy) { kernel::build_error(VTABLE_DEFAULT_ERROR) } } + +/// Registration of a cpufreq driver. +pub struct Registration { + registered: bool, + drv: UnsafeCell, + _p: PhantomData, + _pin: PhantomPinned, +} + +// 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 {} + +// 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. +#[allow(clippy::non_send_fields_in_send_ty)] +unsafe impl Send for Registration {} + +impl Default for Registration { + fn default() -> Self { + Self::new() + } +} + +impl Registration { + /// Creates new [`Registration`] but does not register it yet. + /// + /// It is allowed to move. + pub fn new() -> Self { + Self { + registered: false, + drv: UnsafeCell::new(bindings::cpufreq_driver::default()), + _pin: PhantomPinned, + _p: PhantomData, + } + } + + /// Registers a cpufreq driver with the rest of the kernel. + pub fn register( + self: Pin<&mut Self>, + name: &'static CStr, + data: T::Data, + flags: u16, + boost: bool, + ) -> Result { + // SAFETY: We never move out of `this`. + let this = unsafe { self.get_unchecked_mut() }; + + if this.registered { + return Err(EINVAL); + } + + let drv = this.drv.get_mut(); + + // Account for the trailing null character. + let len = name.len() + 1; + if len > drv.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] as *const [i8]) }; + drv.name[..len].copy_from_slice(name); + + drv.boost_enabled = boost; + drv.flags = flags; + + // Allocate an array of 3 pointers to be passed to the C code. + let mut attr = Box::new([ptr::null_mut(); 3], GFP_KERNEL)?; + let mut next = 0; + + // SAFETY: The C code returns a valid pointer here, which is again passed to the C code in + // an array. + attr[next] = + unsafe { addr_of_mut!(bindings::cpufreq_freq_attr_scaling_available_freqs) as *mut _ }; + next += 1; + + if boost { + // SAFETY: The C code returns a valid pointer here, which is again passed to the C code + // in an array. + attr[next] = + unsafe { addr_of_mut!(bindings::cpufreq_freq_attr_scaling_boost_freqs) as *mut _ }; + next += 1; + } + attr[next] = ptr::null_mut(); + + // Pass the ownership of the memory block to the C code. This will be freed when + // the [`Registration`] object goes out of scope. + drv.attr = Box::leak(attr) as *mut _; + + // Initialize mandatory callbacks. + drv.init = Some(Self::init_callback); + drv.verify = Some(Self::verify_callback); + + // Initialize optional callbacks. + drv.setpolicy = if T::HAS_SETPOLICY { + Some(Self::setpolicy_callback) + } else { + None + }; + drv.target = if T::HAS_TARGET { + Some(Self::target_callback) + } else { + None + }; + drv.target_index = if T::HAS_TARGET_INDEX { + Some(Self::target_index_callback) + } else { + None + }; + drv.fast_switch = if T::HAS_FAST_SWITCH { + Some(Self::fast_switch_callback) + } else { + None + }; + drv.adjust_perf = if T::HAS_ADJUST_PERF { + Some(Self::adjust_perf_callback) + } else { + None + }; + drv.get_intermediate = if T::HAS_GET_INTERMEDIATE { + Some(Self::get_intermediate_callback) + } else { + None + }; + drv.target_intermediate = if T::HAS_TARGET_INTERMEDIATE { + Some(Self::target_intermediate_callback) + } else { + None + }; + drv.get = if T::HAS_GET { + Some(Self::get_callback) + } else { + None + }; + drv.update_limits = if T::HAS_UPDATE_LIMITS { + Some(Self::update_limits_callback) + } else { + None + }; + drv.bios_limit = if T::HAS_BIOS_LIMIT { + Some(Self::bios_limit_callback) + } else { + None + }; + drv.online = if T::HAS_ONLINE { + Some(Self::online_callback) + } else { + None + }; + drv.offline = if T::HAS_OFFLINE { + Some(Self::offline_callback) + } else { + None + }; + drv.exit = if T::HAS_EXIT { + Some(Self::exit_callback) + } else { + None + }; + drv.suspend = if T::HAS_SUSPEND { + Some(Self::suspend_callback) + } else { + None + }; + drv.resume = if T::HAS_RESUME { + Some(Self::resume_callback) + } else { + None + }; + drv.ready = if T::HAS_READY { + Some(Self::ready_callback) + } else { + None + }; + drv.set_boost = if T::HAS_SET_BOOST { + Some(Self::set_boost_callback) + } else { + None + }; + drv.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 may call few + // callbacks before `cpufreq_register_driver()` returns. + this.set_data(data)?; + + // SAFETY: It is safe to register the driver with the cpufreq core in the C code. + to_result(unsafe { bindings::cpufreq_register_driver(this.drv.get_mut()) })?; + + this.registered = true; + Ok(()) + } + + /// Returns the previous set data for a cpufreq driver. + pub fn data() -> Option<::Borrowed<'static>> { + // SAFETY: The driver data is earlier set by us from [`set_data()`]. + let data = unsafe { bindings::cpufreq_get_driver_data() }; + if data.is_null() { + None + } else { + // SAFETY: The driver data is earlier set by us from [`set_data()`]. + Some(unsafe { D::borrow(data) }) + } + } + + // Sets the data for a cpufreq driver. + fn set_data(&mut self, data: T::Data) -> Result<()> { + let drv = self.drv.get_mut(); + + if drv.driver_data.is_null() { + // Pass the ownership of the data to the foreign interface. + drv.driver_data = ::into_foreign(data) as _; + Ok(()) + } else { + Err(EBUSY) + } + } + + // Clears and returns the data for a cpufreq driver. + fn clear_data(&mut self) -> Option { + let drv = self.drv.get_mut(); + + if drv.driver_data.is_null() { + None + } else { + // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to + // relinquish it now. + let data = Some(unsafe { ::from_foreign(drv.driver_data) }); + drv.driver_data = ptr::null_mut(); + data + } + } +} + +// cpufreq driver callbacks. +impl Registration { + // Policy's init callback. + extern "C" fn init_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + + let data = T::init(&mut policy)?; + policy.set_data(data)?; + Ok(0) + }) + } + + // Policy's exit callback. + extern "C" fn exit_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + + let data = policy.clear_data(); + T::exit(&mut policy, data).map(|_| 0) + }) + } + + // Policy's online callback. + extern "C" fn online_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::online(&mut policy).map(|_| 0) + }) + } + + // Policy's offline callback. + extern "C" fn offline_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::offline(&mut policy).map(|_| 0) + }) + } + + // Policy's suspend callback. + extern "C" fn suspend_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::suspend(&mut policy).map(|_| 0) + }) + } + + // Policy's resume callback. + extern "C" fn resume_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::resume(&mut policy).map(|_| 0) + }) + } + + // Policy's ready callback. + extern "C" fn ready_callback(ptr: *mut bindings::cpufreq_policy) { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::ready(&mut policy); + } + + // Policy's verify callback. + extern "C" fn verify_callback(ptr: *mut bindings::cpufreq_policy_data) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut data = unsafe { PolicyData::from_ptr(ptr) }; + T::verify(&mut data).map(|_| 0) + }) + } + + // Policy's setpolicy callback. + extern "C" fn setpolicy_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::setpolicy(&mut policy).map(|_| 0) + }) + } + + // Policy's target callback. + extern "C" fn target_callback( + ptr: *mut bindings::cpufreq_policy, + target_freq: u32, + relation: u32, + ) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::target(&mut policy, target_freq, Relation::new(relation)?).map(|_| 0) + }) + } + + // Policy's target_index callback. + extern "C" fn target_index_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::target_index(&mut policy, index).map(|_| 0) + }) + } + + // Policy's fast_switch callback. + extern "C" fn fast_switch_callback( + ptr: *mut bindings::cpufreq_policy, + target_freq: u32, + ) -> core::ffi::c_uint { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::fast_switch(&mut policy, target_freq) + } + + // Policy's adjust_perf callback. + extern "C" fn adjust_perf_callback(cpu: u32, min_perf: u64, target_perf: u64, capacity: u64) { + if let Some(mut policy) = Policy::from_cpu(cpu).ok() { + T::adjust_perf(&mut policy, min_perf, target_perf, capacity); + } + } + + // Policy's get_intermediate callback. + extern "C" fn get_intermediate_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> core::ffi::c_uint { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::get_intermediate(&mut policy, index) + } + + // Policy's target_intermediate callback. + extern "C" fn target_intermediate_callback( + ptr: *mut bindings::cpufreq_policy, + index: u32, + ) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::target_intermediate(&mut policy, index).map(|_| 0) + }) + } + + // Policy's get callback. + extern "C" fn get_callback(cpu: u32) -> core::ffi::c_uint { + // SAFETY: Get the policy for a CPU. + Policy::from_cpu(cpu).map_or(0, |mut policy| T::get(&mut policy).map_or(0, |f| f)) + } + + // Policy's update_limit callback. + extern "C" fn update_limits_callback(cpu: u32) { + // SAFETY: Get the policy for a CPU. + if let Some(mut policy) = Policy::from_cpu(cpu).ok() { + T::update_limits(&mut policy); + } + } + + // Policy's bios_limit callback. + extern "C" fn bios_limit_callback(cpu: i32, limit: *mut u32) -> core::ffi::c_int { + from_result(|| { + let mut policy = Policy::from_cpu(cpu as u32)?; + + // SAFETY: The pointer is guaranteed by the C code to be valid. + T::bios_limit(&mut policy, &mut (unsafe { *limit })).map(|_| 0) + }) + } + + // Policy's set_boost callback. + extern "C" fn set_boost_callback( + ptr: *mut bindings::cpufreq_policy, + state: i32, + ) -> core::ffi::c_int { + from_result(|| { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::set_boost(&mut policy, state).map(|_| 0) + }) + } + + // Policy's register_em callback. + extern "C" fn register_em_callback(ptr: *mut bindings::cpufreq_policy) { + // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the + // duration of this call, so it is guaranteed to remain alive for the lifetime of + // `ptr`. + let mut policy = unsafe { Policy::from_ptr(ptr) }; + T::register_em(&mut policy); + } +} + +impl Drop for Registration { + // Removes the registration from the kernel if it has completed successfully before. + fn drop(&mut self) { + let drv = self.drv.get_mut(); + + if self.registered { + // SAFETY: The driver was earlier registered from `register()`. + unsafe { bindings::cpufreq_unregister_driver(drv) }; + } + + // Free the previously leaked memory to the C code. + if !drv.attr.is_null() { + // SAFETY: The pointer was earlier initialized from the result of `Box::leak`. + unsafe { drop(Box::from_raw(drv.attr)) }; + } + + // Free data + drop(self.clear_data()); + } +}