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rust: opp: Add initial abstractions for OPP framework

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Introduce initial Rust abstractions for the Operating Performance Points
(OPP) framework. This includes bindings for `struct dev_pm_opp` and
`struct dev_pm_opp_data`, laying the groundwork for further OPP
integration.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Viresh Kumar 2023-12-18 11:15:13 +05:30
parent 3accb57d56
commit 8f835497b3
4 changed files with 303 additions and 0 deletions
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1
MAINTAINERS
View file

@ -18165,6 +18165,7 @@ F: Documentation/devicetree/bindings/opp/
F: Documentation/power/opp.rst
F: drivers/opp/
F: include/linux/pm_opp.h
F: rust/kernel/opp.rs
OPL4 DRIVER
M: Clemens Ladisch <clemens@ladisch.de>

1
rust/bindings/bindings_helper.h
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@ -30,6 +30,7 @@
#include <linux/phy.h>
#include <linux/pid_namespace.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/poll.h>
#include <linux/property.h>
#include <linux/refcount.h>

2
rust/kernel/lib.rs
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@ -67,6 +67,8 @@ pub mod miscdevice;
#[cfg(CONFIG_NET)]
pub mod net;
pub mod of;
#[cfg(CONFIG_PM_OPP)]
pub mod opp;
pub mod page;
#[cfg(CONFIG_PCI)]
pub mod pci;

299
rust/kernel/opp.rs Normal file
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@ -0,0 +1,299 @@
// SPDX-License-Identifier: GPL-2.0
//! Operating performance points.
//!
//! This module provides rust abstractions for interacting with the OPP subsystem.
//!
//! C header: [`include/linux/pm_opp.h`](srctree/include/linux/pm_opp.h)
//!
//! Reference: <https://docs.kernel.org/power/opp.html>
use crate::{
clk::Hertz,
device::Device,
error::{code::*, to_result, Result},
ffi::c_ulong,
types::{ARef, AlwaysRefCounted, Opaque},
};
use core::ptr;
/// The voltage unit.
///
/// Represents voltage in microvolts, wrapping a [`c_ulong`] value.
///
/// ## Examples
///
/// ```
/// use kernel::opp::MicroVolt;
///
/// let raw = 90500;
/// let volt = MicroVolt(raw);
///
/// assert_eq!(usize::from(volt), raw);
/// assert_eq!(volt, MicroVolt(raw));
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct MicroVolt(pub c_ulong);
impl From<MicroVolt> for c_ulong {
#[inline]
fn from(volt: MicroVolt) -> Self {
volt.0
}
}
/// The power unit.
///
/// Represents power in microwatts, wrapping a [`c_ulong`] value.
///
/// ## Examples
///
/// ```
/// use kernel::opp::MicroWatt;
///
/// let raw = 1000000;
/// let power = MicroWatt(raw);
///
/// assert_eq!(usize::from(power), raw);
/// assert_eq!(power, MicroWatt(raw));
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct MicroWatt(pub c_ulong);
impl From<MicroWatt> for c_ulong {
#[inline]
fn from(power: MicroWatt) -> Self {
power.0
}
}
/// Handle for a dynamically created [`OPP`].
///
/// The associated [`OPP`] is automatically removed when the [`Token`] is dropped.
///
/// ## Examples
///
/// The following example demonstrates how to create an [`OPP`] dynamically.
///
/// ```
/// use kernel::clk::Hertz;
/// use kernel::device::Device;
/// use kernel::error::Result;
/// use kernel::opp::{Data, MicroVolt, Token};
/// use kernel::types::ARef;
///
/// fn create_opp(dev: &ARef<Device>, freq: Hertz, volt: MicroVolt, level: u32) -> Result<Token> {
/// let data = Data::new(freq, volt, level, false);
///
/// // OPP is removed once token goes out of scope.
/// data.add_opp(dev)
/// }
/// ```
pub struct Token {
dev: ARef<Device>,
freq: Hertz,
}
impl Token {
/// Dynamically adds an [`OPP`] and returns a [`Token`] that removes it on drop.
fn new(dev: &ARef<Device>, mut data: Data) -> Result<Self> {
// SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
// requirements.
to_result(unsafe { bindings::dev_pm_opp_add_dynamic(dev.as_raw(), &mut data.0) })?;
Ok(Self {
dev: dev.clone(),
freq: data.freq(),
})
}
}
impl Drop for Token {
fn drop(&mut self) {
// SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
// requirements.
unsafe { bindings::dev_pm_opp_remove(self.dev.as_raw(), self.freq.into()) };
}
}
/// OPP data.
///
/// Rust abstraction for the C `struct dev_pm_opp_data`, used to define operating performance
/// points (OPPs) dynamically.
///
/// ## Examples
///
/// The following example demonstrates how to create an [`OPP`] with [`Data`].
///
/// ```
/// use kernel::clk::Hertz;
/// use kernel::device::Device;
/// use kernel::error::Result;
/// use kernel::opp::{Data, MicroVolt, Token};
/// use kernel::types::ARef;
///
/// fn create_opp(dev: &ARef<Device>, freq: Hertz, volt: MicroVolt, level: u32) -> Result<Token> {
/// let data = Data::new(freq, volt, level, false);
///
/// // OPP is removed once token goes out of scope.
/// data.add_opp(dev)
/// }
/// ```
#[repr(transparent)]
pub struct Data(bindings::dev_pm_opp_data);
impl Data {
/// Creates a new instance of [`Data`].
///
/// This can be used to define a dynamic OPP to be added to a device.
pub fn new(freq: Hertz, volt: MicroVolt, level: u32, turbo: bool) -> Self {
Self(bindings::dev_pm_opp_data {
turbo,
freq: freq.into(),
u_volt: volt.into(),
level,
})
}
/// Adds an [`OPP`] dynamically.
///
/// Returns a [`Token`] that ensures the OPP is automatically removed
/// when it goes out of scope.
#[inline]
pub fn add_opp(self, dev: &ARef<Device>) -> Result<Token> {
Token::new(dev, self)
}
/// Returns the frequency associated with this OPP data.
#[inline]
fn freq(&self) -> Hertz {
Hertz(self.0.freq)
}
}
/// A reference-counted Operating performance point (OPP).
///
/// Rust abstraction for the C `struct dev_pm_opp`.
///
/// # Invariants
///
/// The pointer stored in `Self` is non-null and valid for the lifetime of the [`OPP`].
///
/// Instances of this type are reference-counted. The reference count is incremented by the
/// `dev_pm_opp_get` function and decremented by `dev_pm_opp_put`. The Rust type `ARef<OPP>`
/// represents a pointer that owns a reference count on the [`OPP`].
///
/// A reference to the [`OPP`], &[`OPP`], isn't refcounted by the Rust code.
#[repr(transparent)]
pub struct OPP(Opaque<bindings::dev_pm_opp>);
/// SAFETY: It is okay to send the ownership of [`OPP`] across thread boundaries.
unsafe impl Send for OPP {}
/// SAFETY: It is okay to access [`OPP`] through shared references from other threads because we're
/// either accessing properties that don't change or that are properly synchronised by C code.
unsafe impl Sync for OPP {}
/// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted.
unsafe impl AlwaysRefCounted for OPP {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
unsafe { bindings::dev_pm_opp_get(self.0.get()) };
}
unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
// SAFETY: The safety requirements guarantee that the refcount is nonzero.
unsafe { bindings::dev_pm_opp_put(obj.cast().as_ptr()) }
}
}
impl OPP {
/// Creates an owned reference to a [`OPP`] from a valid pointer.
///
/// The refcount is incremented by the C code and will be decremented by `dec_ref` when the
/// [`ARef`] object is dropped.
///
/// # Safety
///
/// The caller must ensure that `ptr` is valid and the refcount of the [`OPP`] is incremented.
/// The caller must also ensure that it doesn't explicitly drop the refcount of the [`OPP`], as
/// the returned [`ARef`] object takes over the refcount increment on the underlying object and
/// the same will be dropped along with it.
pub unsafe fn from_raw_opp_owned(ptr: *mut bindings::dev_pm_opp) -> Result<ARef<Self>> {
let ptr = ptr::NonNull::new(ptr).ok_or(ENODEV)?;
// SAFETY: The safety requirements guarantee the validity of the pointer.
//
// INVARIANT: The reference-count is decremented when [`OPP`] goes out of scope.
Ok(unsafe { ARef::from_raw(ptr.cast()) })
}
/// Creates a reference to a [`OPP`] from a valid pointer.
///
/// The refcount is not updated by the Rust API unless the returned reference is converted to
/// an [`ARef`] object.
///
/// # Safety
///
/// The caller must ensure that `ptr` is valid and remains valid for the duration of `'a`.
#[inline]
pub unsafe fn from_raw_opp<'a>(ptr: *mut bindings::dev_pm_opp) -> Result<&'a Self> {
// SAFETY: The caller guarantees that the pointer is not dangling and stays valid for the
// duration of 'a. The cast is okay because [`OPP`] is `repr(transparent)`.
Ok(unsafe { &*ptr.cast() })
}
#[inline]
fn as_raw(&self) -> *mut bindings::dev_pm_opp {
self.0.get()
}
/// Returns the frequency of an [`OPP`].
pub fn freq(&self, index: Option<u32>) -> Hertz {
let index = index.unwrap_or(0);
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
Hertz(unsafe { bindings::dev_pm_opp_get_freq_indexed(self.as_raw(), index) })
}
/// Returns the voltage of an [`OPP`].
#[inline]
pub fn voltage(&self) -> MicroVolt {
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
MicroVolt(unsafe { bindings::dev_pm_opp_get_voltage(self.as_raw()) })
}
/// Returns the level of an [`OPP`].
#[inline]
pub fn level(&self) -> u32 {
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
unsafe { bindings::dev_pm_opp_get_level(self.as_raw()) }
}
/// Returns the power of an [`OPP`].
#[inline]
pub fn power(&self) -> MicroWatt {
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
MicroWatt(unsafe { bindings::dev_pm_opp_get_power(self.as_raw()) })
}
/// Returns the required pstate of an [`OPP`].
#[inline]
pub fn required_pstate(&self, index: u32) -> u32 {
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
unsafe { bindings::dev_pm_opp_get_required_pstate(self.as_raw(), index) }
}
/// Returns true if the [`OPP`] is turbo.
#[inline]
pub fn is_turbo(&self) -> bool {
// SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
// use it.
unsafe { bindings::dev_pm_opp_is_turbo(self.as_raw()) }
}
}