[PATCH V8 07/14] rust: Add initial bindings for OPP framework

Viresh Kumar
2025-02-06T09:29:21Z

This commit adds initial Rust bindings for the Operating performance
points (OPP) core. This adds bindings for struct dev_pm_opp and
struct dev_pm_opp_data to begin with.

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
MAINTAINERS | 1 +
rust/bindings/bindings_helper.h | 1 +
rust/kernel/lib.rs | 2 +
rust/kernel/opp.rs | 189 ++++++++++++++++++++++++++++++++
4 files changed, 193 insertions(+)
create mode 100644 rust/kernel/opp.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 604717065476..cda0d2b74e29 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17732,6 +17732,7 @@ 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>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 4eadcf645df0..7f851d5907af 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -28,6 +28,7 @@
#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>
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 77d3b1f82154..8956f78a2805 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -64,6 +64,8 @@
#[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;
diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
new file mode 100644
index 000000000000..becb33880c92
--- /dev/null
+++ b/rust/kernel/opp.rs
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Operating performance points.
+//!
+//! This module provides bindings for interacting with the OPP subsystem.
+//!
+//! C header: [`include/linux/pm_opp.h`](srctree/include/linux/pm_opp.h)
+
+use crate::{
+ bindings,
+ device::Device,
+ error::{code::*, to_result, Result},
+ types::{ARef, AlwaysRefCounted, Opaque},
+};
+
+use core::ptr;
+
+/// Dynamically created Operating performance point (OPP).
+pub struct Token {
+ dev: ARef<Device>,
+ freq: usize,
+}
+
+impl Token {
+ /// Adds an OPP dynamically.
+ pub 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) };
+ }
+}
+
+/// Equivalent to `struct dev_pm_opp_data` in the C Code.
+#[repr(transparent)]
+pub struct Data(bindings::dev_pm_opp_data);
+
+impl Data {
+ /// Creates new instance of [`Data`].
+ pub fn new(freq: usize, u_volt: usize, level: u32, turbo: bool) -> Self {
+ Self(bindings::dev_pm_opp_data {
+ turbo,
+ freq,
+ u_volt,
+ level,
+ })
+ }
+
+ /// Adds an OPP dynamically. The OPP is freed once the [`Token`] gets freed.
+ pub fn add_opp(self, dev: &ARef<Device>) -> Result<Token> {
+ Token::new(dev, self)
+ }
+
+ fn freq(&self) -> usize {
+ self.0.freq
+ }
+}
+
+/// Operating performance point (OPP).
+///
+/// Wraps the kernel's `struct dev_pm_opp`.
+///
+/// The pointer to `struct dev_pm_opp` is non-null and valid for the lifetime of the `OPP`
+/// instance.
+///
+/// # Invariants
+///
+/// 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's OK to send the ownership of `OPP` across thread boundaries.
+unsafe impl Send for OPP {}
+
+// SAFETY: It's OK 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 OPP's refcount 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.
+ 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.
+ 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>) -> usize {
+ 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.
+ unsafe { bindings::dev_pm_opp_get_freq_indexed(self.as_raw(), index) }
+ }
+
+ /// Returns the voltage of an OPP.
+ pub fn voltage(&self) -> usize {
+ // 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_voltage(self.as_raw()) }
+ }
+
+ /// Returns the level of an OPP.
+ 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.
+ pub fn power(&self) -> usize {
+ // 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_power(self.as_raw()) }
+ }
+
+ /// Returns the required pstate of an OPP.
+ 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.
+ 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()) }
+ }
+}
--
2.31.1.272.g89b43f80a514