[PATCH V12 12/15] rust: cpufreq: Extend abstractions for policy and driver ops

[Viresh Kumar <viresh.kumar@linaro.org>]

Extend the cpufreq abstractions to include support for policy handling
and driver operations.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 rust/kernel/cpufreq.rs | 463 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 461 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index 2aa024615d4d..4e6d85bd06f4 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -10,13 +10,25 @@
 
 use crate::{
     clk::Hertz,
-    error::{code::*, to_result, Result},
+    cpumask,
+    device::Device,
+    error::{code::*, from_err_ptr, to_result, Result, VTABLE_DEFAULT_ERROR},
     ffi::c_ulong,
     prelude::*,
+    types::ForeignOwnable,
     types::Opaque,
 };
 
-use core::{ops::Deref, pin::Pin};
+#[cfg(CONFIG_COMMON_CLK)]
+use crate::clk::Clk;
+
+use core::{
+    ops::{Deref, DerefMut},
+    pin::Pin,
+    ptr,
+};
+
+use macros::vtable;
 
 /// Default transition latency value in nanoseconds.
 pub const ETERNAL_LATENCY_NS: u32 = bindings::CPUFREQ_ETERNAL as u32;
@@ -362,3 +374,450 @@ pub fn to_table(mut self) -> Result<TableBox> {
         TableBox::new(self.entries)
     }
 }
+
+/// CPU frequency policy.
+///
+/// Rust abstraction for the C `struct cpufreq_policy`.
+///
+/// # Invariants
+///
+/// A [`Policy`] instance always corresponds to a valid C `struct cpufreq_policy`.
+///
+/// The callers must ensure that the `struct cpufreq_policy` is valid for access and remains valid
+/// for the lifetime of the returned reference.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create a CPU frequency table.
+///
+/// ```
+/// use kernel::cpufreq::{ETERNAL_LATENCY_NS, Policy};
+///
+/// fn update_policy(policy: &mut Policy) {
+///     policy
+///         .set_dvfs_possible_from_any_cpu(true)
+///         .set_fast_switch_possible(true)
+///         .set_transition_latency_ns(ETERNAL_LATENCY_NS);
+///
+///     pr_info!("The policy details are: {:?}\n", (policy.cpu(), policy.cur()));
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Policy(Opaque<bindings::cpufreq_policy>);
+
+impl Policy {
+    /// Creates a reference to an existing `struct cpufreq_policy` 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_policy) -> &'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() }
+    }
+
+    /// Creates a mutable reference to an existing `struct cpufreq_policy` 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) -> &'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 mutable pointer to the C `struct cpufreq_policy`.
+    #[inline]
+    fn as_raw(&self) -> *mut bindings::cpufreq_policy {
+        let this: *const Self = self;
+        this.cast_mut().cast()
+    }
+
+    #[inline]
+    fn as_ref(&self) -> &bindings::cpufreq_policy {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { &*self.as_raw() }
+    }
+
+    #[inline]
+    fn as_mut_ref(&mut self) -> &mut bindings::cpufreq_policy {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { &mut *self.as_raw() }
+    }
+
+    /// Returns the primary CPU for the [`Policy`].
+    #[inline]
+    pub fn cpu(&self) -> u32 {
+        self.as_ref().cpu
+    }
+
+    /// Returns the minimum frequency for the [`Policy`].
+    #[inline]
+    pub fn min(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().min as usize)
+    }
+
+    /// Set the minimum frequency for the [`Policy`].
+    #[inline]
+    pub fn set_min(&mut self, min: Hertz) -> &mut Self {
+        self.as_mut_ref().min = min.as_khz() as u32;
+        self
+    }
+
+    /// Returns the maximum frequency for the [`Policy`].
+    #[inline]
+    pub fn max(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().max as usize)
+    }
+
+    /// Set the maximum frequency for the [`Policy`].
+    #[inline]
+    pub fn set_max(&mut self, max: Hertz) -> &mut Self {
+        self.as_mut_ref().max = max.as_khz() as u32;
+        self
+    }
+
+    /// Returns the current frequency for the [`Policy`].
+    #[inline]
+    pub fn cur(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().cur as usize)
+    }
+
+    /// Returns the suspend frequency for the [`Policy`].
+    #[inline]
+    pub fn suspend_freq(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().suspend_freq as usize)
+    }
+
+    /// Sets the suspend frequency for the [`Policy`].
+    #[inline]
+    pub fn set_suspend_freq(&mut self, freq: Hertz) -> &mut Self {
+        self.as_mut_ref().suspend_freq = freq.as_khz() as u32;
+        self
+    }
+
+    /// Provides a wrapper to the generic suspend routine.
+    #[inline]
+    pub fn generic_suspend(&mut self) -> Result<()> {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        to_result(unsafe { bindings::cpufreq_generic_suspend(self.as_mut_ref()) })
+    }
+
+    /// Provides a wrapper to the generic get routine.
+    #[inline]
+    pub fn generic_get(&self) -> Result<u32> {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        Ok(unsafe { bindings::cpufreq_generic_get(self.cpu()) })
+    }
+
+    /// Provides a wrapper to the register with energy model using the OPP core.
+    #[cfg(CONFIG_PM_OPP)]
+    #[inline]
+    pub fn register_em_opp(&mut self) {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { bindings::cpufreq_register_em_with_opp(self.as_mut_ref()) };
+    }
+
+    /// Gets [`cpumask::Cpumask`] for a cpufreq [`Policy`].
+    #[inline]
+    pub fn cpus(&mut self) -> &mut cpumask::Cpumask {
+        // SAFETY: The pointer to `cpus` is valid for writing and remains valid for the lifetime of
+        // the returned reference.
+        unsafe { cpumask::CpumaskVar::as_mut_ref(&mut self.as_mut_ref().cpus) }
+    }
+
+    /// Sets clock for the [`Policy`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must guarantee that the returned [`Clk`] is not dropped while it is getting used
+    /// by the C code.
+    #[cfg(CONFIG_COMMON_CLK)]
+    pub unsafe fn set_clk(&mut self, dev: &Device, name: Option<&CStr>) -> Result<Clk> {
+        let clk = Clk::get(dev, name)?;
+        self.as_mut_ref().clk = clk.as_raw();
+        Ok(clk)
+    }
+
+    /// Allows / disallows frequency switching code to run on any CPU.
+    #[inline]
+    pub fn set_dvfs_possible_from_any_cpu(&mut self, val: bool) -> &mut Self {
+        self.as_mut_ref().dvfs_possible_from_any_cpu = val;
+        self
+    }
+
+    /// Returns if fast switching of frequencies is possible or not.
+    #[inline]
+    pub fn fast_switch_possible(&self) -> bool {
+        self.as_ref().fast_switch_possible
+    }
+
+    /// Enables / disables fast frequency switching.
+    #[inline]
+    pub fn set_fast_switch_possible(&mut self, val: bool) -> &mut Self {
+        self.as_mut_ref().fast_switch_possible = val;
+        self
+    }
+
+    /// Sets transition latency (in nanoseconds) for the [`Policy`].
+    #[inline]
+    pub fn set_transition_latency_ns(&mut self, latency_ns: u32) -> &mut Self {
+        self.as_mut_ref().cpuinfo.transition_latency = latency_ns;
+        self
+    }
+
+    /// Sets cpuinfo `min_freq`.
+    #[inline]
+    pub fn set_cpuinfo_min_freq(&mut self, min_freq: Hertz) -> &mut Self {
+        self.as_mut_ref().cpuinfo.min_freq = min_freq.as_khz() as u32;
+        self
+    }
+
+    /// Sets cpuinfo `max_freq`.
+    #[inline]
+    pub fn set_cpuinfo_max_freq(&mut self, max_freq: Hertz) -> &mut Self {
+        self.as_mut_ref().cpuinfo.max_freq = max_freq.as_khz() as u32;
+        self
+    }
+
+    /// Set `transition_delay_us`, i.e. the minimum time between successive frequency change
+    /// requests.
+    #[inline]
+    pub fn set_transition_delay_us(&mut self, transition_delay_us: u32) -> &mut Self {
+        self.as_mut_ref().transition_delay_us = transition_delay_us;
+        self
+    }
+
+    /// Returns reference to the CPU frequency [`Table`] for the [`Policy`].
+    pub fn freq_table(&self) -> Result<&Table> {
+        if self.as_ref().freq_table.is_null() {
+            return Err(EINVAL);
+        }
+
+        // SAFETY: The `freq_table` is guaranteed to be valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        Ok(unsafe { Table::from_raw(self.as_ref().freq_table) })
+    }
+
+    /// Sets the CPU frequency [`Table`] for the [`Policy`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must guarantee that the [`Table`] is not dropped while it is getting used by the
+    /// C code.
+    #[inline]
+    pub unsafe fn set_freq_table(&mut self, table: &Table) -> &mut Self {
+        self.as_mut_ref().freq_table = table.as_raw();
+        self
+    }
+
+    /// Returns the [`Policy`]'s private data.
+    pub fn data<T: ForeignOwnable>(&mut self) -> Option<<T>::Borrowed<'_>> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            // SAFETY: The data is earlier set from [`set_data`].
+            Some(unsafe { T::borrow(self.as_ref().driver_data) })
+        }
+    }
+
+    /// Sets the private data of the [`Policy`] using a foreign-ownable wrapper.
+    ///
+    /// # Errors
+    ///
+    /// Returns `EBUSY` if private data is already set.
+    fn set_data<T: ForeignOwnable>(&mut self, data: T) -> Result<()> {
+        if self.as_ref().driver_data.is_null() {
+            // Transfer the ownership of the data to the foreign interface.
+            self.as_mut_ref().driver_data = <T as ForeignOwnable>::into_foreign(data) as _;
+            Ok(())
+        } else {
+            Err(EBUSY)
+        }
+    }
+
+    /// Clears and returns ownership of the private data.
+    fn clear_data<T: ForeignOwnable>(&mut self) -> Option<T> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            let data = Some(
+                // SAFETY: The data is earlier set by us from [`set_data`]. It is safe to take
+                // back the ownership of the data from the foreign interface.
+                unsafe { <T as ForeignOwnable>::from_foreign(self.as_ref().driver_data) },
+            );
+            self.as_mut_ref().driver_data = ptr::null_mut();
+            data
+        }
+    }
+}
+
+/// CPU frequency policy created from a CPU number.
+///
+/// This struct represents the CPU frequency policy obtained for a specific CPU, providing safe
+/// access to the underlying `cpufreq_policy` and ensuring proper cleanup when the `PolicyCpu` is
+/// dropped.
+struct PolicyCpu<'a>(&'a mut Policy);
+
+impl<'a> PolicyCpu<'a> {
+    fn from_cpu(cpu: u32) -> Result<Self> {
+        // SAFETY: It is safe to call `cpufreq_cpu_get` for any valid CPU.
+        let ptr = from_err_ptr(unsafe { bindings::cpufreq_cpu_get(cpu) })?;
+
+        Ok(Self(
+            // SAFETY: The `ptr` is guaranteed to be valid and remains valid for the lifetime of
+            // the returned reference.
+            unsafe { Policy::from_raw_mut(ptr) },
+        ))
+    }
+}
+
+impl<'a> Deref for PolicyCpu<'a> {
+    type Target = Policy;
+
+    fn deref(&self) -> &Self::Target {
+        self.0
+    }
+}
+
+impl<'a> DerefMut for PolicyCpu<'a> {
+    fn deref_mut(&mut self) -> &mut Policy {
+        self.0
+    }
+}
+
+impl<'a> Drop for PolicyCpu<'a> {
+    fn drop(&mut self) {
+        // SAFETY: The underlying pointer is guaranteed to be valid for the lifetime of `self`.
+        unsafe { bindings::cpufreq_cpu_put(self.0.as_raw()) };
+    }
+}
+
+/// CPU frequency driver.
+///
+/// Implement this trait to provide a CPU frequency driver and its callbacks.
+///
+/// Reference: <https://docs.kernel.org/cpu-freq/cpu-drivers.html>
+#[vtable]
+pub trait Driver {
+    /// Driver's name.
+    const NAME: &'static CStr;
+
+    /// Driver's flags.
+    const FLAGS: u16;
+
+    /// Boost support.
+    const BOOST_ENABLED: bool;
+
+    /// Policy specific data.
+    ///
+    /// Require that `PData` implements `ForeignOwnable`. We guarantee to never move the underlying
+    /// wrapped data structure.
+    type PData: ForeignOwnable;
+
+    /// Driver's `init` callback.
+    fn init(policy: &mut Policy) -> Result<Self::PData>;
+
+    /// Driver's `exit` callback.
+    fn exit(_policy: &mut Policy, _data: Option<Self::PData>) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `online` callback.
+    fn online(_policy: &mut Policy) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `offline` callback.
+    fn offline(_policy: &mut Policy) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `suspend` callback.
+    fn suspend(_policy: &mut Policy) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `resume` callback.
+    fn resume(_policy: &mut Policy) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `ready` callback.
+    fn ready(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `verify` callback.
+    fn verify(data: &mut PolicyData) -> Result<()>;
+
+    /// Driver's `setpolicy` callback.
+    fn setpolicy(_policy: &mut Policy) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target` callback.
+    fn target(_policy: &mut Policy, _target_freq: u32, _relation: Relation) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target_index` callback.
+    fn target_index(_policy: &mut Policy, _index: TableIndex) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `fast_switch` callback.
+    fn fast_switch(_policy: &mut Policy, _target_freq: u32) -> u32 {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `adjust_perf` callback.
+    fn adjust_perf(_policy: &mut Policy, _min_perf: usize, _target_perf: usize, _capacity: usize) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `get_intermediate` callback.
+    fn get_intermediate(_policy: &mut Policy, _index: TableIndex) -> u32 {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target_intermediate` callback.
+    fn target_intermediate(_policy: &mut Policy, _index: TableIndex) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `get` callback.
+    fn get(_policy: &mut Policy) -> Result<u32> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `update_limits` callback.
+    fn update_limits(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `bios_limit` callback.
+    fn bios_limit(_policy: &mut Policy, _limit: &mut u32) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `set_boost` callback.
+    fn set_boost(_policy: &mut Policy, _state: i32) -> Result<()> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `register_em` callback.
+    fn register_em(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+}
-- 
2.31.1.272.g89b43f80a514