[PATCH V10 09/15] rust: opp: Add abstractions for the OPP table

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

Introduce Rust abstractions for `struct opp_table`, enabling access to
OPP tables from Rust.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 rust/kernel/opp.rs | 485 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 484 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
index ec4f67c8aab4..389bcd5e5711 100644
--- a/rust/kernel/opp.rs
+++ b/rust/kernel/opp.rs
@@ -10,8 +10,9 @@
 
 use crate::{
     clk::Hertz,
+    cpumask::{Cpumask, CpumaskVar},
     device::Device,
-    error::{code::*, to_result, Result},
+    error::{code::*, from_err_ptr, to_result, Error, Result},
     ffi::c_ulong,
     types::{ARef, AlwaysRefCounted, Opaque},
 };
@@ -171,6 +172,467 @@ fn freq(&self) -> Hertz {
     }
 }
 
+/// [`OPP`] search options.
+///
+/// ## Examples
+///
+/// Defines how to search for an [`OPP`] in a [`Table`] relative to a frequency.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::error::Result;
+/// use kernel::opp::{OPP, SearchType, Table};
+/// use kernel::types::ARef;
+///
+/// fn find_opp(table: &Table, freq: Hertz) -> Result<ARef<OPP>> {
+///     let opp = table.opp_from_freq(freq, Some(true), None, SearchType::Exact)?;
+///
+///     pr_info!("OPP frequency is: {:?}\n", opp.freq(None));
+///     pr_info!("OPP voltage is: {:?}\n", opp.voltage());
+///     pr_info!("OPP level is: {}\n", opp.level());
+///     pr_info!("OPP power is: {:?}\n", opp.power());
+///
+///     Ok(opp)
+/// }
+/// ```
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum SearchType {
+    /// Match the exact frequency.
+    Exact,
+    /// Find the highest frequency less than or equal to the given value.
+    Floor,
+    /// Find the lowest frequency greater than or equal to the given value.
+    Ceil,
+}
+
+/// A reference-counted OPP table.
+///
+/// Rust abstraction for the C `struct opp_table`.
+///
+/// # Invariants
+///
+/// The pointer stored in `Self` is non-null and valid for the lifetime of the [`Table`].
+///
+/// Instances of this type are reference-counted.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to get OPP [`Table`] for a [`Cpumask`] and set its
+/// frequency.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::cpumask::Cpumask;
+/// use kernel::device::Device;
+/// use kernel::error::Result;
+/// use kernel::opp::Table;
+/// use kernel::types::ARef;
+///
+/// fn get_table(dev: &ARef<Device>, mask: &mut Cpumask, freq: Hertz) -> Result<Table> {
+///     let mut opp_table = Table::from_of_cpumask(dev, mask)?;
+///
+///     if opp_table.opp_count()? == 0 {
+///         return Err(EINVAL);
+///     }
+///
+///     pr_info!("Max transition latency is: {} ns\n", opp_table.max_transition_latency_ns());
+///     pr_info!("Suspend frequency is: {:?}\n", opp_table.suspend_freq());
+///
+///     opp_table.set_rate(freq)?;
+///     Ok(opp_table)
+/// }
+/// ```
+pub struct Table {
+    ptr: *mut bindings::opp_table,
+    dev: ARef<Device>,
+    em: bool,
+    of: bool,
+    cpus: Option<CpumaskVar>,
+}
+
+// SAFETY: It is okay to send ownership of [`Table`] across thread boundaries.
+unsafe impl Send for Table {}
+
+// SAFETY: It is okay to access [`Table`] 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 Table {}
+
+impl Table {
+    /// Creates a new reference-counted [`Table`] from a raw pointer.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `ptr` is valid and non-null.
+    unsafe fn from_raw_table(ptr: *mut bindings::opp_table, dev: &ARef<Device>) -> Self {
+        // SAFETY: By the safety requirements, ptr is valid and its refcount will be incremented.
+        //
+        // INVARIANT: The reference-count is decremented when [`Table`] goes out of scope.
+        unsafe { bindings::dev_pm_opp_get_opp_table_ref(ptr) };
+
+        Self {
+            ptr,
+            dev: dev.clone(),
+            em: false,
+            of: false,
+            cpus: None,
+        }
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Device`].
+    pub fn from_dev(dev: &Device) -> Result<Self> {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        let ptr = from_err_ptr(unsafe { bindings::dev_pm_opp_get_opp_table(dev.as_raw()) })?;
+
+        Ok(Self {
+            ptr,
+            dev: dev.into(),
+            em: false,
+            of: false,
+            cpus: None,
+        })
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Device`] based on device tree
+    /// entries.
+    #[cfg(CONFIG_OF)]
+    pub fn from_of(dev: &ARef<Device>, index: i32) -> Result<Self> {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        to_result(unsafe { bindings::dev_pm_opp_of_add_table_indexed(dev.as_raw(), index) })?;
+
+        // Get the newly created [`Table`].
+        let mut table = Self::from_dev(dev)?;
+        table.of = true;
+
+        Ok(table)
+    }
+
+    // Remove device tree based [`Table`].
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    fn remove_of(&self) {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements. We took the reference from [`from_of`] earlier, it is safe to drop the
+        // same now.
+        unsafe { bindings::dev_pm_opp_of_remove_table(self.dev.as_raw()) };
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Cpumask`] based on device tree
+    /// entries.
+    #[cfg(CONFIG_OF)]
+    pub fn from_of_cpumask(dev: &Device, cpumask: &mut Cpumask) -> Result<Self> {
+        // SAFETY: The cpumask is valid and the returned pointer will be owned by the [`Table`]
+        // instance.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        to_result(unsafe { bindings::dev_pm_opp_of_cpumask_add_table(cpumask.as_raw()) })?;
+
+        // Fetch the newly created table.
+        let mut table = Self::from_dev(dev)?;
+        table.cpus = Some(CpumaskVar::try_clone(cpumask)?);
+
+        Ok(table)
+    }
+
+    // Remove device tree based [`Table`] for a [`Cpumask`].
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    fn remove_of_cpumask(&self, cpumask: &Cpumask) {
+        // SAFETY: The cpumask is valid and we took the reference from [`from_of_cpumask`] earlier,
+        // it is safe to drop the same now.
+        unsafe { bindings::dev_pm_opp_of_cpumask_remove_table(cpumask.as_raw()) };
+    }
+
+    /// Returns the number of [`OPP`]s in the [`Table`].
+    pub fn opp_count(&self) -> Result<u32> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        let ret = unsafe { bindings::dev_pm_opp_get_opp_count(self.dev.as_raw()) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u32)
+        }
+    }
+
+    /// Returns max clock latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_clock_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_clock_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns max volt latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_volt_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_volt_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns max transition latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_transition_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_transition_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns the suspend [`OPP`]'s frequency.
+    #[inline]
+    pub fn suspend_freq(&self) -> Hertz {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        Hertz(unsafe { bindings::dev_pm_opp_get_suspend_opp_freq(self.dev.as_raw()) })
+    }
+
+    /// Synchronizes regulators used by the [`Table`].
+    #[inline]
+    pub fn sync_regulators(&self) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_sync_regulators(self.dev.as_raw()) })
+    }
+
+    /// Gets sharing CPUs.
+    #[inline]
+    pub fn sharing_cpus(dev: &Device, cpumask: &mut Cpumask) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_get_sharing_cpus(dev.as_raw(), cpumask.as_raw()) })
+    }
+
+    /// Sets sharing CPUs.
+    pub fn set_sharing_cpus(&mut self, cpumask: &mut Cpumask) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_set_sharing_cpus(self.dev.as_raw(), cpumask.as_raw())
+        })?;
+
+        if let Some(mask) = self.cpus.as_mut() {
+            // Update the cpumask as this will be used while removing the table.
+            cpumask.copy(mask);
+        }
+
+        Ok(())
+    }
+
+    /// Gets sharing CPUs from device tree.
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    pub fn of_sharing_cpus(dev: &Device, cpumask: &mut Cpumask) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_of_get_sharing_cpus(dev.as_raw(), cpumask.as_raw())
+        })
+    }
+
+    /// Updates the voltage value for an [`OPP`].
+    #[inline]
+    pub fn adjust_voltage(
+        &self,
+        freq: Hertz,
+        volt: MicroVolt,
+        volt_min: MicroVolt,
+        volt_max: MicroVolt,
+    ) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_adjust_voltage(
+                self.dev.as_raw(),
+                freq.into(),
+                volt.into(),
+                volt_min.into(),
+                volt_max.into(),
+            )
+        })
+    }
+
+    /// Configures device with [`OPP`] matching the frequency value.
+    #[inline]
+    pub fn set_rate(&self, freq: Hertz) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_set_rate(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Configures device with [`OPP`].
+    #[inline]
+    pub fn set_opp(&self, opp: &OPP) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_set_opp(self.dev.as_raw(), opp.as_raw()) })
+    }
+
+    /// Finds [`OPP`] based on frequency.
+    pub fn opp_from_freq(
+        &self,
+        freq: Hertz,
+        available: Option<bool>,
+        index: Option<u32>,
+        stype: SearchType,
+    ) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+        let index = index.unwrap_or(0);
+        let mut rate = freq.into();
+
+        let ptr = from_err_ptr(match stype {
+            SearchType::Exact => {
+                if let Some(available) = available {
+                    // SAFETY: The requirements are satisfied by the existence of [`Device`] and
+                    // its safety requirements. The returned pointer will be owned by the new
+                    // [`OPP`] instance.
+                    unsafe {
+                        bindings::dev_pm_opp_find_freq_exact_indexed(
+                            raw_dev, rate, index, available,
+                        )
+                    }
+                } else {
+                    return Err(EINVAL);
+                }
+            }
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_freq_ceil_indexed(raw_dev, &mut rate, index)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_freq_floor_indexed(raw_dev, &mut rate, index)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Finds [`OPP`] based on level.
+    pub fn opp_from_level(&self, mut level: u32, stype: SearchType) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+
+        let ptr = from_err_ptr(match stype {
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Exact => unsafe { bindings::dev_pm_opp_find_level_exact(raw_dev, level) },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_level_ceil(raw_dev, &mut level)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_level_floor(raw_dev, &mut level)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Finds [`OPP`] based on bandwidth.
+    pub fn opp_from_bw(&self, mut bw: u32, index: i32, stype: SearchType) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+
+        let ptr = from_err_ptr(match stype {
+            // The OPP core doesn't support this yet.
+            SearchType::Exact => return Err(EINVAL),
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_bw_ceil(raw_dev, &mut bw, index)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_bw_floor(raw_dev, &mut bw, index)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Enables the [`OPP`].
+    #[inline]
+    pub fn enable_opp(&self, freq: Hertz) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_enable(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Disables the [`OPP`].
+    #[inline]
+    pub fn disable_opp(&self, freq: Hertz) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_disable(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Registers with Energy model.
+    #[cfg(CONFIG_OF)]
+    pub fn of_register_em(&mut self, cpumask: &mut Cpumask) -> Result<()> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_of_register_em(self.dev.as_raw(), cpumask.as_raw())
+        })?;
+
+        self.em = true;
+        Ok(())
+    }
+
+    // Unregisters with Energy model.
+    #[cfg(all(CONFIG_OF, CONFIG_ENERGY_MODEL))]
+    #[inline]
+    fn of_unregister_em(&self) {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements. We registered with the EM framework earlier, it is safe to unregister now.
+        unsafe { bindings::em_dev_unregister_perf_domain(self.dev.as_raw()) };
+    }
+}
+
+impl Drop for Table {
+    fn drop(&mut self) {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe
+        // to relinquish it now.
+        unsafe { bindings::dev_pm_opp_put_opp_table(self.ptr) };
+
+        #[cfg(CONFIG_OF)]
+        {
+            #[cfg(CONFIG_ENERGY_MODEL)]
+            if self.em {
+                self.of_unregister_em();
+            }
+
+            if self.of {
+                self.remove_of();
+            } else if let Some(cpumask) = self.cpus.take() {
+                self.remove_of_cpumask(&cpumask);
+            }
+        }
+    }
+}
+
 /// A reference-counted Operating performance point (OPP).
 ///
 /// Rust abstraction for the C `struct dev_pm_opp`.
@@ -184,6 +646,27 @@ fn freq(&self) -> Hertz {
 /// represents a pointer that owns a reference count on the [`OPP`].
 ///
 /// A reference to the [`OPP`], &[`OPP`], isn't refcounted by the Rust code.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to get [`OPP`] corresponding to a frequency value and
+/// configure the device with it.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::error::Result;
+/// use kernel::opp::{SearchType, Table};
+///
+/// fn configure_opp(table: &Table, freq: Hertz) -> Result {
+///     let opp = table.opp_from_freq(freq, Some(true), None, SearchType::Exact)?;
+///
+///     if opp.freq(None) != freq {
+///         return Err(EINVAL);
+///     }
+///
+///     table.set_opp(&opp)
+/// }
+/// ```
 #[repr(transparent)]
 pub struct OPP(Opaque<bindings::dev_pm_opp>);
 
-- 
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