kernel/

clk.rs

// SPDX-License-Identifier: GPL-2.0

//! Clock abstractions.
//!
//! C header: [`include/linux/clk.h`](srctree/include/linux/clk.h)
//!
//! Reference: <https://docs.kernel.org/driver-api/clk.html>

use crate::{
    device::Device,
    error::{from_err_ptr, to_result, Result},
    ffi::c_ulong,
    prelude::*,
};

use core::{ops::Deref, ptr};

/// The frequency unit.
///
/// Represents a frequency in hertz, wrapping a [`c_ulong`] value.
///
/// ## Examples
///
/// ```
/// use kernel::clk::Hertz;
///
/// let hz = 1_000_000_000;
/// let rate = Hertz(hz);
///
/// assert_eq!(rate.as_hz(), hz);
/// assert_eq!(rate, Hertz(hz));
/// assert_eq!(rate, Hertz::from_khz(hz / 1_000));
/// assert_eq!(rate, Hertz::from_mhz(hz / 1_000_000));
/// assert_eq!(rate, Hertz::from_ghz(hz / 1_000_000_000));
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct Hertz(pub c_ulong);

impl Hertz {
    /// Create a new instance from kilohertz (kHz)
    pub fn from_khz(khz: c_ulong) -> Self {
        Self(khz * 1_000)
    }

    /// Create a new instance from megahertz (MHz)
    pub fn from_mhz(mhz: c_ulong) -> Self {
        Self(mhz * 1_000_000)
    }

    /// Create a new instance from gigahertz (GHz)
    pub fn from_ghz(ghz: c_ulong) -> Self {
        Self(ghz * 1_000_000_000)
    }

    /// Get the frequency in hertz
    pub fn as_hz(&self) -> c_ulong {
        self.0
    }

    /// Get the frequency in kilohertz
    pub fn as_khz(&self) -> c_ulong {
        self.0 / 1_000
    }

    /// Get the frequency in megahertz
    pub fn as_mhz(&self) -> c_ulong {
        self.0 / 1_000_000
    }

    /// Get the frequency in gigahertz
    pub fn as_ghz(&self) -> c_ulong {
        self.0 / 1_000_000_000
    }
}

impl From<Hertz> for c_ulong {
    fn from(freq: Hertz) -> Self {
        freq.0
    }
}

/// A reference-counted clock.
///
/// Rust abstraction for the C [`struct clk`].
///
/// # Invariants
///
/// A [`Clk`] instance holds either a pointer to a valid [`struct clk`] created by the C portion of
/// the kernel or a NULL pointer.
///
/// Instances of this type are reference-counted. Calling [`Clk::get`] ensures that the allocation
/// remains valid for the lifetime of the [`Clk`].
///
/// ## Examples
///
/// The following example demonstrates how to obtain and configure a clock for a device.
///
/// ```
/// use kernel::c_str;
/// use kernel::clk::{Clk, Hertz};
/// use kernel::device::Device;
/// use kernel::error::Result;
///
/// fn configure_clk(dev: &Device) -> Result {
///     let clk = Clk::get(dev, Some(c_str!("apb_clk")))?;
///
///     clk.prepare_enable()?;
///
///     let expected_rate = Hertz::from_ghz(1);
///
///     if clk.rate() != expected_rate {
///         clk.set_rate(expected_rate)?;
///     }
///
///     clk.disable_unprepare();
///     Ok(())
/// }
/// ```
///
/// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html
#[repr(transparent)]
pub struct Clk(*mut bindings::clk);

impl Clk {
    /// Gets [`Clk`] corresponding to a [`Device`] and a connection id.
    ///
    /// Equivalent to the kernel's [`clk_get`] API.
    ///
    /// [`clk_get`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_get
    pub fn get(dev: &Device, name: Option<&CStr>) -> Result<Self> {
        let con_id = if let Some(name) = name {
            name.as_ptr()
        } else {
            ptr::null()
        };

        // SAFETY: It is safe to call [`clk_get`] for a valid device pointer.
        //
        // INVARIANT: The reference-count is decremented when [`Clk`] goes out of scope.
        Ok(Self(from_err_ptr(unsafe {
            bindings::clk_get(dev.as_raw(), con_id)
        })?))
    }

    /// Obtain the raw [`struct clk`] pointer.
    #[inline]
    pub fn as_raw(&self) -> *mut bindings::clk {
        self.0
    }

    /// Enable the clock.
    ///
    /// Equivalent to the kernel's [`clk_enable`] API.
    ///
    /// [`clk_enable`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_enable
    #[inline]
    pub fn enable(&self) -> Result {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_enable`].
        to_result(unsafe { bindings::clk_enable(self.as_raw()) })
    }

    /// Disable the clock.
    ///
    /// Equivalent to the kernel's [`clk_disable`] API.
    ///
    /// [`clk_disable`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_disable
    #[inline]
    pub fn disable(&self) {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_disable`].
        unsafe { bindings::clk_disable(self.as_raw()) };
    }

    /// Prepare the clock.
    ///
    /// Equivalent to the kernel's [`clk_prepare`] API.
    ///
    /// [`clk_prepare`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_prepare
    #[inline]
    pub fn prepare(&self) -> Result {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_prepare`].
        to_result(unsafe { bindings::clk_prepare(self.as_raw()) })
    }

    /// Unprepare the clock.
    ///
    /// Equivalent to the kernel's [`clk_unprepare`] API.
    ///
    /// [`clk_unprepare`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_unprepare
    #[inline]
    pub fn unprepare(&self) {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_unprepare`].
        unsafe { bindings::clk_unprepare(self.as_raw()) };
    }

    /// Prepare and enable the clock.
    ///
    /// Equivalent to calling [`Clk::prepare`] followed by [`Clk::enable`].
    #[inline]
    pub fn prepare_enable(&self) -> Result {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for
        // [`clk_prepare_enable`].
        to_result(unsafe { bindings::clk_prepare_enable(self.as_raw()) })
    }

    /// Disable and unprepare the clock.
    ///
    /// Equivalent to calling [`Clk::disable`] followed by [`Clk::unprepare`].
    #[inline]
    pub fn disable_unprepare(&self) {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for
        // [`clk_disable_unprepare`].
        unsafe { bindings::clk_disable_unprepare(self.as_raw()) };
    }

    /// Get clock's rate.
    ///
    /// Equivalent to the kernel's [`clk_get_rate`] API.
    ///
    /// [`clk_get_rate`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_get_rate
    #[inline]
    pub fn rate(&self) -> Hertz {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_get_rate`].
        Hertz(unsafe { bindings::clk_get_rate(self.as_raw()) })
    }

    /// Set clock's rate.
    ///
    /// Equivalent to the kernel's [`clk_set_rate`] API.
    ///
    /// [`clk_set_rate`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_set_rate
    #[inline]
    pub fn set_rate(&self, rate: Hertz) -> Result {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_set_rate`].
        to_result(unsafe { bindings::clk_set_rate(self.as_raw(), rate.as_hz()) })
    }
}

impl Drop for Clk {
    fn drop(&mut self) {
        // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_put`].
        unsafe { bindings::clk_put(self.as_raw()) };
    }
}

/// A reference-counted optional clock.
///
/// A lightweight wrapper around an optional [`Clk`]. An [`OptionalClk`] represents a [`Clk`] that
/// a driver can function without but may improve performance or enable additional features when
/// available.
///
/// # Invariants
///
/// An [`OptionalClk`] instance encapsulates a [`Clk`] with either a valid [`struct clk`] or `NULL`
/// pointer.
///
/// Instances of this type are reference-counted. Calling [`OptionalClk::get`] ensures that the
/// allocation remains valid for the lifetime of the [`OptionalClk`].
///
/// ## Examples
///
/// The following example demonstrates how to obtain and configure an optional clock for a device.
/// The code functions correctly whether or not the clock is available.
///
/// ```
/// use kernel::c_str;
/// use kernel::clk::{OptionalClk, Hertz};
/// use kernel::device::Device;
/// use kernel::error::Result;
///
/// fn configure_clk(dev: &Device) -> Result {
///     let clk = OptionalClk::get(dev, Some(c_str!("apb_clk")))?;
///
///     clk.prepare_enable()?;
///
///     let expected_rate = Hertz::from_ghz(1);
///
///     if clk.rate() != expected_rate {
///         clk.set_rate(expected_rate)?;
///     }
///
///     clk.disable_unprepare();
///     Ok(())
/// }
/// ```
///
/// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html
pub struct OptionalClk(Clk);

impl OptionalClk {
    /// Gets [`OptionalClk`] corresponding to a [`Device`] and a connection id.
    ///
    /// Equivalent to the kernel's [`clk_get_optional`] API.
    ///
    /// [`clk_get_optional`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_get_optional
    pub fn get(dev: &Device, name: Option<&CStr>) -> Result<Self> {
        let con_id = if let Some(name) = name {
            name.as_ptr()
        } else {
            ptr::null()
        };

        // SAFETY: It is safe to call [`clk_get_optional`] for a valid device pointer.
        //
        // INVARIANT: The reference-count is decremented when [`OptionalClk`] goes out of scope.
        Ok(Self(Clk(from_err_ptr(unsafe {
            bindings::clk_get_optional(dev.as_raw(), con_id)
        })?)))
    }
}

// Make [`OptionalClk`] behave like [`Clk`].
impl Deref for OptionalClk {
    type Target = Clk;

    fn deref(&self) -> &Clk {
        &self.0
    }
}