[PATCH V4 0/2] rust: Add basic clock abstractions

[PATCH V4 0/2] rust: Add basic clock abstractions

[Viresh Kumar]

Hello,

This adds initial abstractions for the clk APIs. These provide the minimal
functionality needed for common use cases, making them straightforward to
introduce in the first iteration.

These will be used by Rust based cpufreq / OPP layers to begin with.

For now I have added them under the maintainership umbrella of the common clk
framework, please let me know if I should do it differently.

If possible, I would like to get these merged via the PM tree along with
cpufreq/OPP abstractions, but its okay otherwise too.

Miguel: I have dropped the changes related to a Guard implementation for clk
APIs as the discussion wasn't conclusive enough. Maybe we can tackle that later
if required.

--
Viresh

V3->V4:
- Enable clk abstractions only for cfg(CONFIG_COMMON_CLK) (Stephen Boyd).
- New struct implementation of Hertz.
- Added examples for all the structures.
- Make methods inline.
- Improved comments, Invariants, INVARIANT, SAFETY sections / comments, use
  intra-doc links.
- Other minor improvements.

V2->V3:
- Add type Hertz (Daniel Almeida).
- Improved comments in helpers.rs (Daniel Almeida).
- s/Clk::new/Clk::get/ (Daniel Almeida).
- Implement OptionalClk as well (Rob Herring).
- Fix Safety comments (Danilo Krummrich).
- Add tags from Daniel Almeida.

V1->V2:
- Post this as an independent series.
- Include more APIs, apart from clk_get() and clk_put().

Viresh Kumar (2):
  rust: Add clk helpers
  rust: Add initial clk abstractions

 MAINTAINERS                     |   2 +
 rust/bindings/bindings_helper.h |   1 +
 rust/helpers/clk.c              |  66 +++++++
 rust/helpers/helpers.c          |   1 +
 rust/kernel/clk.rs              | 304 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 6 files changed, 376 insertions(+)
 create mode 100644 rust/helpers/clk.c
 create mode 100644 rust/kernel/clk.rs

-- 
2.31.1.272.g89b43f80a514

[PATCH V4 1/2] rust: Add clk helpers

[Viresh Kumar]

Non-trivial C macros and inlined C functions cannot be used directly
in the Rust code and are used via functions ("helpers") that wrap
those so that they can be called from Rust.

In order to prepare for adding Rust abstractions for the clock APIs,
add clock helpers required by the Rust implementation.

Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 MAINTAINERS                     |  1 +
 rust/bindings/bindings_helper.h |  1 +
 rust/helpers/clk.c              | 66 +++++++++++++++++++++++++++++++++
 rust/helpers/helpers.c          |  1 +
 4 files changed, 69 insertions(+)
 create mode 100644 rust/helpers/clk.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 25c86f47353d..726110d3c988 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5778,6 +5778,7 @@ F:	include/dt-bindings/clock/
 F:	include/linux/clk-pr*
 F:	include/linux/clk/
 F:	include/linux/of_clk.h
+F:	rust/helpers/clk.c
 X:	drivers/clk/clkdev.c
 
 COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 55354e4dec14..4e4e16c3b479 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -10,6 +10,7 @@
 #include <linux/blk-mq.h>
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
+#include <linux/clk.h>
 #include <linux/cred.h>
 #include <linux/errname.h>
 #include <linux/ethtool.h>
diff --git a/rust/helpers/clk.c b/rust/helpers/clk.c
new file mode 100644
index 000000000000..6d04372c9f3b
--- /dev/null
+++ b/rust/helpers/clk.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/clk.h>
+
+/*
+ * The "inline" implementation of below helpers are only available when
+ * CONFIG_HAVE_CLK or CONFIG_HAVE_CLK_PREPARE aren't set.
+ */
+#ifndef CONFIG_HAVE_CLK
+struct clk *rust_helper_clk_get(struct device *dev, const char *id)
+{
+	return clk_get(dev, id);
+}
+
+void rust_helper_clk_put(struct clk *clk)
+{
+	clk_put(clk);
+}
+
+int rust_helper_clk_enable(struct clk *clk)
+{
+	return clk_enable(clk);
+}
+
+void rust_helper_clk_disable(struct clk *clk)
+{
+	clk_disable(clk);
+}
+
+unsigned long rust_helper_clk_get_rate(struct clk *clk)
+{
+	return clk_get_rate(clk);
+}
+
+int rust_helper_clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	return clk_set_rate(clk, rate);
+}
+#endif
+
+#ifndef CONFIG_HAVE_CLK_PREPARE
+int rust_helper_clk_prepare(struct clk *clk)
+{
+	return clk_prepare(clk);
+}
+
+void rust_helper_clk_unprepare(struct clk *clk)
+{
+	clk_unprepare(clk);
+}
+#endif
+
+struct clk *rust_helper_clk_get_optional(struct device *dev, const char *id)
+{
+	return clk_get_optional(dev, id);
+}
+
+int rust_helper_clk_prepare_enable(struct clk *clk)
+{
+	return clk_prepare_enable(clk);
+}
+
+void rust_helper_clk_disable_unprepare(struct clk *clk)
+{
+	clk_disable_unprepare(clk);
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 0640b7e115be..4700ee7aaf85 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -11,6 +11,7 @@
 #include "bug.c"
 #include "build_assert.c"
 #include "build_bug.c"
+#include "clk.c"
 #include "cred.c"
 #include "device.c"
 #include "err.c"
-- 
2.31.1.272.g89b43f80a514

[PATCH V4 2/2] rust: Add initial clk abstractions

[Viresh Kumar]

Add initial abstractions for the clk APIs. These provide the minimal
functionality needed for common use cases, making them straightforward
to introduce in the first iteration.

These will be used by Rust based cpufreq / OPP layers to begin with.

Tested-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 MAINTAINERS        |   1 +
 rust/kernel/clk.rs | 304 +++++++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs |   2 +
 3 files changed, 307 insertions(+)
 create mode 100644 rust/kernel/clk.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 726110d3c988..96e2574f41c0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5779,6 +5779,7 @@ F:	include/linux/clk-pr*
 F:	include/linux/clk/
 F:	include/linux/of_clk.h
 F:	rust/helpers/clk.c
+F:	rust/kernel/clk.rs
 X:	drivers/clk/clkdev.c
 
 COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)
diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
new file mode 100644
index 000000000000..52dbd6b5a050
--- /dev/null
+++ b/rust/kernel/clk.rs
@@ -0,0 +1,304 @@
+// 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::{
+    bindings,
+    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
+    }
+}
+
+impl From<Hertz> for c_ulong {
+    fn from(freq: Hertz) -> Self {
+        freq.0
+    }
+}
+
+/// A reference-counted clock.
+///
+/// This represents the 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() as *const _
+        } 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() as *const _
+        } 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
+    }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 496ed32b0911..3748f954d71f 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -40,6 +40,8 @@
 pub mod block;
 #[doc(hidden)]
 pub mod build_assert;
+#[cfg(CONFIG_COMMON_CLK)]
+pub mod clk;
 pub mod cred;
 pub mod device;
 pub mod device_id;
-- 
2.31.1.272.g89b43f80a514