[PATCH 0/2] rust: clk: Add ExclusiveClk and use it in pwm-th1520

[PATCH 0/2] rust: clk: Add ExclusiveClk and use it in pwm-th1520

[Maurice Hieronymus via B4 Relay]

Add a Rust binding for clk_rate_exclusive_get() / clk_rate_exclusive_put()
and use it in pwm-th1520, which previously carried a TODO noting the
missing binding.

Based on pwm/for-next.

Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
---
Maurice Hieronymus (2):
      rust: clk: Add ExclusiveClk wrapper for clk_rate_exclusive_get
      pwm: th1520: Lock clock rate with clk_rate_exclusive_get

 drivers/pwm/pwm_th1520.rs |  8 +++---
 rust/kernel/clk.rs        | 65 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 5 deletions(-)
---
base-commit: 0e5e0db3e954b32a410ab4f74a4faac7a0e8889f
change-id: 20260526-rate-exclusive-get-th1520-764a949de18e

Best regards,
-- 
Maurice Hieronymus <mhi@mailbox.org>

[PATCH 1/2] rust: clk: Add ExclusiveClk wrapper for clk_rate_exclusive_get

[Maurice Hieronymus via B4 Relay]

From: Maurice Hieronymus <mhi@mailbox.org>

Add Rust bindings for clk_rate_exclusive_get() and
clk_rate_exclusive_put().

Clk::rate_exclusive_get() consumes the Clk and returns an ExclusiveClk;
the matching put is issued from its Drop impl. ExclusiveClk derefs to
Clk so existing rate / prepare / enable APIs remain available on the
locked handle.

Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
---
 rust/kernel/clk.rs | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
index 7abbd0767d8c..8cda40cb01e4 100644
--- a/rust/kernel/clk.rs
+++ b/rust/kernel/clk.rs
@@ -249,6 +249,23 @@ pub fn set_rate(&self, rate: Hertz) -> Result {
             // [`clk_set_rate`].
             to_result(unsafe { bindings::clk_set_rate(self.as_raw(), rate.as_hz()) })
         }
+
+        /// Acquire exclusive control over the clock's rate.
+        ///
+        /// Consumes the [`Clk`] and returns an [`ExclusiveClk`] that releases the exclusivity
+        /// when dropped. While held, no other consumer may change the clock's rate.
+        ///
+        /// Equivalent to the kernel's [`clk_rate_exclusive_get`] API. Must not be called from
+        /// atomic context.
+        ///
+        /// [`clk_rate_exclusive_get`]:
+        /// https://docs.kernel.org/core-api/kernel-api.html#c.clk_rate_exclusive_get
+        pub fn rate_exclusive_get(self) -> Result<ExclusiveClk> {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_rate_exclusive_get`].
+            to_result(unsafe { bindings::clk_rate_exclusive_get(self.as_raw()) })?;
+            Ok(ExclusiveClk(self))
+        }
     }
 
     impl Drop for Clk {
@@ -329,6 +346,54 @@ fn deref(&self) -> &Clk {
             &self.0
         }
     }
+
+    /// A [`Clk`] with exclusive control over its rate.
+    ///
+    /// While an [`ExclusiveClk`] exists, no other consumer of the same clock may change its rate.
+    /// Obtained by calling [`Clk::rate_exclusive_get`]; the exclusivity is released automatically
+    /// when the value is dropped, after which the inner [`Clk`] is dropped as usual.
+    ///
+    /// # Invariants
+    ///
+    /// An [`ExclusiveClk`] instance owns a [`Clk`] for which `clk_rate_exclusive_get` has been
+    /// called and the matching `clk_rate_exclusive_put` has not yet been called.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use kernel::clk::{Clk, ExclusiveClk};
+    /// use kernel::device::Device;
+    /// use kernel::error::Result;
+    ///
+    /// fn lock_rate(dev: &Device) -> Result<ExclusiveClk> {
+    ///     let clk = Clk::get(dev, None)?;
+    ///     clk.prepare_enable()?;
+    ///     clk.rate_exclusive_get()
+    /// }
+    /// ```
+    ///
+    /// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html
+    pub struct ExclusiveClk(Clk);
+
+    // Make [`ExclusiveClk`] behave like [`Clk`].
+    impl Deref for ExclusiveClk {
+        type Target = Clk;
+
+        fn deref(&self) -> &Clk {
+            &self.0
+        }
+    }
+
+    impl Drop for ExclusiveClk {
+        fn drop(&mut self) {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_rate_exclusive_put`] and balances the [`clk_rate_exclusive_get`] call from
+            // [`Clk::rate_exclusive_get`].
+            unsafe {
+                bindings::clk_rate_exclusive_put(self.as_raw());
+            }
+        }
+    }
 }
 
 #[cfg(CONFIG_COMMON_CLK)]

-- 
2.51.2

Re: [PATCH 1/2] rust: clk: Add ExclusiveClk wrapper for clk_rate_exclusive_get

[Alice Ryhl]

On Tue, May 26, 2026 at 07:04:57PM +0200, Maurice Hieronymus via B4 Relay wrote:
> From: Maurice Hieronymus <mhi@mailbox.org>
> 
> Add Rust bindings for clk_rate_exclusive_get() and
> clk_rate_exclusive_put().
> 
> Clk::rate_exclusive_get() consumes the Clk and returns an ExclusiveClk;
> the matching put is issued from its Drop impl. ExclusiveClk derefs to
> Clk so existing rate / prepare / enable APIs remain available on the
> locked handle.
> 
> Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>

Overall looks okay to me. With below comments fixed:
Reviewed-by: Alice Ryhl <aliceryhl@google.com>

>  rust/kernel/clk.rs | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
> index 7abbd0767d8c..8cda40cb01e4 100644
> --- a/rust/kernel/clk.rs
> +++ b/rust/kernel/clk.rs
> @@ -249,6 +249,23 @@ pub fn set_rate(&self, rate: Hertz) -> Result {
>              // [`clk_set_rate`].
>              to_result(unsafe { bindings::clk_set_rate(self.as_raw(), rate.as_hz()) })
>          }
> +
> +        /// Acquire exclusive control over the clock's rate.
> +        ///
> +        /// Consumes the [`Clk`] and returns an [`ExclusiveClk`] that releases the exclusivity
> +        /// when dropped. While held, no other consumer may change the clock's rate.
> +        ///
> +        /// Equivalent to the kernel's [`clk_rate_exclusive_get`] API. Must not be called from
> +        /// atomic context.
> +        ///
> +        /// [`clk_rate_exclusive_get`]:
> +        /// https://docs.kernel.org/core-api/kernel-api.html#c.clk_rate_exclusive_get

Avoid the newline here. Links are long, and it's okay that they are
long. They must be on one line.

> +        pub fn rate_exclusive_get(self) -> Result<ExclusiveClk> {
> +            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
> +            // [`clk_rate_exclusive_get`].
> +            to_result(unsafe { bindings::clk_rate_exclusive_get(self.as_raw()) })?;
> +            Ok(ExclusiveClk(self))
> +        }
>      }
>  
>      impl Drop for Clk {
> @@ -329,6 +346,54 @@ fn deref(&self) -> &Clk {
>              &self.0
>          }
>      }
> +
> +    /// A [`Clk`] with exclusive control over its rate.
> +    ///
> +    /// While an [`ExclusiveClk`] exists, no other consumer of the same clock may change its rate.
> +    /// Obtained by calling [`Clk::rate_exclusive_get`]; the exclusivity is released automatically
> +    /// when the value is dropped, after which the inner [`Clk`] is dropped as usual.
> +    ///
> +    /// # Invariants
> +    ///
> +    /// An [`ExclusiveClk`] instance owns a [`Clk`] for which `clk_rate_exclusive_get` has been
> +    /// called and the matching `clk_rate_exclusive_put` has not yet been called.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// use kernel::clk::{Clk, ExclusiveClk};
> +    /// use kernel::device::Device;
> +    /// use kernel::error::Result;
> +    ///
> +    /// fn lock_rate(dev: &Device) -> Result<ExclusiveClk> {
> +    ///     let clk = Clk::get(dev, None)?;
> +    ///     clk.prepare_enable()?;
> +    ///     clk.rate_exclusive_get()
> +    /// }
> +    /// ```
> +    ///
> +    /// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html

Unused link.

> +    pub struct ExclusiveClk(Clk);
> +
> +    // Make [`ExclusiveClk`] behave like [`Clk`].
> +    impl Deref for ExclusiveClk {
> +        type Target = Clk;
> +
> +        fn deref(&self) -> &Clk {
> +            &self.0
> +        }
> +    }
> +
> +    impl Drop for ExclusiveClk {
> +        fn drop(&mut self) {
> +            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
> +            // [`clk_rate_exclusive_put`] and balances the [`clk_rate_exclusive_get`] call from
> +            // [`Clk::rate_exclusive_get`].
> +            unsafe {
> +                bindings::clk_rate_exclusive_put(self.as_raw());
> +            }

Nit: usually we format this with the semicolon outside the unsafe block.

unsafe { bindings::clk_rate_exclusive_put(self.as_raw()) };

Alice

[PATCH 2/2] pwm: th1520: Lock clock rate with clk_rate_exclusive_get

[Maurice Hieronymus via B4 Relay]

From: Maurice Hieronymus <mhi@mailbox.org>

The driver derives period and duty cycle from the clock rate read at
probe, so a later rate change would silently miscompute waveforms.
Switch to the new ExclusiveClk wrapper to hold the rate for the lifetime
of the driver data and drop the corresponding TODO.

Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
---
 drivers/pwm/pwm_th1520.rs | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs
index ddd44a5ce497..19e8621bc52c 100644
--- a/drivers/pwm/pwm_th1520.rs
+++ b/drivers/pwm/pwm_th1520.rs
@@ -22,7 +22,7 @@
 
 use core::ops::Deref;
 use kernel::{
-    clk::Clk,
+    clk::{Clk, ExclusiveClk},
     device::{Bound, Core, Device},
     devres,
     io::{
@@ -93,7 +93,7 @@ struct Th1520WfHw {
 struct Th1520PwmDriverData {
     #[pin]
     iomem: devres::Devres<IoMem<TH1520_PWM_REG_SIZE>>,
-    clk: Clk,
+    clk: ExclusiveClk,
 }
 
 impl pwm::PwmOps for Th1520PwmDriverData {
@@ -328,10 +328,8 @@ fn probe(
         let clk = Clk::get(dev, None)?;
 
         clk.prepare_enable()?;
+        let clk = clk.rate_exclusive_get()?;
 
-        // TODO: Get exclusive ownership of the clock to prevent rate changes.
-        // The Rust equivalent of `clk_rate_exclusive_get()` is not yet available.
-        // This should be updated once it is implemented.
         let rate_hz = clk.rate().as_hz();
         if rate_hz == 0 {
             dev_err!(dev, "Clock rate is zero\n");

-- 
2.51.2

Re: [PATCH 2/2] pwm: th1520: Lock clock rate with clk_rate_exclusive_get

[Alice Ryhl]

On Tue, May 26, 2026 at 07:04:58PM +0200, Maurice Hieronymus via B4 Relay wrote:
> From: Maurice Hieronymus <mhi@mailbox.org>
> 
> The driver derives period and duty cycle from the clock rate read at
> probe, so a later rate change would silently miscompute waveforms.
> Switch to the new ExclusiveClk wrapper to hold the rate for the lifetime
> of the driver data and drop the corresponding TODO.
> 
> Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH 0/2] rust: clk: Add ExclusiveClk and use it in pwm-th1520

[Maurice Hieronymus]

On Tue, 2026-05-26 at 19:04 +0200, Maurice Hieronymus via B4 Relay
wrote:
> Add a Rust binding for clk_rate_exclusive_get() /
> clk_rate_exclusive_put()
> and use it in pwm-th1520, which previously carried a TODO noting the
> missing binding.
> 
> Based on pwm/for-next.
> 
> Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
> ---
> Maurice Hieronymus (2):
>       rust: clk: Add ExclusiveClk wrapper for clk_rate_exclusive_get
>       pwm: th1520: Lock clock rate with clk_rate_exclusive_get
> 
>  drivers/pwm/pwm_th1520.rs |  8 +++---
>  rust/kernel/clk.rs        | 65
> +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+), 5 deletions(-)
> ---
> base-commit: 0e5e0db3e954b32a410ab4f74a4faac7a0e8889f
> change-id: 20260526-rate-exclusive-get-th1520-764a949de18e
> 
> Best regards,

Any opinions on this patch?