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Message-ID: <epir3.2kxc5jzd28c@linaro.org>
Date: Fri, 07 Jun 2024 13:38:17 +0300
From: Manos Pitsidianakis <manos.pitsidianakis@...aro.org>
To: Viresh Kumar <viresh.kumar@...aro.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Bjö rn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, Alice Ryhl <aliceryhl@...gle.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org, Vincent Guittot <vincent.guittot@...aro.org>, Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>, rust-for-linux@...r.kernel.org, Manos Pitsidianakis <manos.pitsidianakis@...aro.org>, Erik Schilling <erik.schilling@...aro.org>, Alex Benné e <alex.bennee@...aro.org>, Joakim Bech <joakim.bech@...aro.org>, Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2 2/8] rust: Extend OPP bindings for the OPP table
On Fri, 07 Jun 2024 12:12, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>This extends OPP bindings with the bindings for the `struct opp_table`.
>
>Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
>---
> rust/kernel/opp.rs | 374 ++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 372 insertions(+), 2 deletions(-)
>
>diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
>index 9e5cf0412ed5..06f36845047f 100644
>--- a/rust/kernel/opp.rs
>+++ b/rust/kernel/opp.rs
>@@ -7,9 +7,9 @@
> //! C header: [`include/linux/pm_opp.h`](../../../../../../include/linux/pm_opp.h)
>
> use crate::{
>- bindings,
>+ bindings, cpumask,
> device::Device,
>- error::{code::*, to_result, Result},
>+ error::{code::*, from_err_ptr, to_result, Error, Result},
> types::{ARef, AlwaysRefCounted, Opaque},
> };
>
>@@ -31,6 +31,376 @@ pub fn new(freq: u64, u_volt: u64, level: u32, turbo: bool) -> Self {
> }
> }
>
>+/// OPP search types.
>+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
>+pub enum SearchType {
>+ /// Search for exact value.
>+ Exact,
>+ /// Search for highest value less than equal to value.
>+ Floor,
>+ /// Search for lowest value greater than equal to value.
>+ Ceil,
>+}
Seeing this enum made me think about memory layouts which are not stable
in Rust and can change between compilations unless they have a specific
`repr`.
Not related to this series directly, has there been discussion about
guaranteeing struct layouts in kernel APIs? It'd require a lot of things
to happen to cause a problem (multiple users of an API in the kernel in
separate compilation units maybe even compiled with different rustc
versions).
>+
>+/// Operating performance point (OPP) table.
>+///
>+/// # Invariants
>+///
>+/// The pointer stored in `Self` is non-null and valid for the lifetime of the ARef instance. In
>+/// particular, the ARef instance owns an increment on underlying object’s reference count.
>+pub struct Table {
>+ ptr: *mut bindings::opp_table,
>+ dev: ARef<Device>,
>+ em: bool,
>+ of: bool,
>+ cpumask: Option<cpumask::Cpumask>,
>+}
>+
>+// SAFETY: The fields of `Table` are safe to be used from any thread.
>+unsafe impl Send for Table {}
>+
>+// SAFETY: The fields of `Table` are safe to be referenced from any thread.
>+unsafe impl Sync for Table {}
>+
>+impl Table {
>+ /// Creates a new OPP table instance from raw pointer.
>+ ///
>+ /// # Safety
>+ ///
>+ /// Callers must ensure that `ptr` is valid and non-null.
>+ unsafe fn from_ptr(ptr: *mut bindings::opp_table, dev: ARef<Device>) -> Self {
>+ // SAFETY: By the safety requirements, ptr is valid and its refcount will be incremented.
>+ unsafe { bindings::dev_pm_opp_get_opp_table_ref(ptr) };
>+
>+ Self {
>+ ptr,
>+ dev,
>+ em: false,
>+ of: false,
>+ cpumask: None,
>+ }
>+ }
>+
>+ /// Find OPP table from device.
>+ pub fn from_dev(dev: ARef<Device>) -> Result<Self> {
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its safety
>+ // requirements. Refcount of the OPP table is incremented as well.
>+ let ptr = from_err_ptr(unsafe { bindings::dev_pm_opp_get_opp_table(dev.as_raw()) })?;
>+
>+ Ok(Self {
>+ ptr,
>+ dev: dev.clone(),
Clone is not probably not needed here, right? the argument value will be
dropped after this.
>+ em: false,
>+ of: false,
>+ cpumask: None,
>+ })
>+ }
>+
>+ /// Add device tree based OPP table for the device.
>+ #[cfg(CONFIG_OF)]
>+ pub fn from_of(dev: ARef<Device>, index: i32) -> Result<Self> {
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its safety
>+ // requirements. Refcount of the OPP table is incremented as well.
>+ to_result(unsafe { bindings::dev_pm_opp_of_add_table_indexed(dev.as_raw(), index) })?;
>+
>+ // Fetch the newly created table.
>+ let mut table = Self::from_dev(dev)?;
>+ table.of = true;
>+
>+ Ok(table)
>+ }
>+
>+ // Remove device tree based OPP table for the device.
>+ #[cfg(CONFIG_OF)]
>+ fn remove_of(&self) {
>+ // SAFETY: The requirements are satisfied by the existence of `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()) };
>+ }
>+
>+ /// Add device tree based OPP table for CPU devices.
>+ #[cfg(CONFIG_OF)]
>+ pub fn from_of_cpumask(dev: ARef<Device>, cpumask: &mut cpumask::Cpumask) -> Result<Self> {
>+ // SAFETY: The cpumask is valid and the returned ptr will be owned by the [`Table`] instance.
>+ to_result(unsafe { bindings::dev_pm_opp_of_cpumask_add_table(cpumask.as_ptr()) })?;
>+
>+ // Fetch the newly created table.
>+ let mut table = Self::from_dev(dev)?;
>+ // SAFETY: The `cpumask` is guaranteed by the C code to be valid.
>+ table.cpumask = Some(unsafe { cpumask::Cpumask::new(cpumask.as_mut_ptr()) });
>+
>+ Ok(table)
>+ }
>+
>+ // Remove device tree based OPP table for CPU devices.
>+ #[cfg(CONFIG_OF)]
>+ fn remove_of_cpumask(&self, cpumask: &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_ptr()) };
>+ }
>+
>+ /// Returns the number of OPPs 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 of the OPPs in the table.
>+ pub fn max_clock_latency(&self) -> u64 {
>+ // 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 of the OPPs in the table.
>+ pub fn max_volt_latency(&self) -> u64 {
>+ // 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 of the OPPs in the table.
>+ pub fn max_transition_latency(&self) -> u64 {
>+ // 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.
>+ pub fn suspend_freq(&self) -> u64 {
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its safety
>+ // requirements.
>+ unsafe { bindings::dev_pm_opp_get_suspend_opp_freq(self.dev.as_raw()) }
>+ }
>+
>+ /// Synchronizes regulators used by the OPP table.
>+ 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.
>+ pub fn sharing_cpus(dev: ARef<Device>, cpumask: &mut cpumask::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_mut_ptr())
>+ })
>+ }
>+
>+ /// Sets sharing CPUs.
>+ pub fn set_sharing_cpus(&self, cpumask: &cpumask::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_ptr())
>+ })
>+ }
>+
>+ /// Gets sharing CPUs from Device tree.
>+ #[cfg(CONFIG_OF)]
>+ pub fn of_sharing_cpus(dev: ARef<Device>, cpumask: &mut cpumask::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_mut_ptr())
>+ })
>+ }
>+
>+ /// Updates the voltage value for an OPP.
>+ pub fn adjust_voltage(
>+ &self,
>+ freq: u64,
>+ u_volt: u64,
>+ u_volt_min: u64,
>+ u_volt_max: u64,
>+ ) -> 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,
>+ u_volt,
>+ u_volt_min,
>+ u_volt_max,
>+ )
>+ })
>+ }
>+
>+ /// Sets a matching OPP based on frequency.
>+ pub fn set_rate(&self, freq: u64) -> 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) })
>+ }
>+
>+ /// Sets exact OPP.
>+ pub fn set_opp(&self, opp: ARef<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_mut_ptr()) })
>+ }
>+
>+ /// Finds OPP based on frequency.
>+ pub fn opp_from_freq(
>+ &self,
>+ mut freq: u64,
>+ available: Option<bool>,
>+ index: Option<u32>,
>+ stype: SearchType,
>+ ) -> Result<ARef<OPP>> {
>+ let rdev = self.dev.as_raw();
>+ let index = index.unwrap_or(0);
>+
>+ 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 ptr will be owned by the new [`OPP`]
>+ // instance.
>+ unsafe {
>+ bindings::dev_pm_opp_find_freq_exact_indexed(rdev, freq, index, available)
>+ }
>+ } else {
>+ return Err(EINVAL);
>+ }
>+ }
>+
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its
>+ // safety requirements. The returned ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Ceil => unsafe {
>+ bindings::dev_pm_opp_find_freq_ceil_indexed(rdev, &mut freq as *mut u64, index)
>+ },
>+
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its
>+ // safety requirements. The returned ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Floor => unsafe {
>+ bindings::dev_pm_opp_find_freq_floor_indexed(rdev, &mut freq as *mut u64, index)
>+ },
>+ })?;
>+
>+ // SAFETY: The `ptr` is guaranteed by the C code to be valid.
>+ unsafe { OPP::from_ptr_owned(ptr) }
>+ }
>+
>+ /// Finds OPP based on level.
>+ pub fn opp_from_level(&self, mut level: u32, stype: SearchType) -> Result<ARef<OPP>> {
>+ let rdev = 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 ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Exact => unsafe { bindings::dev_pm_opp_find_level_exact(rdev, level) },
>+
Minor style comment, the empty lines between match patterns are unusual
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its
>+ // safety requirements. The returned ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Ceil => unsafe {
>+ bindings::dev_pm_opp_find_level_ceil(rdev, &mut level as *mut u32)
>+ },
>+
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its
>+ // safety requirements. The returned ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Floor => unsafe {
>+ bindings::dev_pm_opp_find_level_floor(rdev, &mut level as *mut u32)
>+ },
>+ })?;
>+
>+ // SAFETY: The `ptr` is guaranteed by the C code to be valid.
>+ unsafe { OPP::from_ptr_owned(ptr) }
>+ }
>+
>+ /// Finds OPP based on bandwidth.
>+ pub fn opp_from_bw(&self, mut bw: u32, index: i32, stype: SearchType) -> Result<ARef<OPP>> {
>+ let rdev = 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 ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Ceil => unsafe {
>+ bindings::dev_pm_opp_find_bw_ceil(rdev, &mut bw as *mut u32, index)
>+ },
>+
>+ // SAFETY: The requirements are satisfied by the existence of `Device` and its
>+ // safety requirements. The returned ptr will be owned by the new [`OPP`] instance.
>+ SearchType::Floor => unsafe {
>+ bindings::dev_pm_opp_find_bw_floor(rdev, &mut bw as *mut u32, index)
>+ },
>+ })?;
>+
>+ // SAFETY: The `ptr` is guaranteed by the C code to be valid.
>+ unsafe { OPP::from_ptr_owned(ptr) }
>+ }
>+
>+ /// Enable the OPP.
>+ pub fn enable_opp(&self, freq: u64) -> 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) })
>+ }
>+
>+ /// Disable the OPP.
>+ pub fn disable_opp(&self, freq: u64) -> 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) })
>+ }
>+
>+ /// Registers with Energy model.
>+ #[cfg(CONFIG_OF)]
>+ pub fn of_register_em(&mut self, cpumask: &mut cpumask::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_mut_ptr())
>+ })?;
>+
>+ self.em = true;
>+ Ok(())
>+ }
>+
>+ // Unregisters with Energy model.
>+ #[cfg(CONFIG_OF)]
>+ 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)]
>+ {
>+ if self.em {
>+ self.of_unregister_em();
>+ }
>+
>+ if self.of {
>+ self.remove_of();
>+ } else if let Some(cpumask) = &self.cpumask {
>+ self.remove_of_cpumask(cpumask);
>+ }
>+ }
>+ }
>+}
>+
> /// Operating performance point (OPP).
> ///
> /// # Invariants
>--
>2.31.1.272.g89b43f80a514
>
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