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Message-Id: <1792467a772b7a8355c6d0cb0cbacfbffff08afd.1712314032.git.viresh.kumar@linaro.org>
Date: Fri, 5 Apr 2024 16:39:40 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
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>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...sung.com>,
Alice Ryhl <aliceryhl@...gle.com>
Cc: 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 Bennée <alex.bennee@...aro.org>,
Joakim Bech <joakim.bech@...aro.org>,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/3] cpufreq: Add Rust based cpufreq-dt driver
This commit adds a Rust based cpufreq-dt driver, which covers most of
the functionality of the existing C based driver. Only a handful of
things are left, like fetching platform data from cpufreq-dt-platdev.c.
This is tested with the help of QEMU for now and switching of
frequencies work as expected.
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
drivers/cpufreq/Kconfig | 12 ++
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/rcpufreq_dt.rs | 264 +++++++++++++++++++++++++++++++++
3 files changed, 277 insertions(+)
create mode 100644 drivers/cpufreq/rcpufreq_dt.rs
diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 94e55c40970a..eb9359bd3c5c 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -217,6 +217,18 @@ config CPUFREQ_DT
If in doubt, say N.
+config CPUFREQ_DT_RUST
+ tristate "Rust based Generic DT based cpufreq driver"
+ depends on HAVE_CLK && OF && RUST
+ select CPUFREQ_DT_PLATDEV
+ select PM_OPP
+ help
+ This adds a Rust based generic DT based cpufreq driver for frequency
+ management. It supports both uniprocessor (UP) and symmetric
+ multiprocessor (SMP) systems.
+
+ If in doubt, say N.
+
config CPUFREQ_DT_PLATDEV
tristate "Generic DT based cpufreq platdev driver"
depends on OF
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 8d141c71b016..4981d908b803 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_CPU_FREQ_GOV_COMMON) += cpufreq_governor.o
obj-$(CONFIG_CPU_FREQ_GOV_ATTR_SET) += cpufreq_governor_attr_set.o
obj-$(CONFIG_CPUFREQ_DT) += cpufreq-dt.o
+obj-$(CONFIG_CPUFREQ_DT_RUST) += rcpufreq_dt.o
obj-$(CONFIG_CPUFREQ_DT_PLATDEV) += cpufreq-dt-platdev.o
# Traces
diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
new file mode 100644
index 000000000000..d29182eba75e
--- /dev/null
+++ b/drivers/cpufreq/rcpufreq_dt.rs
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust based implementation of the cpufreq-dt driver.
+
+use core::{format_args, ptr};
+
+use kernel::{
+ b_str, bindings, c_str, cpufreq, define_of_id_table,
+ device::{self, Device, RawDevice},
+ error::{code::*, to_result},
+ fmt,
+ macros::vtable,
+ module_platform_driver, of, opp, platform,
+ prelude::*,
+ str::CString,
+ sync::Arc,
+};
+
+// Finds exact supply name from the OF node.
+fn find_supply_name_exact(np: *mut bindings::device_node, name: &str) -> Option<CString> {
+ let sname = CString::try_from_fmt(fmt!("{}-supply", name)).ok()?;
+
+ // SAFETY: The OF node is guaranteed by the C code to be valid.
+ let pp = unsafe { bindings::of_find_property(np, sname.as_ptr() as *mut _, ptr::null_mut()) };
+ if pp.is_null() {
+ None
+ } else {
+ CString::try_from_fmt(fmt!("{}", name)).ok()
+ }
+}
+
+// Finds supply name for the CPU from DT.
+fn find_supply_names(dev: &Device, cpu: u32) -> Option<Vec<CString>> {
+ // SAFETY: The requirements are satisfied by the existence of `RawDevice` and its safety
+ // requirements. The OF node is guaranteed by the C code to be valid or NULL and
+ // `of_node_get()` handles both the cases safely.
+ let np = unsafe { bindings::of_node_get((*dev.raw_device()).of_node) };
+ if np.is_null() {
+ return None;
+ }
+
+ // Try "cpu0" for older DTs.
+ let mut name = if cpu == 0 {
+ find_supply_name_exact(np, "cpu0")
+ } else {
+ None
+ };
+
+ if name.is_none() {
+ name = find_supply_name_exact(np, "cpu");
+ }
+
+ // SAFETY: It is safe to drop reference to the OF node we just took.
+ unsafe { bindings::of_node_put(np) };
+
+ match name {
+ Some(name) => {
+ let mut list = Vec::try_with_capacity(1).ok()?;
+ list.try_push(name).ok()?;
+
+ // SAFETY: The slice is fully initialized now.
+ Some(list)
+ }
+
+ None => None,
+ }
+}
+
+// Represents the cpufreq dt device.
+struct CPUFreqDTDevice {
+ opp_table: opp::Table,
+ freq_table: opp::FreqTable,
+ #[allow(dead_code)]
+ config: Option<opp::Config<Self>>,
+ #[allow(dead_code)]
+ clk: cpufreq::Clk,
+}
+
+#[vtable]
+impl opp::ConfigOps for CPUFreqDTDevice {}
+
+#[vtable]
+impl cpufreq::DriverOps for CPUFreqDTDevice {
+ type PData = Arc<Self>;
+
+ fn init(policy: &mut cpufreq::Policy) -> Result<Self::PData> {
+ let cpu = policy.cpu();
+
+ // SAFETY: It is safe to call `get_cpu_device()` for any CPU.
+ let dev = unsafe { bindings::get_cpu_device(cpu) };
+ if dev.is_null() {
+ return Err(ENODEV);
+ }
+
+ // SAFETY: `dev` is valid, non-null, and has a non-zero reference count.
+ let dev = unsafe { Device::new(dev) };
+
+ policy.set_cpus(cpu);
+
+ let config = if let Some(names) = find_supply_names(&dev, cpu) {
+ let mut config = opp::Config::<Self>::new();
+ config.set_regulator_names(names)?;
+ config.set(&dev)?;
+ Some(config)
+ } else {
+ None
+ };
+
+ // Get OPP-sharing information from "operating-points-v2" bindings.
+ let fallback = match opp::Table::of_sharing_cpus(&dev, policy.cpus()) {
+ Ok(_) => false,
+ Err(e) => {
+ if e != ENOENT {
+ return Err(e);
+ }
+
+ // "operating-points-v2" not supported. If the platform hasn't
+ // set sharing CPUs, fallback to all CPUs share the `Policy`
+ // for backward compatibility.
+ opp::Table::sharing_cpus(&dev, policy.cpus()).is_err()
+ }
+ };
+
+ // Initialize OPP tables for all policy cpus.
+ //
+ // For platforms not using "operating-points-v2" bindings, we do this
+ // before updating policy cpus. Otherwise, we will end up creating
+ // duplicate OPPs for the CPUs.
+ //
+ // OPPs might be populated at runtime, don't fail for error here unless
+ // it is -EPROBE_DEFER.
+ let mut opp_table = match opp::Table::from_of_cpumask(&dev, policy.cpus()) {
+ Ok(table) => table,
+ Err(e) => {
+ if e == EPROBE_DEFER {
+ return Err(e);
+ }
+
+ // The table is added dynamically ?
+ opp::Table::from_dev(&dev)?
+ }
+ };
+
+ // The OPP table must be initialized, statically or dynamically, by this point.
+ opp_table.opp_count()?;
+
+ // Set sharing cpus for fallback scenario.
+ if fallback {
+ policy.set_all_cpus();
+ opp_table.set_sharing_cpus(policy.cpus())?;
+ }
+
+ let mut transition_latency = opp_table.max_transition_latency() as u32;
+ if transition_latency == 0 {
+ transition_latency = cpufreq::ETERNAL_LATENCY;
+ }
+
+ let freq_table = opp_table.to_cpufreq_table()?;
+ policy.set_freq_table(freq_table.table());
+ policy.set_dvfs_possible_from_any_cpu();
+ policy.set_suspend_freq((opp_table.suspend_freq() / 1000) as u32);
+ policy.set_transition_latency(transition_latency);
+ let clk = policy.set_clk(&dev, None)?;
+
+ Ok(Arc::try_new(CPUFreqDTDevice {
+ opp_table,
+ config,
+ freq_table,
+ clk,
+ })?)
+ }
+
+ fn exit(_policy: &mut cpufreq::Policy, _data: Option<Self::PData>) -> Result<()> {
+ Ok(())
+ }
+
+ fn online(_policy: &mut cpufreq::Policy) -> Result<()> {
+ // We did light-weight tear down earlier, nothing to do here.
+ Ok(())
+ }
+
+ fn offline(_policy: &mut cpufreq::Policy) -> Result<()> {
+ // Preserve policy->data and don't free resources on light-weight
+ // tear down.
+ Ok(())
+ }
+
+ fn suspend(policy: &mut cpufreq::Policy) -> Result<()> {
+ // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+ // use it now.
+ to_result(unsafe { bindings::cpufreq_generic_suspend(policy.as_ptr()) })
+ }
+
+ fn verify(data: &mut cpufreq::PolicyData) -> Result<()> {
+ // SAFETY: By the type invariants, we know that `data` owns a reference received from the C
+ // code, so it is safe to use it now.
+ to_result(unsafe { bindings::cpufreq_generic_frequency_table_verify(data.as_ptr()) })
+ }
+
+ fn target_index(policy: &mut cpufreq::Policy, index: u32) -> Result<()> {
+ let data = match policy.data::<Self::PData>() {
+ Some(data) => data,
+ None => return Err(ENOENT),
+ };
+
+ let freq = data.freq_table.freq(index.try_into().unwrap())? as u64;
+ data.opp_table.set_rate(freq * 1000)
+ }
+
+ fn get(policy: &mut cpufreq::Policy) -> Result<u32> {
+ // SAFETY: It is safe to call `cpufreq_generic_get()` for policy's CPU.
+ Ok(unsafe { bindings::cpufreq_generic_get(policy.cpu()) })
+ }
+
+ fn set_boost(_policy: &mut cpufreq::Policy, _state: i32) -> Result<()> {
+ Ok(())
+ }
+
+ fn register_em(policy: &mut cpufreq::Policy) {
+ // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+ // use it now.
+ unsafe { bindings::cpufreq_register_em_with_opp(policy.as_ptr()) };
+ }
+}
+
+type DeviceData = device::Data<cpufreq::Registration<CPUFreqDTDevice>, (), ()>;
+
+struct CPUFreqDTDriver;
+
+impl platform::Driver for CPUFreqDTDriver {
+ type Data = Arc<DeviceData>;
+
+ define_of_id_table! {(), [
+ (of::DeviceId::Compatible(b_str!("operating-points-v2")), None),
+ ]}
+
+ fn probe(_dev: &mut platform::Device, _id_info: Option<&Self::IdInfo>) -> Result<Self::Data> {
+ let data = Arc::<DeviceData>::from(kernel::new_device_data!(
+ cpufreq::Registration::new(),
+ (),
+ (),
+ "CPUFreqDT::Registration"
+ )?);
+ let flags = cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV;
+ let boost = true;
+
+ data.registrations()
+ .ok_or(ENXIO)?
+ .as_pinned_mut()
+ .register(c_str!("cpufreq-dt"), (), flags, boost)?;
+
+ pr_info!("CPUFreq DT driver registered\n");
+
+ Ok(data)
+ }
+}
+
+module_platform_driver! {
+ type: CPUFreqDTDriver,
+ name: "cpufreq_dt",
+ author: "Viresh Kumar <viresh.kumar@...aro.org>",
+ description: "Generic CPUFreq DT driver",
+ license: "GPL v2",
+}
--
2.31.1.272.g89b43f80a514
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