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Message-ID: <aEifXZnLxKd2wa0w@x1> Date: Tue, 10 Jun 2025 14:10:53 -0700 From: Drew Fustini <drew@...7.com> To: Michal Wilczynski <m.wilczynski@...sung.com> Cc: Uwe Kleine-König <ukleinek@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, Marek Szyprowski <m.szyprowski@...sung.com>, Benno Lossin <lossin@...nel.org>, Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org, rust-for-linux@...r.kernel.org, linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, linux-clk@...r.kernel.org Subject: Re: [PATCH v2 0/7] Rust Abstractions for PWM subsystem with TH1520 PWM driver On Tue, Jun 10, 2025 at 02:52:48PM +0200, Michal Wilczynski wrote: > This patch series introduces Rust support for the T-HEAD TH1520 PWM > controller and demonstrates its use for fan control on the Sipeed Lichee > Pi 4A board. > > The primary goal of this patch series is to introduce a basic set of > Rust abstractions for the Linux PWM subsystem. As a first user and > practical demonstration of these abstractions, the series also provides > a functional PWM driver for the T-HEAD TH1520 SoC. This allows control > of its PWM channels and ultimately enables temperature controlled fan > support for the Lichee Pi 4A board. This work aims to explore the use of > Rust for PWM drivers and lay a foundation for potential future > Rust based PWM drivers. > > The core of this series is a new rust/kernel/pwm.rs module that provides > abstractions for writing PWM chip provider drivers in Rust. This has > been significantly reworked from v1 based on extensive feedback. The key > features of the new abstraction layer include: > > - Ownership and Lifetime Management: The pwm::Chip wrapper is managed > by ARef, correctly tying its lifetime to its embedded struct device > reference counter. Chip registration is handled by a pwm::Registration > RAII guard, which guarantees that pwmchip_add is always paired with > pwmchip_remove, preventing resource leaks. > > - Modern and Safe API: The PwmOps trait is now based on the modern > waveform API (round_waveform_tohw, write_waveform, etc.) as recommended > by the subsystem maintainer. It is generic over a driver's > hardware specific data structure, moving all unsafe serialization logic > into the abstraction layer and allowing drivers to be written in 100% > safe Rust. > > - Ergonomics: The API provides safe, idiomatic wrappers for other PWM > types (State, Args, Device, etc.) and uses standard kernel error > handling patterns. > > The series is structured as follows: > - Rust PWM Abstractions: The new safe abstraction layer. > - TH1520 PWM Driver: A new Rust driver for the TH1520 SoC, built on > top of the new abstractions. > - Clock Fix: A necessary fix to the TH1520 clock driver to ensure bus > clocks remain enabled. > - Device Tree Bindings & Nodes: The remaining patches add the necessary > DT bindings and nodes for the TH1520 PWM controller, a thermal > sensor, and the PWM fan configuration for the Lichee Pi 4A board. > > Testing: > Tested on the TH1520 SoC. The fan works correctly. The duty/period > calculaties are correct. Fan starts slow when the chip is not hot and > gradually increases the speed when PVT reports higher temperatures. > > The patches are based on mainline, with some dependencies which are not > merged yet - platform Io support [1] and math wrapper [2]. > > Reference repository with all the patches together can be found on > github [3]. I'm trying to build your rust-next-pwm-working-fan-for-sending-v4 branch but I get this error: $ make W=1 LLVM=1 ARCH=riscv -j16 CALL scripts/checksyscalls.sh .pylintrc: warning: ignored by one of the .gitignore files UPD include/generated/utsversion.h CC init/version-timestamp.o KSYMS .tmp_vmlinux0.kallsyms.S AS .tmp_vmlinux0.kallsyms.o LD .tmp_vmlinux1 ld.lld: error: undefined symbol: rust_build_error referenced by pwm_th1520.4789668fc0b4e501-cgu.0 drivers/pwm/pwm_th1520.o:(<pwm_th1520::Th1520PwmDriverData as kernel::pwm::PwmOps>::get_state) in archive vmlinux.a referenced by pwm_th1520.4789668fc0b4e501-cgu.0 drivers/pwm/pwm_th1520.o:(<pwm_th1520::Th1520PwmDriverData as kernel::pwm::PwmOps>::write_waveform) in archive vmlinux.a referenced by pwm_th1520.4789668fc0b4e501-cgu.0 drivers/pwm/pwm_th1520.o:(<pwm_th1520::Th1520PwmDriverData as kernel::pwm::PwmOps>::write_waveform) in archive vmlinux.a make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1 make[1]: *** [/home/pdp7/linux/Makefile:1241: vmlinux] Error 2 make: *** [Makefile:248: __sub-make] Error 2 I've uploaded the config to: https://gist.github.com/pdp7/e2c34dd7e4349a54bd67b53254bd3a22 Thanks, Drew
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