SiFive FU540 and FU740 PRCI clock and reset controllers
Controls the on-chip PLLs, clock gates, and reset lines (the PRCI block) inside SiFive's FU540 and FU740 RISC-V system-on-chip processors, which power the HiFive Unleashed and HiFive Unmatched developer boards that have been the most widely available RISC-V Linux workstations from 2018 onward.
recommendation
It should stay in the kernel because the hardware it serves, SiFive's FU540 and FU740 RISC-V SoCs used in HiFive Unleashed and HiFive Unmatched developer boards, is still being sold new in 2025 and remains a reference platform for RISC-V Linux work. The code is actively maintained, with a refactor series landing in 2022 and substantive commits as recently as September 2025, and there is no generic replacement because PRCI clock control is specific to these SoCs.
repository signals
sources
- git.kernel.org
The upstream driver binds to SiFive PRCI blocks for `sifive,fu540-c000-prci` and `sifive,fu740-c000-prci`, so this directory covers SiFive FU540/FU740 SoC clock/reset hardware.
- lore.kernel.org
linux-clk carried a multi-patch 2022 cleanup/refactor series for `clk: sifive`, showing real upstream maintenance rather than abandonment.
- sifive.com
SiFive's HiFive Unmatched Rev B page advertises a FU740-based board with a 'Buy Now' flow and says boards are available through Mouser, indicating the hardware family was still being sold new in the 2025 timeframe.
- docs.u-boot.org
Current U-Boot documentation for the FU740-based HiFive Unmatched explicitly lists the SiFive PRCI clock driver in mainline support, showing ongoing software enablement and present-day niche deployment.
codex reasoning notes (technical)
Keep: prompt metadata already shows 13 substantive commits in the last 5 years with a most recent substantive touch on 2025-09-08, so this is not a dormant candidate. `lore_file_timeline` on the source file showed maintenance/refactor traffic and no removal/deprecation thread; the cited lore URL came from that MCP call. The kernel.org source URL is canonical recall used to confirm the driver only serves FU540/FU740 PRCI blocks. The SiFive board page and U-Boot page were obtained via `web.search_query`; together they indicate FU740 hardware remained commercially available in the 2025 window and is still used in low-volume RISC-V dev platforms. No natural replacement driver exists because this is SoC-specific PRCI clock control, not a superseded generic peripheral driver.