kernel/linux.git/drivers/clocksource/timer-riscv.c, branch v6.12.80

riscv: clocksource: Fix stimecmp update hazard on RV32

2026-01-30T09:28:41+00:00

[ Upstream commit eaa9bb1d39d59e7c17b06cec12622b7c586ab629 ] On RV32, updating the 64-bit stimecmp (or vstimecmp) CSR requires two separate 32-bit writes. A race condition exists if the timer triggers during these two writes. The RISC-V Privileged Specification (e.g., Section 3.2.1 for mtimecmp) recommends a specific 3-step sequence to avoid spurious interrupts when updating 64-bit comparison registers on 32-bit systems: 1. Set the low-order bits (stimecmp) to all ones (ULONG_MAX). 2. Set the high-order bits (stimecmph) to the desired value. 3. Set the low-order bits (stimecmp) to the desired value. Current implementation writes the LSB first without ensuring a future value, which may lead to a transient state where the 64-bit comparison is incorrectly evaluated as "expired" by the hardware. This results in spurious timer interrupts. This patch adopts the spec-recommended 3-step sequence to ensure the intermediate 64-bit state is never smaller than the current time. Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available") Signed-off-by: Naohiko Shimizu Reviewed-by: Anup Patel Link: https://patch.msgid.link/20260104135938.524-2-naohiko.shimizu@gmail.com Signed-off-by: Paul Walmsley Signed-off-by: Sasha Levin

clocksource/drivers/timer-riscv: Stop stimecmp when cpu hotplug

2025-05-29T09:02:14+00:00

[ Upstream commit 70c93b026ed07078e933583591aa9ca6701cd9da ] Stop the timer when the cpu is going to be offline otherwise the timer interrupt may be pending while performing power-down. Suggested-by: Anup Patel Link: https://lore.kernel.org/lkml/20240829033904.477200-3-nick.hu@sifive.com/T/#u Signed-off-by: Nick Hu Reviewed-by: Anup Patel Acked-by: Daniel Lezcano Link: https://lore.kernel.org/r/20250219114135.27764-3-nick.hu@sifive.com Signed-off-by: Alexandre Ghiti Signed-off-by: Sasha Levin

Merge tag 'timers-core-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-03-23T21:42:45+00:00

Pull more clocksource updates from Thomas Gleixner: "A set of updates for clocksource and clockevent drivers: - A fix for the prescaler of the ARM global timer where the prescaler mask define only covered 4 bits while it is actully 8 bits wide. This obviously restricted the possible range of prescaler adjustments - A fix for the RISC-V timer which prevents a timer interrupt being raised while the timer is initialized - A set of device tree updates to support new system on chips in various drivers - Kernel-doc and other cleanups all over the place" * tag 'timers-core-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: clocksource/drivers/timer-riscv: Clear timer interrupt on timer initialization dt-bindings: timer: Add support for cadence TTC PWM clocksource/drivers/arm_global_timer: Simplify prescaler register access clocksource/drivers/arm_global_timer: Guard against division by zero clocksource/drivers/arm_global_timer: Make gt_target_rate unsigned long dt-bindings: timer: add Ralink SoCs system tick counter clocksource: arm_global_timer: fix non-kernel-doc comment clocksource/drivers/arm_global_timer: Remove stray tab clocksource/drivers/arm_global_timer: Fix maximum prescaler value clocksource/drivers/imx-sysctr: Add i.MX95 support clocksource/drivers/imx-sysctr: Drop use global variables dt-bindings: timer: nxp,sysctr-timer: support i.MX95 dt-bindings: timer: renesas: ostm: Document RZ/Five SoC dt-bindings: timer: renesas,tmu: Document input capture interrupt clocksource/drivers/ti-32K: Fix misuse of "/**" comment clocksource/drivers/stm32: Fix all kernel-doc warnings dt-bindings: timer: exynos4210-mct: Add google,gs101-mct compatible clocksource/drivers/imx: Fix -Wunused-but-set-variable warning

clocksource/drivers/timer-riscv: Clear timer interrupt on timer initialization

2024-03-13T11:08:59+00:00

In the RISC-V specification, the stimecmp register doesn't have a default value. To prevent the timer interrupt from being triggered during timer initialization, clear the timer interrupt by writing stimecmp with a maximum value. Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available") Cc: Signed-off-by: Ley Foon Tan Reviewed-by: Samuel Holland Tested-by: Samuel Holland Reviewed-by: Atish Patra Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240306172330.255844-1-leyfoon.tan@starfivetech.com

clocksource: extend the max_delta_ns of timer-riscv and timer-clint to ULONG_MAX

2024-01-23T02:09:49+00:00

When registering the riscv-timer or clint-timer as a clock_event device, the driver needs to specify the value of max_delta_ticks. This value directly influences the max_delta_ns, which represents the maximum time interval for configuring subsequent clock events. Currently, both riscv-timer and clint-timer are set with a max_delta_ticks value of 0x7fff_ffff. When the timer operates at a high frequency, this values limists the system to sleep only for a short time. For the 1GHz case, the sleep cannot exceed two seconds. To address this limitation, refer to other timer implementations to extend it to 2^(bit-width of the timer) - 1. Because the bit-width of $mtimecmp is 64bit, this value becomes ULONG_MAX (0xffff_ffff_ffff_ffff). Signed-off-by: Vincent Chen Link: https://lore.kernel.org/r/20230905070945.404653-1-vincent.chen@sifive.com Signed-off-by: Palmer Dabbelt

clocksource/timer-riscv: Add riscv_clock_shutdown callback

2023-12-27T14:37:11+00:00

Add clocksource detach/shutdown callback to disable RISC-V timer interrupt when switching out riscv timer as clock source Signed-off-by: Joshua Yeong Reviewed-by: Anup Patel Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20231116105312.4800-1-joshua.yeong@starfivetech.com

Merge tag 'riscv-for-linus-6.7-mw2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

2023-11-10T17:23:17+00:00

Pull more RISC-V updates from Palmer Dabbelt: - Support for handling misaligned accesses in S-mode - Probing for misaligned access support is now properly cached and handled in parallel - PTDUMP now reflects the SW reserved bits, as well as the PBMT and NAPOT extensions - Performance improvements for TLB flushing - Support for many new relocations in the module loader - Various bug fixes and cleanups * tag 'riscv-for-linus-6.7-mw2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (51 commits) riscv: Optimize bitops with Zbb extension riscv: Rearrange hwcap.h and cpufeature.h drivers: perf: Do not broadcast to other cpus when starting a counter drivers: perf: Check find_first_bit() return value of: property: Add fw_devlink support for msi-parent RISC-V: Don't fail in riscv_of_parent_hartid() for disabled HARTs riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings riscv: Don't use PGD entries for the linear mapping RISC-V: Probe misaligned access speed in parallel RISC-V: Remove __init on unaligned_emulation_finish() RISC-V: Show accurate per-hart isa in /proc/cpuinfo RISC-V: Don't rely on positional structure initialization riscv: Add tests for riscv module loading riscv: Add remaining module relocations riscv: Avoid unaligned access when relocating modules riscv: split cache ops out of dma-noncoherent.c riscv: Improve flush_tlb_kernel_range() riscv: Make __flush_tlb_range() loop over pte instead of flushing the whole tlb riscv: Improve flush_tlb_range() for hugetlb pages riscv: Improve tlb_flush() ...

riscv: Rearrange hwcap.h and cpufeature.h

2023-11-09T18:15:51+00:00

Now hwcap.h and cpufeature.h are mutually including each other, and most of the variable/API declarations in hwcap.h are implemented in cpufeature.c, so, it's better to move them into cpufeature.h and leave only macros for ISA extension logical IDs in hwcap.h. BTW, the riscv_isa_extension_mask macro is not used now, so this patch removes it. Suggested-by: Andrew Jones Signed-off-by: Xiao Wang Reviewed-by: Andrew Jones Link: https://lore.kernel.org/r/20231031064553.2319688-2-xiao.w.wang@intel.com Signed-off-by: Palmer Dabbelt

Merge tag 'riscv-for-linus-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

2023-11-08T17:21:18+00:00

Pull RISC-V updates from Palmer Dabbelt: - Support for cbo.zero in userspace - Support for CBOs on ACPI-based systems - A handful of improvements for the T-Head cache flushing ops - Support for software shadow call stacks - Various cleanups and fixes * tag 'riscv-for-linus-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (31 commits) RISC-V: hwprobe: Fix vDSO SIGSEGV riscv: configs: defconfig: Enable configs required for RZ/Five SoC riscv: errata: prefix T-Head mnemonics with th. riscv: put interrupt entries into .irqentry.text riscv: mm: Update the comment of CONFIG_PAGE_OFFSET riscv: Using TOOLCHAIN_HAS_ZIHINTPAUSE marco replace zihintpause riscv/mm: Fix the comment for swap pte format RISC-V: clarify the QEMU workaround in ISA parser riscv: correct pt_level name via pgtable_l5/4_enabled RISC-V: Provide pgtable_l5_enabled on rv32 clocksource: timer-riscv: Increase rating of clock_event_device for Sstc clocksource: timer-riscv: Don't enable/disable timer interrupt lkdtm: Fix CFI_BACKWARD on RISC-V riscv: Use separate IRQ shadow call stacks riscv: Implement Shadow Call Stack riscv: Move global pointer loading to a macro riscv: Deduplicate IRQ stack switching riscv: VMAP_STACK overflow detection thread-safe RISC-V: cacheflush: Initialize CBO variables on ACPI systems RISC-V: ACPI: RHCT: Add function to get CBO block sizes ...

clocksource: timer-riscv: Increase rating of clock_event_device for Sstc

2023-11-01T02:15:49+00:00

When Sstc is available the RISC-V timer clock_event_device should be the preferred clock_event_device hence we increase clock_event_device rating for Sstc. Signed-off-by: Anup Patel Reviewed-by: Conor Dooley Acked-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20230710131902.1459180-3-apatel@ventanamicro.com Signed-off-by: Palmer Dabbelt