Re: [PATCH v2] riscv: acpi: Handle LPI architectural context loss flags

[Sunil V L]

On Tue, Jul 28, 2026 at 5:24 PM Peixin Xie
<peixin.xie@xxxxxxxxxxxxxxxxxx> wrote:
>
> Commit 4785aa802853 ("cpuidle, ACPI: Evaluate LPI arch_flags for
> broadcast timer") replaced the generic nonzero check for LPI
> architectural context loss flags with arch_get_idle_state_flags().
> RISC-V does not implement the helper, so it falls back to the stub
> that returns 0. Consequently, CPUIDLE_FLAG_TIMER_STOP is not set when
> an LPI state loses the hart timer context, preventing cpuidle from
> using a broadcast timer for that state.
>
> Implement the RISC-V helper and map the hart timer context loss flag
> to CPUIDLE_FLAG_TIMER_STOP.
>
> Fixes: 4785aa802853 ("cpuidle, ACPI: Evaluate LPI arch_flags for broadcast timer")
> Cc: stable@xxxxxxxxxxxxxxx
> Acked-by: Sudeep Holla <sudeep.holla@xxxxxxxxxx>
> Reviewed-by: Yixun Lan <dlan@xxxxxxxxxx>
> Signed-off-by: Peixin Xie <peixin.xie@xxxxxxxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Correct the FFH specification reference to Chapter 2.1.1.2,
>   Table 3, as suggested by Yixun.
> - Link to v1: https://patch.msgid.link/20260728-riscv-acpi-lpi-timer-v1-1-c722bce01e48@xxxxxxxxxxxxxxxxxx
> ---
>  arch/riscv/include/asm/acpi.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index 26ab37c171bc..2643e28fc08c 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -12,6 +12,8 @@
>  #ifndef _ASM_ACPI_H
>  #define _ASM_ACPI_H
>
> +#include <linux/cpuidle.h>
> +
>  /* Basic configuration for ACPI */
>  #ifdef CONFIG_ACPI
>
> @@ -67,6 +69,23 @@ int acpi_get_riscv_isa(struct acpi_table_header *table,
>
>  void acpi_get_cbo_block_size(struct acpi_table_header *table, u32 *cbom_size,
>                              u32 *cboz_size, u32 *cbop_size);
> +
> +/*
> + * RISC-V Functional Fixed Hardware Specification Version v1.0.1,
> + * Chapter 2.1.1.2. Arch. Context Lost Flags, Table 3
>
Isn't it Chapter 3.1.2, Table 4?

> + */
> +#define RISCV_LPI_HART_TIMER_CTXT_LOST         BIT(0)
> +
> +static inline unsigned int arch_get_idle_state_flags(u32 arch_flags)
> +{
> +       if (arch_flags & RISCV_LPI_HART_TIMER_CTXT_LOST)
> +               return CPUIDLE_FLAG_TIMER_STOP;
> +
> +       return 0;
> +}
> +
> +#define arch_get_idle_state_flags arch_get_idle_state_flags
> +
Otherwise, LGTM.

Reviewed-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>