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

[Sunil V L]

On Tue, Jul 28, 2026 at 6:24 PM Sunil V L <sunilvl at oss.qualcomm.com> wrote:
>
> On Tue, Jul 28, 2026 at 5:24 PM Peixin Xie
> <peixin.xie at linux.spacemit.com> 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 at vger.kernel.org
> > Acked-by: Sudeep Holla <sudeep.holla at kernel.org>
> > Reviewed-by: Yixun Lan <dlan at kernel.org>
> > Signed-off-by: Peixin Xie <peixin.xie at linux.spacemit.com>
> > ---
> > 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@linux.spacemit.com
> > ---
> >  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?
>
It appears there is an issue with the HTML version regarding the
chapter numbering. I have reported this to the documentation team. In
the meantime, I recommend using the PDF version as the reference for
any citations.

Thanks,
Sunil