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

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

[Peixin Xie]

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@vger.kernel.org
Acked-by: Sudeep Holla <sudeep.holla@kernel.org>
Reviewed-by: Yixun Lan <dlan@kernel.org>
Signed-off-by: Peixin Xie <peixin.xie@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
+ */
+#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
+
 #else
 static inline void acpi_init_rintc_map(void) { }
 static inline struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)

---
base-commit: 1d6f0a217c662693d2307ee06851cb4bfcbf9529
change-id: 20260727-riscv-acpi-lpi-timer-6f1739a6c831

Best regards,
--  
Peixin Xie <peixin.xie@linux.spacemit.com>

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@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@vger.kernel.org
> Acked-by: Sudeep Holla <sudeep.holla@kernel.org>
> Reviewed-by: Yixun Lan <dlan@kernel.org>
> Signed-off-by: Peixin Xie <peixin.xie@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?

> + */
> +#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@oss.qualcomm.com>

Re: [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@oss.qualcomm.com> wrote:
>
> On Tue, Jul 28, 2026 at 5:24 PM Peixin Xie
> <peixin.xie@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@vger.kernel.org
> > Acked-by: Sudeep Holla <sudeep.holla@kernel.org>
> > Reviewed-by: Yixun Lan <dlan@kernel.org>
> > Signed-off-by: Peixin Xie <peixin.xie@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

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

[lihuisong (C)]

On 7/28/2026 7:47 PM, Peixin Xie 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@vger.kernel.org
> Acked-by: Sudeep Holla <sudeep.holla@kernel.org>
> Reviewed-by: Yixun Lan <dlan@kernel.org>
> Signed-off-by: Peixin Xie <peixin.xie@linux.spacemit.com>
> ---
LGTM,
Reviewed-by: Huisong Li <lihuisong@huawei.com>
>