-----Original Message-----
From: Will Deacon <will@xxxxxxxxxx>
Sent: Thursday, September 14, 2023 6:22 AM
To: Pawandeep Oza (QUIC) <quic_poza@xxxxxxxxxxx>
Cc: sudeep.holla@xxxxxxx; catalin.marinas@xxxxxxx; rafael@xxxxxxxxxx; lenb@xxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v5] cpuidle, ACPI: Evaluate LPI arch_flags for broadcast timer
On Tue, Sep 12, 2023 at 10:29:33AM -0700, Oza Pawandeep wrote:
> Arm(r) Functional Fixed Hardware Specification defines LPI states, which
> provide an architectural context loss flags field that can be used to
> describe the context that might be lost when an LPI state is entered.
>
> - Core context Lost
> - General purpose registers.
> - Floating point and SIMD registers.
> - System registers, include the System register based
> - generic timer for the core.
> - Debug register in the core power domain.
> - PMU registers in the core power domain.
> - Trace register in the core power domain.
> - Trace context loss
> - GICR
> - GICD
>
> Qualcomm's custom CPUs preserves the architectural state, including
> keeping the power domain for local timers active.
> when core is power gated, the local timers are sufficient to wake the
> core up without needing broadcast timer.
>
> The patch fixes the evaluation of cpuidle arch_flags, and moves only
> to broadcast timer if core context lost is defined in ACPI LPI.
>
> Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> Signed-off-by: Oza Pawandeep <quic_poza@xxxxxxxxxxx>
>
> diff --git a/arch/arm64/include/asm/acpi.h
> b/arch/arm64/include/asm/acpi.h index 4d537d56eb84..a30b6e16628d
> 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -9,6 +9,7 @@
> #ifndef _ASM_ACPI_H
> #define _ASM_ACPI_H
>
> +#include <linux/cpuidle.h>
> #include <linux/efi.h>
> #include <linux/memblock.h>
> #include <linux/psci.h>
> @@ -44,6 +45,25 @@
>
> #define ACPI_MADT_GICC_TRBE (offsetof(struct acpi_madt_generic_interrupt, \
> trbe_interrupt) + sizeof(u16))
> +/*
> + * Arm(r) Functional Fixed Hardware Specification Version 1.2.
> + * Table 2: Arm Architecture context loss flags */
> +#define CPUIDLE_CORE_CTXT BIT(0) /* Core context Lost */
> +
> +#ifndef arch_update_idle_state_flags
> +static __always_inline void _arch_update_idle_state_flags(u32 arch_flags,
> + unsigned int *sflags)
> +{
> + if (arch_flags & CPUIDLE_CORE_CTXT)
> + *sflags |= CPUIDLE_FLAG_TIMER_STOP; } #define
> +arch_update_idle_state_flags _arch_update_idle_state_flags #endif
Why do you need the #ifndef/endif guards here? I'd have thought you'd _always_ want this definition to be the one used, with the compiler complaining otherwise.
Oza: thanks, Will!, will remove it.
Will
