From d1b4470b0b7e5f6944772dc70e65b69d8bab581f Mon Sep 17 00:00:00 2001 From: Ankur Arora Date: Wed, 25 Sep 2024 16:24:25 -0700 Subject: [PATCH] arm64: support cpuidle-haltpoll Add architectural support for the cpuidle-haltpoll driver by defining arch_haltpoll_*(). Also define ARCH_CPUIDLE_HALTPOLL to allow cpuidle-haltpoll to be selected. Haltpoll uses poll_idle() to do the actual polling. This in turn uses smp_cond_load*() to wait until there's a specific store to a cacheline. In the edge case -- no stores to the cacheline and no interrupt -- the event-stream provides the terminating condition ensuring we don't wait forever. But because the event-stream runs at a fixed frequency (configured at 10kHz) haltpoll might spend more time in the polling stage than specified by cpuidle_poll_time(). This would only happen in the last iteration, since overshooting the poll_limit means the governor will move out of the polling stage. Tested-by: Haris Okanovic Tested-by: Misono Tomohiro Signed-off-by: Ankur Arora Reviewed-by: Haris Okanovic --- arch/arm64/Kconfig | 6 ++++++ arch/arm64/include/asm/cpuidle_haltpoll.h | 24 +++++++++++++++++++++++ 2 files changed, 30 insertions(+) create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 43762c68e357..bd00647f6013 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -2428,6 +2428,12 @@ config ARCH_HIBERNATION_HEADER config ARCH_SUSPEND_POSSIBLE def_bool y +config ARCH_CPUIDLE_HALTPOLL + bool "Enable selection of the cpuidle-haltpoll driver" + help + cpuidle-haltpoll allows for adaptive polling based on + current load before entering the idle state. + endmenu # "Power management options" menu "CPU Power Management" diff --git a/arch/arm64/include/asm/cpuidle_haltpoll.h b/arch/arm64/include/asm/cpuidle_haltpoll.h new file mode 100644 index 000000000000..91f0be707629 --- /dev/null +++ b/arch/arm64/include/asm/cpuidle_haltpoll.h @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _ARCH_HALTPOLL_H +#define _ARCH_HALTPOLL_H + +static inline void arch_haltpoll_enable(unsigned int cpu) { } +static inline void arch_haltpoll_disable(unsigned int cpu) { } + +static inline bool arch_haltpoll_want(bool force) +{ + /* + * Enabling haltpoll requires two things: + * + * - Event stream support to provide a terminating condition to the + * WFE in the poll loop. + * + * - KVM support for arch_haltpoll_enable(), arch_haltpoll_disable(). + * + * Given that the second is missing, only allow force loading for + * haltpoll. + */ + return force; +} +#endif -- 2.47.3