diff --git a/MAINTAINERS b/MAINTAINERS index 4a8b0fd665ce..0877031e6b34 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6851,6 +6851,13 @@ L: linux-riscv@lists.infradead.org S: Maintained F: drivers/cpuidle/cpuidle-riscv-sbi.c +CPUIDLE DRIVER - S390 +M: Mete Durlu +L: linux-pm@vger.kernel.org +L: linux-s390@vger.kernel.org +S: Maintained +F: drivers/cpuidle/cpuidle-s390.c + CPUMASK API [RUST] M: Viresh Kumar R: Yury Norov @@ -23790,6 +23797,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git F: Documentation/driver-api/s390-drivers.rst F: Documentation/arch/s390/ F: arch/s390/ +F: drivers/cpuidle/cpuidle-s390.c F: drivers/s390/ F: drivers/watchdog/diag288_wdt.c diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 84404e6778d5..3b9d352cadef 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -20,6 +20,9 @@ config ARCH_HAS_ILOG2_U64 config ARCH_PROC_KCORE_TEXT def_bool y +config ARCH_HAS_CPU_RELAX + def_bool y + config GENERIC_HWEIGHT def_bool !HAVE_MARCH_Z196_FEATURES @@ -705,6 +708,8 @@ config KERNEL_IMAGE_BASE endmenu +source "drivers/cpuidle/Kconfig" + menu "Memory setup" config ARCH_SPARSEMEM_ENABLE diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig index d6d8386d3f02..00e2562041fd 100644 --- a/drivers/cpuidle/Kconfig +++ b/drivers/cpuidle/Kconfig @@ -71,6 +71,11 @@ depends on RISCV source "drivers/cpuidle/Kconfig.riscv" endmenu +menu "S390 CPU Idle Drivers" +depends on S390 +source "drivers/cpuidle/Kconfig.s390" +endmenu + config HALTPOLL_CPUIDLE tristate "Halt poll cpuidle driver" depends on X86 && KVM_GUEST diff --git a/drivers/cpuidle/Kconfig.s390 b/drivers/cpuidle/Kconfig.s390 new file mode 100644 index 000000000000..c9acf7ba8eee --- /dev/null +++ b/drivers/cpuidle/Kconfig.s390 @@ -0,0 +1,11 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# S390 CPU Idle drivers +# + +config S390_CPUIDLE + bool "S390 CPU idle driver" + default y + help + Select this option to enable processor idle state management + through cpuidle subsystem. diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile index 1de9e92c5b0f..88cbc2a7aea8 100644 --- a/drivers/cpuidle/Makefile +++ b/drivers/cpuidle/Makefile @@ -42,3 +42,7 @@ obj-$(CONFIG_POWERNV_CPUIDLE) += cpuidle-powernv.o ############################################################################### # RISC-V drivers obj-$(CONFIG_RISCV_SBI_CPUIDLE) += cpuidle-riscv-sbi.o + +############################################################################### +# S390 drivers +obj-$(CONFIG_S390_CPUIDLE) += cpuidle-s390.o diff --git a/drivers/cpuidle/cpuidle-s390.c b/drivers/cpuidle/cpuidle-s390.c new file mode 100644 index 000000000000..1d02a77ebce0 --- /dev/null +++ b/drivers/cpuidle/cpuidle-s390.c @@ -0,0 +1,115 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * s390 generic CPU idle driver. + * + * Copyright IBM Corp. 2026 + */ + +#define pr_fmt(fmt) "CPUidle s390: " fmt + +#include +#include +#include +#include + +static __cpuidle int s390_enter_idle(struct cpuidle_device *dev, + struct cpuidle_driver *drv, + int index) +{ + arch_cpu_idle(); + return index; +} + +static struct cpuidle_driver s390_cpuidle_driver = { + .cpumask = (struct cpumask *)cpu_present_mask, + .name = "s390-idle", + .states = { + { /* entry 0 is for polling */}, + { + .enter = s390_enter_idle, + .name = "IDLE", + .desc = "ENABLED WAIT", + }, + }, + .safe_state_index = 0, + .state_count = 2, +}; + +static int s390_cpuidle_cpu_online(unsigned int cpu) +{ + struct cpuidle_device *dev = &per_cpu(cpuidle_dev, cpu); + int rc; + + if (dev->registered) { + cpuidle_pause_and_lock(); + rc = cpuidle_enable_device(dev); + cpuidle_resume_and_unlock(); + if (rc) + pr_err("Failed to enable cpuidle device on cpu %u\n", cpu); + } else { + dev->cpu = cpu; + rc = cpuidle_register_device(dev); + if (rc) + pr_err("Failed to register cpuidle driver on cpu %u\n", cpu); + } + return rc; +} + +static int s390_cpuidle_cpu_dead(unsigned int cpu) +{ + struct cpuidle_device *dev = &per_cpu(cpuidle_dev, cpu); + + if (!dev->registered) + return 0; + cpuidle_pause_and_lock(); + cpuidle_disable_device(dev); + cpuidle_resume_and_unlock(); + return 0; +} + +/* + * The target_residency and exit_latency values are benchmark-derived estimates + * that remain non-deterministic due to s390's virtualized architecture. + * + * Configuration strategy: + * - Poll idle state: Values derived from the next enabled idle state (EW) + * - Enabled Wait state: Values selected based on idle behavior and empirical + * measurement data + * + * Goal is to improve responsiveness for workloads with frequent sleep/wakeup + * cycles while minimizing any side effects. + */ +static void __init s390_cpuidle_ew_tune(void) +{ + struct cpuidle_state *state = &s390_cpuidle_driver.states[1]; + + if (machine_is_lpar()) { + state->target_residency = 5; + state->exit_latency = 5; + } else { + state->target_residency = 1; + state->exit_latency = 1; + } +} + +static int __init s390_cpuidle_init(void) +{ + int rc; + + s390_cpuidle_ew_tune(); + cpuidle_poll_state_init(&s390_cpuidle_driver); + rc = cpuidle_register(&s390_cpuidle_driver, NULL); + if (rc) + return rc; + rc = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "cpuidle/s390:online", + s390_cpuidle_cpu_online, + s390_cpuidle_cpu_dead); + if (rc < 0) { + cpuidle_unregister(&s390_cpuidle_driver); + pr_err("Failed to allocate hotplug state: cpuidle/s390:online\n"); + return rc; + } + return 0; +} +device_initcall(s390_cpuidle_init);