1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Low-level idle sequences 4 */ 5 6 #include <linux/cpu.h> 7 #include <linux/irqflags.h> 8 9 #include <asm/barrier.h> 10 #include <asm/cpuidle.h> 11 #include <asm/cpufeature.h> 12 #include <asm/sysreg.h> 13 14 enum { 15 ARM64_IDLE_WFI, 16 ARM64_IDLE_YIELD, 17 ARM64_IDLE_NOP, 18 } idle = ARM64_IDLE_WFI; 19 20 static int __init setup_idle(char *arg) 21 { 22 if (!arg) 23 return -1; 24 else if (!strcmp(arg, "wfi")) 25 idle = ARM64_IDLE_WFI; 26 else if (!strcmp(arg, "yield")) 27 idle = ARM64_IDLE_YIELD; 28 else if (!strcmp(arg, "nop")) 29 idle = ARM64_IDLE_NOP; 30 else 31 return -1; 32 33 return 0; 34 } 35 early_param("idle", setup_idle); 36 37 /* 38 * cpu_do_idle() 39 * 40 * Idle the processor (wait for interrupt). 41 * 42 * If the CPU supports priority masking we must do additional work to 43 * ensure that interrupts are not masked at the PMR (because the core will 44 * not wake up if we block the wake up signal in the interrupt controller). 45 */ 46 void __cpuidle cpu_do_idle(void) 47 { 48 struct arm_cpuidle_irq_context context; 49 50 arm_cpuidle_save_irq_context(&context); 51 52 if (likely(idle == ARM64_IDLE_WFI)) { 53 dsb(sy); 54 wfi(); 55 } else if (idle == ARM64_IDLE_YIELD) { 56 dsb(sy); 57 asm volatile("yield" ::: "memory"); 58 } 59 60 arm_cpuidle_restore_irq_context(&context); 61 } 62 63 /* 64 * This is our default idle handler. 65 */ 66 void __cpuidle arch_cpu_idle(void) 67 { 68 /* 69 * This should do all the clock switching and wait for interrupt 70 * tricks 71 */ 72 cpu_do_idle(); 73 } 74