1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/arch/arm/mach-spear13xx/hotplug.c 4 * 5 * Copyright (C) 2012 ST Microelectronics Ltd. 6 * Deepak Sikri <deepak.sikri@st.com> 7 * 8 * based upon linux/arch/arm/mach-realview/hotplug.c 9 */ 10 #include <linux/kernel.h> 11 #include <linux/errno.h> 12 #include <linux/smp.h> 13 #include <asm/cp15.h> 14 #include <asm/smp_plat.h> 15 16 #include "generic.h" 17 18 static inline void cpu_enter_lowpower(void) 19 { 20 unsigned int v; 21 22 asm volatile( 23 " mcr p15, 0, %1, c7, c5, 0\n" 24 " dsb\n" 25 /* 26 * Turn off coherency 27 */ 28 " mrc p15, 0, %0, c1, c0, 1\n" 29 " bic %0, %0, #0x20\n" 30 " mcr p15, 0, %0, c1, c0, 1\n" 31 " mrc p15, 0, %0, c1, c0, 0\n" 32 " bic %0, %0, %2\n" 33 " mcr p15, 0, %0, c1, c0, 0\n" 34 : "=&r" (v) 35 : "r" (0), "Ir" (CR_C) 36 : "cc", "memory"); 37 } 38 39 static inline void cpu_leave_lowpower(void) 40 { 41 unsigned int v; 42 43 asm volatile("mrc p15, 0, %0, c1, c0, 0\n" 44 " orr %0, %0, %1\n" 45 " mcr p15, 0, %0, c1, c0, 0\n" 46 " mrc p15, 0, %0, c1, c0, 1\n" 47 " orr %0, %0, #0x20\n" 48 " mcr p15, 0, %0, c1, c0, 1\n" 49 : "=&r" (v) 50 : "Ir" (CR_C) 51 : "cc"); 52 } 53 54 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious) 55 { 56 for (;;) { 57 wfi(); 58 59 if (spear_pen_release == cpu) { 60 /* 61 * OK, proper wakeup, we're done 62 */ 63 break; 64 } 65 66 /* 67 * Getting here, means that we have come out of WFI without 68 * having been woken up - this shouldn't happen 69 * 70 * Just note it happening - when we're woken, we can report 71 * its occurrence. 72 */ 73 (*spurious)++; 74 } 75 } 76 77 /* 78 * platform-specific code to shutdown a CPU 79 * 80 * Called with IRQs disabled 81 */ 82 void spear13xx_cpu_die(unsigned int cpu) 83 { 84 int spurious = 0; 85 86 /* 87 * we're ready for shutdown now, so do it 88 */ 89 cpu_enter_lowpower(); 90 spear13xx_do_lowpower(cpu, &spurious); 91 92 /* 93 * bring this CPU back into the world of cache 94 * coherency, and then restore interrupts 95 */ 96 cpu_leave_lowpower(); 97 98 if (spurious) 99 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious); 100 } 101