1 /* 2 * linux/arch/arm/mach-spear13xx/hotplug.c 3 * 4 * Copyright (C) 2012 ST Microelectronics Ltd. 5 * Deepak Sikri <deepak.sikri@st.com> 6 * 7 * based upon linux/arch/arm/mach-realview/hotplug.c 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License version 2 as 11 * published by the Free Software Foundation. 12 */ 13 #include <linux/kernel.h> 14 #include <linux/errno.h> 15 #include <linux/smp.h> 16 #include <asm/cp15.h> 17 #include <asm/smp_plat.h> 18 19 #include "generic.h" 20 21 static inline void cpu_enter_lowpower(void) 22 { 23 unsigned int v; 24 25 asm volatile( 26 " mcr p15, 0, %1, c7, c5, 0\n" 27 " dsb\n" 28 /* 29 * Turn off coherency 30 */ 31 " mrc p15, 0, %0, c1, c0, 1\n" 32 " bic %0, %0, #0x20\n" 33 " mcr p15, 0, %0, c1, c0, 1\n" 34 " mrc p15, 0, %0, c1, c0, 0\n" 35 " bic %0, %0, %2\n" 36 " mcr p15, 0, %0, c1, c0, 0\n" 37 : "=&r" (v) 38 : "r" (0), "Ir" (CR_C) 39 : "cc", "memory"); 40 } 41 42 static inline void cpu_leave_lowpower(void) 43 { 44 unsigned int v; 45 46 asm volatile("mrc p15, 0, %0, c1, c0, 0\n" 47 " orr %0, %0, %1\n" 48 " mcr p15, 0, %0, c1, c0, 0\n" 49 " mrc p15, 0, %0, c1, c0, 1\n" 50 " orr %0, %0, #0x20\n" 51 " mcr p15, 0, %0, c1, c0, 1\n" 52 : "=&r" (v) 53 : "Ir" (CR_C) 54 : "cc"); 55 } 56 57 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious) 58 { 59 for (;;) { 60 wfi(); 61 62 if (spear_pen_release == cpu) { 63 /* 64 * OK, proper wakeup, we're done 65 */ 66 break; 67 } 68 69 /* 70 * Getting here, means that we have come out of WFI without 71 * having been woken up - this shouldn't happen 72 * 73 * Just note it happening - when we're woken, we can report 74 * its occurrence. 75 */ 76 (*spurious)++; 77 } 78 } 79 80 /* 81 * platform-specific code to shutdown a CPU 82 * 83 * Called with IRQs disabled 84 */ 85 void spear13xx_cpu_die(unsigned int cpu) 86 { 87 int spurious = 0; 88 89 /* 90 * we're ready for shutdown now, so do it 91 */ 92 cpu_enter_lowpower(); 93 spear13xx_do_lowpower(cpu, &spurious); 94 95 /* 96 * bring this CPU back into the world of cache 97 * coherency, and then restore interrupts 98 */ 99 cpu_leave_lowpower(); 100 101 if (spurious) 102 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious); 103 } 104