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 static inline void cpu_enter_lowpower(void) 20 { 21 unsigned int v; 22 23 asm volatile( 24 " mcr p15, 0, %1, c7, c5, 0\n" 25 " dsb\n" 26 /* 27 * Turn off coherency 28 */ 29 " mrc p15, 0, %0, c1, c0, 1\n" 30 " bic %0, %0, #0x20\n" 31 " mcr p15, 0, %0, c1, c0, 1\n" 32 " mrc p15, 0, %0, c1, c0, 0\n" 33 " bic %0, %0, %2\n" 34 " mcr p15, 0, %0, c1, c0, 0\n" 35 : "=&r" (v) 36 : "r" (0), "Ir" (CR_C) 37 : "cc", "memory"); 38 } 39 40 static inline void cpu_leave_lowpower(void) 41 { 42 unsigned int v; 43 44 asm volatile("mrc p15, 0, %0, c1, c0, 0\n" 45 " orr %0, %0, %1\n" 46 " mcr p15, 0, %0, c1, c0, 0\n" 47 " mrc p15, 0, %0, c1, c0, 1\n" 48 " orr %0, %0, #0x20\n" 49 " mcr p15, 0, %0, c1, c0, 1\n" 50 : "=&r" (v) 51 : "Ir" (CR_C) 52 : "cc"); 53 } 54 55 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious) 56 { 57 for (;;) { 58 wfi(); 59 60 if (pen_release == cpu) { 61 /* 62 * OK, proper wakeup, we're done 63 */ 64 break; 65 } 66 67 /* 68 * Getting here, means that we have come out of WFI without 69 * having been woken up - this shouldn't happen 70 * 71 * Just note it happening - when we're woken, we can report 72 * its occurrence. 73 */ 74 (*spurious)++; 75 } 76 } 77 78 /* 79 * platform-specific code to shutdown a CPU 80 * 81 * Called with IRQs disabled 82 */ 83 void spear13xx_cpu_die(unsigned int cpu) 84 { 85 int spurious = 0; 86 87 /* 88 * we're ready for shutdown now, so do it 89 */ 90 cpu_enter_lowpower(); 91 spear13xx_do_lowpower(cpu, &spurious); 92 93 /* 94 * bring this CPU back into the world of cache 95 * coherency, and then restore interrupts 96 */ 97 cpu_leave_lowpower(); 98 99 if (spurious) 100 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious); 101 } 102