1 /* 2 * linux/arch/arm/kernel/xscale-cp0.c 3 * 4 * XScale DSP and iWMMXt coprocessor context switching and handling 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <linux/module.h> 12 #include <linux/types.h> 13 #include <linux/kernel.h> 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/init.h> 17 #include <linux/io.h> 18 #include <asm/thread_notify.h> 19 20 static inline void dsp_save_state(u32 *state) 21 { 22 __asm__ __volatile__ ( 23 "mrrc p0, 0, %0, %1, c0\n" 24 : "=r" (state[0]), "=r" (state[1])); 25 } 26 27 static inline void dsp_load_state(u32 *state) 28 { 29 __asm__ __volatile__ ( 30 "mcrr p0, 0, %0, %1, c0\n" 31 : : "r" (state[0]), "r" (state[1])); 32 } 33 34 static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t) 35 { 36 struct thread_info *thread = t; 37 38 switch (cmd) { 39 case THREAD_NOTIFY_FLUSH: 40 thread->cpu_context.extra[0] = 0; 41 thread->cpu_context.extra[1] = 0; 42 break; 43 44 case THREAD_NOTIFY_SWITCH: 45 dsp_save_state(current_thread_info()->cpu_context.extra); 46 dsp_load_state(thread->cpu_context.extra); 47 break; 48 } 49 50 return NOTIFY_DONE; 51 } 52 53 static struct notifier_block dsp_notifier_block = { 54 .notifier_call = dsp_do, 55 }; 56 57 58 #ifdef CONFIG_IWMMXT 59 static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t) 60 { 61 struct thread_info *thread = t; 62 63 switch (cmd) { 64 case THREAD_NOTIFY_FLUSH: 65 /* 66 * flush_thread() zeroes thread->fpstate, so no need 67 * to do anything here. 68 * 69 * FALLTHROUGH: Ensure we don't try to overwrite our newly 70 * initialised state information on the first fault. 71 */ 72 73 case THREAD_NOTIFY_EXIT: 74 iwmmxt_task_release(thread); 75 break; 76 77 case THREAD_NOTIFY_SWITCH: 78 iwmmxt_task_switch(thread); 79 break; 80 } 81 82 return NOTIFY_DONE; 83 } 84 85 static struct notifier_block iwmmxt_notifier_block = { 86 .notifier_call = iwmmxt_do, 87 }; 88 #endif 89 90 91 static u32 __init xscale_cp_access_read(void) 92 { 93 u32 value; 94 95 __asm__ __volatile__ ( 96 "mrc p15, 0, %0, c15, c1, 0\n\t" 97 : "=r" (value)); 98 99 return value; 100 } 101 102 static void __init xscale_cp_access_write(u32 value) 103 { 104 u32 temp; 105 106 __asm__ __volatile__ ( 107 "mcr p15, 0, %1, c15, c1, 0\n\t" 108 "mrc p15, 0, %0, c15, c1, 0\n\t" 109 "mov %0, %0\n\t" 110 "sub pc, pc, #4\n\t" 111 : "=r" (temp) : "r" (value)); 112 } 113 114 /* 115 * Detect whether we have a MAC coprocessor (40 bit register) or an 116 * iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000 117 * into a coprocessor register and reading it back, and checking 118 * whether the upper word survived intact. 119 */ 120 static int __init cpu_has_iwmmxt(void) 121 { 122 u32 lo; 123 u32 hi; 124 125 /* 126 * This sequence is interpreted by the DSP coprocessor as: 127 * mar acc0, %2, %3 128 * mra %0, %1, acc0 129 * 130 * And by the iWMMXt coprocessor as: 131 * tmcrr wR0, %2, %3 132 * tmrrc %0, %1, wR0 133 */ 134 __asm__ __volatile__ ( 135 "mcrr p0, 0, %2, %3, c0\n" 136 "mrrc p0, 0, %0, %1, c0\n" 137 : "=r" (lo), "=r" (hi) 138 : "r" (0), "r" (0x100)); 139 140 return !!hi; 141 } 142 143 144 /* 145 * If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we 146 * disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy 147 * switch code handle iWMMXt context switching. If on the other 148 * hand the CPU has a DSP coprocessor, we keep access to CP0 enabled 149 * all the time, and save/restore acc0 on context switch in non-lazy 150 * fashion. 151 */ 152 static int __init xscale_cp0_init(void) 153 { 154 u32 cp_access; 155 156 cp_access = xscale_cp_access_read() & ~3; 157 xscale_cp_access_write(cp_access | 1); 158 159 if (cpu_has_iwmmxt()) { 160 #ifndef CONFIG_IWMMXT 161 printk(KERN_WARNING "CAUTION: XScale iWMMXt coprocessor " 162 "detected, but kernel support is missing.\n"); 163 #else 164 printk(KERN_INFO "XScale iWMMXt coprocessor detected.\n"); 165 elf_hwcap |= HWCAP_IWMMXT; 166 thread_register_notifier(&iwmmxt_notifier_block); 167 #endif 168 } else { 169 printk(KERN_INFO "XScale DSP coprocessor detected.\n"); 170 thread_register_notifier(&dsp_notifier_block); 171 cp_access |= 1; 172 } 173 174 xscale_cp_access_write(cp_access); 175 176 return 0; 177 } 178 179 late_initcall(xscale_cp0_init); 180