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/types.h> 12 #include <linux/kernel.h> 13 #include <linux/signal.h> 14 #include <linux/sched.h> 15 #include <linux/init.h> 16 #include <linux/io.h> 17 #include <asm/thread_notify.h> 18 #include <asm/cputype.h> 19 20 asm(" .arch armv5te\n"); 21 22 static inline void dsp_save_state(u32 *state) 23 { 24 __asm__ __volatile__ ( 25 "mrrc p0, 0, %0, %1, c0\n" 26 : "=r" (state[0]), "=r" (state[1])); 27 } 28 29 static inline void dsp_load_state(u32 *state) 30 { 31 __asm__ __volatile__ ( 32 "mcrr p0, 0, %0, %1, c0\n" 33 : : "r" (state[0]), "r" (state[1])); 34 } 35 36 static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t) 37 { 38 struct thread_info *thread = t; 39 40 switch (cmd) { 41 case THREAD_NOTIFY_FLUSH: 42 thread->cpu_context.extra[0] = 0; 43 thread->cpu_context.extra[1] = 0; 44 break; 45 46 case THREAD_NOTIFY_SWITCH: 47 dsp_save_state(current_thread_info()->cpu_context.extra); 48 dsp_load_state(thread->cpu_context.extra); 49 break; 50 } 51 52 return NOTIFY_DONE; 53 } 54 55 static struct notifier_block dsp_notifier_block = { 56 .notifier_call = dsp_do, 57 }; 58 59 60 #ifdef CONFIG_IWMMXT 61 static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t) 62 { 63 struct thread_info *thread = t; 64 65 switch (cmd) { 66 case THREAD_NOTIFY_FLUSH: 67 /* 68 * flush_thread() zeroes thread->fpstate, so no need 69 * to do anything here. 70 * 71 * FALLTHROUGH: Ensure we don't try to overwrite our newly 72 * initialised state information on the first fault. 73 */ 74 75 case THREAD_NOTIFY_EXIT: 76 iwmmxt_task_release(thread); 77 break; 78 79 case THREAD_NOTIFY_SWITCH: 80 iwmmxt_task_switch(thread); 81 break; 82 } 83 84 return NOTIFY_DONE; 85 } 86 87 static struct notifier_block iwmmxt_notifier_block = { 88 .notifier_call = iwmmxt_do, 89 }; 90 #endif 91 92 93 static u32 __init xscale_cp_access_read(void) 94 { 95 u32 value; 96 97 __asm__ __volatile__ ( 98 "mrc p15, 0, %0, c15, c1, 0\n\t" 99 : "=r" (value)); 100 101 return value; 102 } 103 104 static void __init xscale_cp_access_write(u32 value) 105 { 106 u32 temp; 107 108 __asm__ __volatile__ ( 109 "mcr p15, 0, %1, c15, c1, 0\n\t" 110 "mrc p15, 0, %0, c15, c1, 0\n\t" 111 "mov %0, %0\n\t" 112 "sub pc, pc, #4\n\t" 113 : "=r" (temp) : "r" (value)); 114 } 115 116 /* 117 * Detect whether we have a MAC coprocessor (40 bit register) or an 118 * iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000 119 * into a coprocessor register and reading it back, and checking 120 * whether the upper word survived intact. 121 */ 122 static int __init cpu_has_iwmmxt(void) 123 { 124 u32 lo; 125 u32 hi; 126 127 /* 128 * This sequence is interpreted by the DSP coprocessor as: 129 * mar acc0, %2, %3 130 * mra %0, %1, acc0 131 * 132 * And by the iWMMXt coprocessor as: 133 * tmcrr wR0, %2, %3 134 * tmrrc %0, %1, wR0 135 */ 136 __asm__ __volatile__ ( 137 "mcrr p0, 0, %2, %3, c0\n" 138 "mrrc p0, 0, %0, %1, c0\n" 139 : "=r" (lo), "=r" (hi) 140 : "r" (0), "r" (0x100)); 141 142 return !!hi; 143 } 144 145 146 /* 147 * If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we 148 * disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy 149 * switch code handle iWMMXt context switching. If on the other 150 * hand the CPU has a DSP coprocessor, we keep access to CP0 enabled 151 * all the time, and save/restore acc0 on context switch in non-lazy 152 * fashion. 153 */ 154 static int __init xscale_cp0_init(void) 155 { 156 u32 cp_access; 157 158 /* do not attempt to probe iwmmxt on non-xscale family CPUs */ 159 if (!cpu_is_xscale_family()) 160 return 0; 161 162 cp_access = xscale_cp_access_read() & ~3; 163 xscale_cp_access_write(cp_access | 1); 164 165 if (cpu_has_iwmmxt()) { 166 #ifndef CONFIG_IWMMXT 167 pr_warn("CAUTION: XScale iWMMXt coprocessor detected, but kernel support is missing.\n"); 168 #else 169 pr_info("XScale iWMMXt coprocessor detected.\n"); 170 elf_hwcap |= HWCAP_IWMMXT; 171 thread_register_notifier(&iwmmxt_notifier_block); 172 #endif 173 } else { 174 pr_info("XScale DSP coprocessor detected.\n"); 175 thread_register_notifier(&dsp_notifier_block); 176 cp_access |= 1; 177 } 178 179 xscale_cp_access_write(cp_access); 180 181 return 0; 182 } 183 184 late_initcall(xscale_cp0_init); 185