arch/arm/kernel/pj4-cp0.c

   1 /*
   2  * linux/arch/arm/kernel/pj4-cp0.c
   3  *
   4  * PJ4 iWMMXt coprocessor context switching and handling
   5  *
   6  * Copyright (c) 2010 Marvell International Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/signal.h>
  16 #include <linux/sched.h>
  17 #include <linux/init.h>
  18 #include <linux/io.h>
  19 #include <asm/thread_notify.h>
  20 #include <asm/cputype.h>
  21
  22 static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
  23 {
  24         struct thread_info *thread = t;
  25
  26         switch (cmd) {
  27         case THREAD_NOTIFY_FLUSH:
  28                 /*
  29                  * flush_thread() zeroes thread->fpstate, so no need
  30                  * to do anything here.
  31                  *
  32                  * FALLTHROUGH: Ensure we don't try to overwrite our newly
  33                  * initialised state information on the first fault.
  34                  */
  35
  36         case THREAD_NOTIFY_EXIT:
  37                 iwmmxt_task_release(thread);
  38                 break;
  39
  40         case THREAD_NOTIFY_SWITCH:
  41                 iwmmxt_task_switch(thread);
  42                 break;
  43         }
  44
  45         return NOTIFY_DONE;
  46 }
  47
  48 static struct notifier_block __maybe_unused iwmmxt_notifier_block = {
  49         .notifier_call  = iwmmxt_do,
  50 };
  51
  52
  53 static u32 __init pj4_cp_access_read(void)
  54 {
  55         u32 value;
  56
  57         __asm__ __volatile__ (
  58                 "mrc    p15, 0, %0, c1, c0, 2\n\t"
  59                 : "=r" (value));
  60         return value;
  61 }
  62
  63 static void __init pj4_cp_access_write(u32 value)
  64 {
  65         u32 temp;
  66
  67         __asm__ __volatile__ (
  68                 "mcr    p15, 0, %1, c1, c0, 2\n\t"
  69                 "mrc    p15, 0, %0, c1, c0, 2\n\t"
  70                 "mov    %0, %0\n\t"
  71                 "sub    pc, pc, #4\n\t"
  72                 : "=r" (temp) : "r" (value));
  73 }
  74
  75 static int __init pj4_get_iwmmxt_version(void)
  76 {
  77         u32 cp_access, wcid;
  78
  79         cp_access = pj4_cp_access_read();
  80         pj4_cp_access_write(cp_access | 0xf);
  81
  82         /* check if coprocessor 0 and 1 are available */
  83         if ((pj4_cp_access_read() & 0xf) != 0xf) {
  84                 pj4_cp_access_write(cp_access);
  85                 return -ENODEV;
  86         }
  87
  88         /* read iWMMXt coprocessor id register p1, c0 */
  89         __asm__ __volatile__ ("mrc    p1, 0, %0, c0, c0, 0\n" : "=r" (wcid));
  90
  91         pj4_cp_access_write(cp_access);
  92
  93         /* iWMMXt v1 */
  94         if ((wcid & 0xffffff00) == 0x56051000)
  95                 return 1;
  96         /* iWMMXt v2 */
  97         if ((wcid & 0xffffff00) == 0x56052000)
  98                 return 2;
  99
 100         return -EINVAL;
 101 }
 102
 103 /*
 104  * Disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
 105  * switch code handle iWMMXt context switching.
 106  */
 107 static int __init pj4_cp0_init(void)
 108 {
 109         u32 __maybe_unused cp_access;
 110         int vers;
 111
 112         if (!cpu_is_pj4())
 113                 return 0;
 114
 115         vers = pj4_get_iwmmxt_version();
 116         if (vers < 0)
 117                 return 0;
 118
 119 #ifndef CONFIG_IWMMXT
 120         pr_info("PJ4 iWMMXt coprocessor detected, but kernel support is missing.\n");
 121 #else
 122         cp_access = pj4_cp_access_read() & ~0xf;
 123         pj4_cp_access_write(cp_access);
 124
 125         pr_info("PJ4 iWMMXt v%d coprocessor enabled.\n", vers);
 126         elf_hwcap |= HWCAP_IWMMXT;
 127         thread_register_notifier(&iwmmxt_notifier_block);
 128 #endif
 129
 130         return 0;
 131 }
 132
 133 late_initcall(pj4_cp0_init);