arch/x86/platform/olpc/olpc_ofw.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/kernel.h>
   3 #include <linux/export.h>
   4 #include <linux/spinlock_types.h>
   5 #include <linux/init.h>
   6 #include <linux/pgtable.h>
   7 #include <asm/page.h>
   8 #include <asm/setup.h>
   9 #include <asm/io.h>
  10 #include <asm/cpufeature.h>
  11 #include <asm/special_insns.h>
  12 #include <asm/olpc_ofw.h>
  13
  14 /* address of OFW callback interface; will be NULL if OFW isn't found */
  15 static int (*olpc_ofw_cif)(int *);
  16
  17 /* page dir entry containing OFW's pgdir table; filled in by head_32.S */
  18 u32 olpc_ofw_pgd __initdata;
  19
  20 static DEFINE_SPINLOCK(ofw_lock);
  21
  22 #define MAXARGS 10
  23
  24 void __init setup_olpc_ofw_pgd(void)
  25 {
  26         pgd_t *base, *ofw_pde;
  27
  28         if (!olpc_ofw_cif)
  29                 return;
  30
  31         /* fetch OFW's PDE */
  32         base = early_ioremap(olpc_ofw_pgd, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
  33         if (!base) {
  34                 printk(KERN_ERR "failed to remap OFW's pgd - disabling OFW!\n");
  35                 olpc_ofw_cif = NULL;
  36                 return;
  37         }
  38         ofw_pde = &base[OLPC_OFW_PDE_NR];
  39
  40         /* install OFW's PDE permanently into the kernel's pgtable */
  41         set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde);
  42         /* implicit optimization barrier here due to uninline function return */
  43
  44         early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
  45 }
  46
  47 int __olpc_ofw(const char *name, int nr_args, const void **args, int nr_res,
  48                 void **res)
  49 {
  50         int ofw_args[MAXARGS + 3];
  51         unsigned long flags;
  52         int ret, i, *p;
  53
  54         BUG_ON(nr_args + nr_res > MAXARGS);
  55
  56         if (!olpc_ofw_cif)
  57                 return -EIO;
  58
  59         ofw_args[0] = (int)name;
  60         ofw_args[1] = nr_args;
  61         ofw_args[2] = nr_res;
  62
  63         p = &ofw_args[3];
  64         for (i = 0; i < nr_args; i++, p++)
  65                 *p = (int)args[i];
  66
  67         /* call into ofw */
  68         spin_lock_irqsave(&ofw_lock, flags);
  69         ret = olpc_ofw_cif(ofw_args);
  70         spin_unlock_irqrestore(&ofw_lock, flags);
  71
  72         if (!ret) {
  73                 for (i = 0; i < nr_res; i++, p++)
  74                         *((int *)res[i]) = *p;
  75         }
  76
  77         return ret;
  78 }
  79 EXPORT_SYMBOL_GPL(__olpc_ofw);
  80
  81 bool olpc_ofw_present(void)
  82 {
  83         return olpc_ofw_cif != NULL;
  84 }
  85 EXPORT_SYMBOL_GPL(olpc_ofw_present);
  86
  87 /* OFW cif _should_ be above this address */
  88 #define OFW_MIN 0xff000000
  89
  90 /* OFW starts on a 1MB boundary */
  91 #define OFW_BOUND (1<<20)
  92
  93 void __init olpc_ofw_detect(void)
  94 {
  95         struct olpc_ofw_header *hdr = &boot_params.olpc_ofw_header;
  96         unsigned long start;
  97
  98         /* ensure OFW booted us by checking for "OFW " string */
  99         if (hdr->ofw_magic != OLPC_OFW_SIG)
 100                 return;
 101
 102         olpc_ofw_cif = (int (*)(int *))hdr->cif_handler;
 103
 104         if ((unsigned long)olpc_ofw_cif < OFW_MIN) {
 105                 printk(KERN_ERR "OFW detected, but cif has invalid address 0x%lx - disabling.\n",
 106                                 (unsigned long)olpc_ofw_cif);
 107                 olpc_ofw_cif = NULL;
 108                 return;
 109         }
 110
 111         /* determine where OFW starts in memory */
 112         start = round_down((unsigned long)olpc_ofw_cif, OFW_BOUND);
 113         printk(KERN_INFO "OFW detected in memory, cif @ 0x%lx (reserving top %ldMB)\n",
 114                         (unsigned long)olpc_ofw_cif, (-start) >> 20);
 115         reserve_top_address(-start);
 116 }
 117
 118 bool __init olpc_ofw_is_installed(void)
 119 {
 120         return olpc_ofw_cif != NULL;
 121 }