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 */
 15static int (*olpc_ofw_cif)(int *);
 16
 17/* page dir entry containing OFW's pgdir table; filled in by head_32.S */
 18u32 olpc_ofw_pgd __initdata;
 19
 20static DEFINE_SPINLOCK(ofw_lock);
 21
 22#define MAXARGS 10
 23
 24void __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
 47int __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}
 79EXPORT_SYMBOL_GPL(__olpc_ofw);
 80
 81bool olpc_ofw_present(void)
 82{
 83	return olpc_ofw_cif != NULL;
 84}
 85EXPORT_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
 93void __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
118bool __init olpc_ofw_is_installed(void)
119{
120	return olpc_ofw_cif != NULL;
121}