x86, olpc: Add support for calling into OpenFirmware

Add support for saving OFW's cif, and later calling into it to run OFW
commands.  OFW remains resident in memory, living within virtual range
0xff800000 - 0xffc00000.  A single page directory entry points to the
pgdir that OFW actually uses, so rather than saving the entire page
table, we grab and install that one entry permanently in the kernel's
page table.

This is currently only used by the OLPC XO.  Note that this particular
calling convention breaks PAE and PAT, and so cannot be used on newer
x86 hardware.

Signed-off-by: Andres Salomon <dilinger@queued.net>
LKML-Reference: <20100618174653.7755a39a@dev.queued.net>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/arch/x86/kernel/olpc_ofw.c b/arch/x86/kernel/olpc_ofw.c
new file mode 100644
index 000000000000..469ee4384295
--- /dev/null
+++ b/arch/x86/kernel/olpc_ofw.c
@@ -0,0 +1,104 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <asm/page.h>
+#include <asm/setup.h>
+#include <asm/io.h>
+#include <asm/pgtable.h>
+#include <asm/olpc_ofw.h>
+
+/* address of OFW callback interface; will be NULL if OFW isn't found */
+static int (*olpc_ofw_cif)(int *);
+
+/* page dir entry containing OFW's pgdir table; filled in by head_32.S */
+u32 olpc_ofw_pgd __initdata;
+
+static DEFINE_SPINLOCK(ofw_lock);
+
+#define MAXARGS 10
+
+void __init setup_olpc_ofw_pgd(void)
+{
+	pgd_t *base, *ofw_pde;
+
+	if (!olpc_ofw_cif)
+		return;
+
+	/* fetch OFW's PDE */
+	base = early_ioremap(olpc_ofw_pgd, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
+	if (!base) {
+		printk(KERN_ERR "failed to remap OFW's pgd - disabling OFW!\n");
+		olpc_ofw_cif = NULL;
+		return;
+	}
+	ofw_pde = &base[OLPC_OFW_PDE_NR];
+
+	/* install OFW's PDE permanently into the kernel's pgtable */
+	set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde);
+	early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
+}
+
+int __olpc_ofw(const char *name, int nr_args, void **args, int nr_res,
+		void **res)
+{
+	int ofw_args[MAXARGS + 3];
+	unsigned long flags;
+	int ret, i, *p;
+
+	BUG_ON(nr_args + nr_res > MAXARGS);
+
+	if (!olpc_ofw_cif)
+		return -EIO;
+
+	ofw_args[0] = (int)name;
+	ofw_args[1] = nr_args;
+	ofw_args[2] = nr_res;
+
+	p = &ofw_args[3];
+	for (i = 0; i < nr_args; i++, p++)
+		*p = (int)args[i];
+
+	/* call into ofw */
+	spin_lock_irqsave(&ofw_lock, flags);
+	ret = olpc_ofw_cif(ofw_args);
+	spin_unlock_irqrestore(&ofw_lock, flags);
+
+	if (!ret) {
+		for (i = 0; i < nr_res; i++, p++)
+			*((int *)res[i]) = *p;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__olpc_ofw);
+
+/* OFW cif _should_ be above this address */
+#define OFW_MIN 0xff000000
+
+/* OFW starts on a 1MB boundary */
+#define OFW_BOUND (1<<20)
+
+void __init olpc_ofw_detect(void)
+{
+	struct olpc_ofw_header *hdr = &boot_params.olpc_ofw_header;
+	unsigned long start;
+
+	/* ensure OFW booted us by checking for "OFW " string */
+	if (hdr->ofw_magic != OLPC_OFW_SIG)
+		return;
+
+	olpc_ofw_cif = (int (*)(int *))hdr->cif_handler;
+
+	if ((unsigned long)olpc_ofw_cif < OFW_MIN) {
+		printk(KERN_ERR "OFW detected, but cif has invalid address 0x%lx - disabling.\n",
+				(unsigned long)olpc_ofw_cif);
+		olpc_ofw_cif = NULL;
+		return;
+	}
+
+	/* determine where OFW starts in memory */
+	start = round_down((unsigned long)olpc_ofw_cif, OFW_BOUND);
+	printk(KERN_INFO "OFW detected in memory, cif @ 0x%lx (reserving top %ldMB)\n",
+			(unsigned long)olpc_ofw_cif, (-start) >> 20);
+	reserve_top_address(-start);
+}