sh: Add fixed ioremap support

Some devices need to be ioremap'd and accessed very early in the boot
process. It is not possible to use the standard ioremap() function in
this case because that requires kmalloc()'ing some virtual address space
and kmalloc() may not be available so early in boot.

This patch provides fixmap mappings that allow physical address ranges
to be remapped into the kernel address space during the early boot
stages.

Signed-off-by: Matt Fleming <matt@console-pimps.org>

arch/sh/mm/ioremap_fixed.c

@@ -0,0 +1,144 @@
+/*
+ * Re-map IO memory to kernel address space so that we can access it.
+ *
+ * These functions should only be used when it is necessary to map a
+ * physical address space into the kernel address space before ioremap()
+ * can be used, e.g. early in boot before paging_init().
+ *
+ * Copyright (C) 2009  Matt Fleming
+ */
+
+#include <linux/vmalloc.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/io.h>
+#include <linux/bootmem.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <asm/fixmap.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/addrspace.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+
+struct ioremap_map {
+	void __iomem *addr;
+	unsigned long size;
+	unsigned long fixmap_addr;
+};
+
+static struct ioremap_map ioremap_maps[FIX_N_IOREMAPS];
+
+void __init ioremap_fixed_init(void)
+{
+	struct ioremap_map *map;
+	int i;
+
+	for (i = 0; i < FIX_N_IOREMAPS; i++) {
+		map = &ioremap_maps[i];
+		map->fixmap_addr = __fix_to_virt(FIX_IOREMAP_BEGIN + i);
+	}
+}
+
+void __init __iomem *
+ioremap_fixed(resource_size_t phys_addr, unsigned long size, pgprot_t prot)
+{
+	enum fixed_addresses idx0, idx;
+	resource_size_t last_addr;
+	struct ioremap_map *map;
+	unsigned long offset;
+	unsigned int nrpages;
+	int i, slot;
+
+	slot = -1;
+	for (i = 0; i < FIX_N_IOREMAPS; i++) {
+		map = &ioremap_maps[i];
+		if (!map->addr) {
+			map->size = size;
+			slot = i;
+			break;
+		}
+	}
+
+	if (slot < 0)
+		return NULL;
+
+	/* Don't allow wraparound or zero size */
+	last_addr = phys_addr + size - 1;
+	if (!size || last_addr < phys_addr)
+		return NULL;
+
+	/*
+	 * Fixmap mappings have to be page-aligned
+	 */
+	offset = phys_addr & ~PAGE_MASK;
+	phys_addr &= PAGE_MASK;
+	size = PAGE_ALIGN(last_addr + 1) - phys_addr;
+
+	/*
+	 * Mappings have to fit in the FIX_IOREMAP area.
+	 */
+	nrpages = size >> PAGE_SHIFT;
+	if (nrpages > FIX_N_IOREMAPS)
+		return NULL;
+
+	/*
+	 * Ok, go for it..
+	 */
+	idx0 = FIX_IOREMAP_BEGIN + slot;
+	idx = idx0;
+	while (nrpages > 0) {
+		pgprot_val(prot) |= _PAGE_WIRED;
+		__set_fixmap(idx, phys_addr, prot);
+		phys_addr += PAGE_SIZE;
+		idx++;
+		--nrpages;
+	}
+
+	map->addr = (void __iomem *)(offset + map->fixmap_addr);
+	return map->addr;
+}
+
+void __init iounmap_fixed(void __iomem *addr)
+{
+	enum fixed_addresses idx;
+	unsigned long virt_addr;
+	struct ioremap_map *map;
+	unsigned long offset;
+	unsigned int nrpages;
+	int i, slot;
+	pgprot_t prot;
+
+	slot = -1;
+	for (i = 0; i < FIX_N_IOREMAPS; i++) {
+		map = &ioremap_maps[i];
+		if (map->addr == addr) {
+			slot = i;
+			break;
+		}
+	}
+
+	if (slot < 0)
+		return;
+
+	virt_addr = (unsigned long)addr;
+
+	offset = virt_addr & ~PAGE_MASK;
+	nrpages = PAGE_ALIGN(offset + map->size - 1) >> PAGE_SHIFT;
+
+	pgprot_val(prot) = _PAGE_WIRED;
+
+	idx = FIX_IOREMAP_BEGIN + slot + nrpages;
+	while (nrpages > 0) {
+		__clear_fixmap(idx, prot);
+		--idx;
+		--nrpages;
+	}
+
+	map->size = 0;
+	map->addr = NULL;
+}