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/include/asm/fixmap.h

@@ -60,6 +60,14 @@ enum fixed_addresses {
 	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */
 	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
 #endif
+	/*
+	 * FIX_IOREMAP entries are useful for mapping physical address
+	 * space before ioremap() is useable, e.g. really early in boot
+	 * before kmalloc() is working.
+	 */
+#define FIX_N_IOREMAPS	32
+	FIX_IOREMAP_BEGIN,
+	FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS,
 	__end_of_fixed_addresses
 };
 

arch/sh/include/asm/io.h

@@ -237,6 +237,12 @@ void __iomem *__ioremap_caller(unsigned long offset, unsigned long size,
 			       unsigned long flags, void *caller);
 void __iounmap(void __iomem *addr);
 
+#ifdef CONFIG_IOREMAP_FIXED
+extern void __iomem *ioremap_fixed(resource_size_t, unsigned long, pgprot_t);
+extern void iounmap_fixed(void __iomem *);
+extern void ioremap_fixed_init(void);
+#endif
+
 static inline void __iomem *
 __ioremap(unsigned long offset, unsigned long size, unsigned long flags)
 {

arch/sh/kernel/setup.c

@@ -449,14 +449,15 @@ void __init setup_arch(char **cmdline_p)
 #ifdef CONFIG_DUMMY_CONSOLE
 	conswitchp = &dummy_con;
 #endif
+	paging_init();
+	pmb_init();
+
+	ioremap_fixed_init();
 
 	/* Perform the machine specific initialisation */
 	if (likely(sh_mv.mv_setup))
 		sh_mv.mv_setup(cmdline_p);
 
-	paging_init();
-	pmb_init();
-
 #ifdef CONFIG_SMP
 	plat_smp_setup();
 #endif

arch/sh/mm/Kconfig

@@ -169,6 +169,10 @@ config ARCH_MEMORY_PROBE
 	def_bool y
 	depends on MEMORY_HOTPLUG
 
+config IOREMAP_FIXED
+       def_bool y
+       depends on X2TLB || SUPERH64
+
 choice
 	prompt "Kernel page size"
 	default PAGE_SIZE_4KB

arch/sh/mm/Makefile

@@ -35,6 +35,7 @@ endif
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_PMB)		+= pmb.o
 obj-$(CONFIG_NUMA)		+= numa.o
+obj-$(CONFIG_IOREMAP_FIXED)	+= ioremap_fixed.o
 
 # Special flags for fault_64.o.  This puts restrictions on the number of
 # caller-save registers that the compiler can target when building this file.

arch/sh/mm/ioremap_fixed.c

+/*
+ * 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;
+}