[PATCH] sh: fixmap support.

From: Paul Mundt <lethal@Linux-SH.ORG>

This adds fixmap support for sh.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/sh/mm/init.c

@@ -3,7 +3,7 @@
  *  linux/arch/sh/mm/init.c
  *
  *  Copyright (C) 1999  Niibe Yutaka
- *  Copyright (C) 2002  Paul Mundt
+ *  Copyright (C) 2002, 2004  Paul Mundt
  *
  *  Based on linux/arch/i386/mm/init.c:
  *   Copyright (C) 1995  Linus Torvalds
@@ -83,6 +83,66 @@ void show_mem(void)
 	printk("%d pages swap cached\n",cached);
 }
 
+static void set_pte_phys(unsigned long addr, unsigned long phys, pgprot_t prot)
+{
+	pgd_t *pgd;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	pgd = swapper_pg_dir + pgd_index(addr);
+	if (pgd_none(*pgd)) {
+		pgd_ERROR(*pgd);
+		return;
+	}
+
+	pmd = pmd_offset(pgd, addr);
+	if (pmd_none(*pmd)) {
+		pte = (pte_t *)get_zeroed_page(GFP_ATOMIC);
+		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE | _PAGE_USER));
+		if (pte != pte_offset_kernel(pmd, 0)) {
+			pmd_ERROR(*pmd);
+			return;
+		}
+	}
+
+	pte = pte_offset_kernel(pmd, addr);
+	if (!pte_none(*pte)) {
+		pte_ERROR(*pte);
+		return;
+	}
+
+	set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, prot));
+
+	__flush_tlb_page(get_asid(), addr);
+}
+
+/*
+ * As a performance optimization, other platforms preserve the fixmap mapping
+ * across a context switch, we don't presently do this, but this could be done
+ * in a similar fashion as to the wired TLB interface that sh64 uses (by way
+ * of the memorry mapped UTLB configuration) -- this unfortunately forces us to
+ * give up a TLB entry for each mapping we want to preserve. While this may be
+ * viable for a small number of fixmaps, it's not particularly useful for
+ * everything and needs to be carefully evaluated. (ie, we may want this for
+ * the vsyscall page).
+ *
+ * XXX: Perhaps add a _PAGE_WIRED flag or something similar that we can pass
+ * in at __set_fixmap() time to determine the appropriate behavior to follow.
+ *
+ *					 -- PFM.
+ */
+void __set_fixmap(enum fixed_addresses idx, unsigned long phys, pgprot_t prot)
+{
+	unsigned long address = __fix_to_virt(idx);
+
+	if (idx >= __end_of_fixed_addresses) {
+		BUG();
+		return;
+	}
+
+	set_pte_phys(address, phys, prot);
+}
+
 /* References to section boundaries */
 
 extern char _text, _etext, _edata, __bss_start, _end;

include/asm-sh/fixmap.h

+/*
+ * fixmap.h: compile-time virtual memory allocation
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 1998 Ingo Molnar
+ *
+ * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
+ */
+
+#ifndef _ASM_FIXMAP_H
+#define _ASM_FIXMAP_H
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <asm/page.h>
+#ifdef CONFIG_HIGHMEM
+#include <linux/threads.h>
+#include <asm/kmap_types.h>
+#endif
+
+/*
+ * Here we define all the compile-time 'special' virtual
+ * addresses. The point is to have a constant address at
+ * compile time, but to set the physical address only
+ * in the boot process. We allocate these special  addresses
+ * from the end of virtual memory (0xfffff000) backwards.
+ * Also this lets us do fail-safe vmalloc(), we
+ * can guarantee that these special addresses and
+ * vmalloc()-ed addresses never overlap.
+ *
+ * these 'compile-time allocated' memory buffers are
+ * fixed-size 4k pages. (or larger if used with an increment
+ * highger than 1) use fixmap_set(idx,phys) to associate
+ * physical memory with fixmap indices.
+ *
+ * TLB entries of such buffers will not be flushed across
+ * task switches.
+ */
+
+/*
+ * on UP currently we will have no trace of the fixmap mechanizm,
+ * no page table allocations, etc. This might change in the
+ * future, say framebuffers for the console driver(s) could be
+ * fix-mapped?
+ */
+enum fixed_addresses {
+#ifdef CONFIG_HIGHMEM
+	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */
+	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
+#endif
+	__end_of_fixed_addresses
+};
+
+extern void __set_fixmap (enum fixed_addresses idx,
+					unsigned long phys, pgprot_t flags);
+
+#define set_fixmap(idx, phys) \
+		__set_fixmap(idx, phys, PAGE_KERNEL)
+/*
+ * Some hardware wants to get fixmapped without caching.
+ */
+#define set_fixmap_nocache(idx, phys) \
+		__set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
+/*
+ * used by vmalloc.c.
+ *
+ * Leave one empty page between vmalloc'ed areas and
+ * the start of the fixmap, and leave one page empty
+ * at the top of mem..
+ */
+#define FIXADDR_TOP	(P4SEG - PAGE_SIZE)
+#define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
+#define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
+
+#define __fix_to_virt(x)	(FIXADDR_TOP - ((x) << PAGE_SHIFT))
+#define __virt_to_fix(x)	((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
+
+extern void __this_fixmap_does_not_exist(void);
+
+/*
+ * 'index to address' translation. If anyone tries to use the idx
+ * directly without tranlation, we catch the bug with a NULL-deference
+ * kernel oops. Illegal ranges of incoming indices are caught too.
+ */
+static inline unsigned long fix_to_virt(const unsigned int idx)
+{
+	/*
+	 * this branch gets completely eliminated after inlining,
+	 * except when someone tries to use fixaddr indices in an
+	 * illegal way. (such as mixing up address types or using
+	 * out-of-range indices).
+	 *
+	 * If it doesn't get removed, the linker will complain
+	 * loudly with a reasonably clear error message..
+	 */
+	if (idx >= __end_of_fixed_addresses)
+		__this_fixmap_does_not_exist();
+
+        return __fix_to_virt(idx);
+}
+
+static inline unsigned long virt_to_fix(const unsigned long vaddr)
+{
+	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
+	return __virt_to_fix(vaddr);
+}
+
+#endif

include/asm-sh/pgtable.h

@@ -3,7 +3,7 @@
 
 /*
  * Copyright (C) 1999 Niibe Yutaka
- * Copyright (C) 2002, 2003 Paul Mundt
+ * Copyright (C) 2002, 2003, 2004 Paul Mundt
  */
 
 #include <linux/config.h>
@@ -16,6 +16,7 @@
 #ifndef __ASSEMBLY__
 #include <asm/processor.h>
 #include <asm/addrspace.h>
+#include <asm/fixmap.h>
 #include <linux/threads.h>
 
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
@@ -51,7 +52,7 @@ extern unsigned long empty_zero_page[1024];
  * Currently only 4-enty (16kB) is used (see arch/sh/mm/cache.c)
  */
 #define VMALLOC_START	(P3SEG+0x00100000)
-#define VMALLOC_END	P4SEG
+#define VMALLOC_END	(FIXADDR_START-2*PAGE_SIZE)
 
 #define	_PAGE_WT	0x001  /* WT-bit on SH-4, 0 on SH-3 */
 #define _PAGE_HW_SHARED	0x002  /* SH-bit  : page is shared among processes */