xtensa: nommu support

Add support for !CONFIG_MMU setups.

Signed-off-by: Johannes Weiner <jw@emlix.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/include/asm/cacheflush.h

@@ -65,13 +65,17 @@ extern void __flush_invalidate_dcache_range(unsigned long, unsigned long);
 # define __flush_invalidate_dcache_range(p,s)	__invalidate_dcache_range(p,s)
 #endif
 
-#if (DCACHE_WAY_SIZE > PAGE_SIZE)
+#if defined(CONFIG_MMU) && (DCACHE_WAY_SIZE > PAGE_SIZE)
 extern void __flush_invalidate_dcache_page_alias(unsigned long, unsigned long);
+#else
+static inline void __flush_invalidate_dcache_page_alias(unsigned long virt,
+							unsigned long phys) { }
 #endif
-#if (ICACHE_WAY_SIZE > PAGE_SIZE)
+#if defined(CONFIG_MMU) && (ICACHE_WAY_SIZE > PAGE_SIZE)
 extern void __invalidate_icache_page_alias(unsigned long, unsigned long);
 #else
-# define __invalidate_icache_page_alias(v,p)	do { } while(0)
+static inline void __invalidate_icache_page_alias(unsigned long virt,
+						unsigned long phys) { }
 #endif
 
 /*

arch/xtensa/include/asm/dma.h

@@ -44,8 +44,9 @@
  *	the value desired).
  */
 
+#ifndef MAX_DMA_ADDRESS
 #define MAX_DMA_ADDRESS		(PAGE_OFFSET + XCHAL_KIO_SIZE - 1)
-
+#endif
 
 /* Reserve and release a DMA channel */
 extern int request_dma(unsigned int dmanr, const char * device_id);

arch/xtensa/include/asm/io.h

@@ -69,21 +69,28 @@ static inline void * phys_to_virt(unsigned long address)
 
 static inline void *ioremap(unsigned long offset, unsigned long size)
 {
+#ifdef CONFIG_MMU
 	if (offset >= XCHAL_KIO_PADDR
 	    && offset < XCHAL_KIO_PADDR + XCHAL_KIO_SIZE)
 		return (void*)(offset-XCHAL_KIO_PADDR+XCHAL_KIO_BYPASS_VADDR);
-
 	else
 		BUG();
+#else
+	return (void *)offset;
+#endif
 }
 
 static inline void *ioremap_nocache(unsigned long offset, unsigned long size)
 {
+#ifdef CONFIG_MMU
 	if (offset >= XCHAL_KIO_PADDR
 	    && offset < XCHAL_KIO_PADDR + XCHAL_KIO_SIZE)
 		return (void*)(offset-XCHAL_KIO_PADDR+XCHAL_KIO_CACHED_VADDR);
 	else
 		BUG();
+#else
+	return (void *)offset;
+#endif
 }
 
 static inline void iounmap(void *addr)

arch/xtensa/include/asm/mmu.h

@@ -11,7 +11,12 @@
 #ifndef _XTENSA_MMU_H
 #define _XTENSA_MMU_H
 
+#ifndef CONFIG_MMU
+#include <asm/nommu.h>
+#else
+
 /* Default "unsigned long" context */
 typedef unsigned long mm_context_t;
 
+#endif /* CONFIG_MMU */
 #endif	/* _XTENSA_MMU_H */

arch/xtensa/include/asm/mmu_context.h

@@ -13,6 +13,10 @@
 #ifndef _XTENSA_MMU_CONTEXT_H
 #define _XTENSA_MMU_CONTEXT_H
 
+#ifndef CONFIG_MMU
+#include <asm/nommu_context.h>
+#else
+
 #include <linux/stringify.h>
 #include <linux/sched.h>
 
@@ -133,4 +137,5 @@ static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 
 }
 
+#endif /* CONFIG_MMU */
 #endif /* _XTENSA_MMU_CONTEXT_H */

arch/xtensa/include/asm/nommu.h

@@ -0,0 +1,3 @@
+typedef struct {
+	unsigned long end_brk;
+} mm_context_t;

arch/xtensa/include/asm/nommu_context.h

@@ -0,0 +1,25 @@
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+}
+
+static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+	return 0;
+}
+
+static inline void destroy_context(struct mm_struct *mm)
+{
+}
+
+static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+}
+
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+				struct task_struct *tsk)
+{
+}
+
+static inline void deactivate_mm(struct task_struct *tsk, struct mm_struct *mm)
+{
+}

arch/xtensa/include/asm/page.h

@@ -33,8 +33,14 @@
 #define PAGE_SIZE		(__XTENSA_UL_CONST(1) << PAGE_SHIFT)
 #define PAGE_MASK		(~(PAGE_SIZE-1))
 
+#ifdef CONFIG_MMU
 #define PAGE_OFFSET		XCHAL_KSEG_CACHED_VADDR
 #define MAX_MEM_PFN		XCHAL_KSEG_SIZE
+#else
+#define PAGE_OFFSET		0
+#define MAX_MEM_PFN		(PLATFORM_DEFAULT_MEM_START + PLATFORM_DEFAULT_MEM_SIZE)
+#endif
+
 #define PGTABLE_START		0x80000000
 
 /*
@@ -165,8 +171,9 @@ extern void copy_user_page(void*, void*, unsigned long, struct page*);
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
 #define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
 
+#ifdef CONFIG_MMU
 #define WANT_PAGE_VIRTUAL
-
+#endif
 
 #endif /* __ASSEMBLY__ */
 

arch/xtensa/include/asm/pgtable.h

@@ -183,7 +183,15 @@ extern unsigned long empty_zero_page[1024];
 
 #define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
 
+#ifdef CONFIG_MMU
 extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
+extern void paging_init(void);
+extern void pgtable_cache_init(void);
+#else
+# define swapper_pg_dir NULL
+static inline void paging_init(void) { }
+static inline void pgtable_cache_init(void) { }
+#endif
 
 /*
  * The pmd contains the kernel virtual address of the pte page.
@@ -383,8 +391,6 @@ ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 
 #else
 
-extern void paging_init(void);
-
 #define kern_addr_valid(addr)	(1)
 
 extern  void update_mmu_cache(struct vm_area_struct * vma,
@@ -398,9 +404,6 @@ extern  void update_mmu_cache(struct vm_area_struct * vma,
 #define io_remap_pfn_range(vma,from,pfn,size,prot) \
                 remap_pfn_range(vma, from, pfn, size, prot)
 
-
-extern void pgtable_cache_init(void);
-
 typedef pte_t *pte_addr_t;
 
 #endif /* !defined (__ASSEMBLY__) */

arch/xtensa/include/asm/processor.h

@@ -13,6 +13,7 @@
 
 #include <variant/core.h>
 #include <asm/coprocessor.h>
+#include <platform/hardware.h>
 
 #include <linux/compiler.h>
 #include <asm/ptrace.h>
@@ -35,7 +36,12 @@
  * the 1 GB requirement applies to the stack as well.
  */
 
+#ifdef CONFIG_MMU
 #define TASK_SIZE	__XTENSA_UL_CONST(0x40000000)
+#else
+#define TASK_SIZE	(PLATFORM_DEFAULT_MEM_START + PLATFORM_DEFAULT_MEM_SIZE)
+#endif
+
 #define STACK_TOP	TASK_SIZE
 #define STACK_TOP_MAX	STACK_TOP
 

arch/xtensa/kernel/entry.S

@@ -1463,6 +1463,7 @@ ENTRY(_spill_registers)
 	callx0	a0		# should not return
 1:	j	1b
 
+#ifdef CONFIG_MMU
 /*
  * We should never get here. Bail out!
  */
@@ -1775,7 +1776,7 @@ ENTRY(fast_store_prohibited)
 	bbsi.l	a2, PS_UM_BIT, 1f
 	j	_kernel_exception
 1:	j	_user_exception
-
+#endif /* CONFIG_MMU */
 
 /*
  * System Calls.

arch/xtensa/kernel/head.S

@@ -235,8 +235,9 @@ should_never_return:
  */
 
 .section ".bss.page_aligned", "w"
+#ifdef CONFIG_MMU
 ENTRY(swapper_pg_dir)
 	.fill	PAGE_SIZE, 1, 0
+#endif
 ENTRY(empty_zero_page)
 	.fill	PAGE_SIZE, 1, 0
-

arch/xtensa/kernel/setup.c

@@ -84,7 +84,13 @@ sysmem_info_t __initdata sysmem;
 int initrd_is_mapped;
 #endif
 
+#ifdef CONFIG_MMU
 extern void init_mmu(void);
+#else
+static inline void init_mmu(void) { }
+#endif
+
+extern void zones_init(void);
 
 /*
  * Boot parameter parsing.
@@ -286,6 +292,7 @@ void __init setup_arch(char **cmdline_p)
 
 
 	paging_init();
+	zones_init();
 
 #ifdef CONFIG_VT
 # if defined(CONFIG_VGA_CONSOLE)

arch/xtensa/kernel/traps.c

@@ -104,6 +104,7 @@ static dispatch_init_table_t __initdata dispatch_init_table[] = {
 #endif
 { EXCCAUSE_UNALIGNED,		KRNL,	   fast_unaligned },
 #endif
+#ifdef CONFIG_MMU
 { EXCCAUSE_ITLB_MISS,		0,	   do_page_fault },
 { EXCCAUSE_ITLB_MISS,		USER|KRNL, fast_second_level_miss},
 { EXCCAUSE_ITLB_MULTIHIT,		0,	   do_multihit },
@@ -118,6 +119,7 @@ static dispatch_init_table_t __initdata dispatch_init_table[] = {
 { EXCCAUSE_STORE_CACHE_ATTRIBUTE,	USER|KRNL, fast_store_prohibited },
 { EXCCAUSE_STORE_CACHE_ATTRIBUTE,	0,	   do_page_fault },
 { EXCCAUSE_LOAD_CACHE_ATTRIBUTE,	0,	   do_page_fault },
+#endif /* CONFIG_MMU */
 /* XCCHAL_EXCCAUSE_FLOATING_POINT unhandled */
 #if XTENSA_HAVE_COPROCESSOR(0)
 COPROCESSOR(0),

arch/xtensa/kernel/vectors.S

@@ -309,6 +309,7 @@ ENTRY(_DoubleExceptionVector)
 	 * All other exceptions are unexpected and thus unrecoverable!
 	 */
 
+#ifdef CONFIG_MMU
 	.extern fast_second_level_miss_double_kernel
 
 .Lksp:	/* a0: a0, a1: a1, a2: a2, a3: trashed, depc: depc, excsave: a3 */
@@ -319,6 +320,9 @@ ENTRY(_DoubleExceptionVector)
 	bnez	a3, .Lunrecoverable
 1:	movi	a3, fast_second_level_miss_double_kernel
 	jx	a3
+#else
+.equ	.Lksp,	.Lunrecoverable
+#endif
 
 	/* Critical! We can't handle this situation. PANIC! */
 

arch/xtensa/mm/Makefile

@@ -2,4 +2,5 @@
 # Makefile for the Linux/Xtensa-specific parts of the memory manager.
 #
 
-obj-y	 := init.o fault.o tlb.o misc.o cache.o
+obj-y			:= init.o cache.o misc.o
+obj-$(CONFIG_MMU)	+= fault.o mmu.o tlb.o

arch/xtensa/mm/init.c

@@ -24,15 +24,8 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 
-#include <asm/pgtable.h>
 #include <asm/bootparam.h>
-#include <asm/mmu_context.h>
-#include <asm/tlb.h>
 #include <asm/page.h>
-#include <asm/pgalloc.h>
-
-
-DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 
 /* References to section boundaries */
 
@@ -160,7 +153,7 @@ void __init bootmem_init(void)
 }
 
 
-void __init paging_init(void)
+void __init zones_init(void)
 {
 	unsigned long zones_size[MAX_NR_ZONES];
 	int i;
@@ -175,42 +168,9 @@ void __init paging_init(void)
 	zones_size[ZONE_HIGHMEM] = max_pfn - max_low_pfn;
 #endif
 
-	/* Initialize the kernel's page tables. */
-
-	memset(swapper_pg_dir, 0, PAGE_SIZE);
-
 	free_area_init_node(0, zones_size, ARCH_PFN_OFFSET, NULL);
 }
 
-/*
- * Flush the mmu and reset associated register to default values.
- */
-
-void __init init_mmu (void)
-{
-	/* Writing zeros to the <t>TLBCFG special registers ensure
-	 * that valid values exist in the register.  For existing
-	 * PGSZID<w> fields, zero selects the first element of the
-	 * page-size array.  For nonexistent PGSZID<w> fields, zero is
-	 * the best value to write.  Also, when changing PGSZID<w>
-	 * fields, the corresponding TLB must be flushed.
-	 */
-	set_itlbcfg_register (0);
-	set_dtlbcfg_register (0);
-	flush_tlb_all ();
-
-	/* Set rasid register to a known value. */
-
-	set_rasid_register (ASID_USER_FIRST);
-
-	/* Set PTEVADDR special register to the start of the page
-	 * table, which is in kernel mappable space (ie. not
-	 * statically mapped).  This register's value is undefined on
-	 * reset.
-	 */
-	set_ptevaddr_register (PGTABLE_START);
-}
-
 /*
  * Initialize memory pages.
  */
@@ -281,23 +241,3 @@ void free_initmem(void)
 	printk("Freeing unused kernel memory: %dk freed\n",
 	       (&__init_end - &__init_begin) >> 10);
 }
-
-struct kmem_cache *pgtable_cache __read_mostly;
-
-static void pgd_ctor(void* addr)
-{
-	pte_t* ptep = (pte_t*)addr;
-	int i;
-
-	for (i = 0; i < 1024; i++, ptep++)
-		pte_clear(NULL, 0, ptep);
-
-}
-
-void __init pgtable_cache_init(void)
-{
-	pgtable_cache = kmem_cache_create("pgd",
-			PAGE_SIZE, PAGE_SIZE,
-			SLAB_HWCACHE_ALIGN,
-			pgd_ctor);
-}