powerpc/mm: Rework usage of _PAGE_COHERENT/NO_CACHE/GUARDED

Currently, we never set _PAGE_COHERENT in the PTEs, we just OR it in
in the hash code based on some CPU feature bit.  We also manipulate
_PAGE_NO_CACHE and _PAGE_GUARDED by hand in all sorts of places.

This changes the logic so that instead, the PTE now contains
_PAGE_COHERENT for all normal RAM pages thay have I = 0 on platforms
that need it.  The hash code clears it if the feature bit is not set.

It also adds some clean accessors to setup various valid combinations
of access flags and change various bits of code to use them instead.

This should help having the PTE actually containing the bit
combinations that we really want.

I also removed _PAGE_GUARDED from _PAGE_BASE on 44x and instead
set it explicitely from the TLB miss.  I will ultimately remove it
completely as it appears that it might not be needed after all
but in the meantime, having it in the TLB miss makes things a
lot easier.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 17 insertions, 25 deletions

diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h
index 6ab7c67cb5a..f69a4d97772 100644
--- a/arch/powerpc/include/asm/pgtable-ppc32.h
+++ b/arch/powerpc/include/asm/pgtable-ppc32.h
@@ -228,9 +228,10 @@ extern int icache_44x_need_flush;
  *   - FILE *must* be in the bottom three bits because swap cache
  *     entries use the top 29 bits for TLB2.
  *
- *   - CACHE COHERENT bit (M) has no effect on PPC440 core, because it
- *     doesn't support SMP. So we can use this as software bit, like
- *     DIRTY.
+ *   - CACHE COHERENT bit (M) has no effect on original PPC440 cores,
+ *     because it doesn't support SMP. However, some later 460 variants
+ *     have -some- form of SMP support and so I keep the bit there for
+ *     future use
  *
  * With the PPC 44x Linux implementation, the 0-11th LSBs of the PTE are used
  * for memory protection related functions (see PTE structure in
@@ -436,20 +437,23 @@ extern int icache_44x_need_flush;
                          _PAGE_USER | _PAGE_ACCESSED | \
                          _PAGE_RW | _PAGE_HWWRITE | _PAGE_DIRTY | \
                          _PAGE_EXEC | _PAGE_HWEXEC)
+
 /*
- * Note: the _PAGE_COHERENT bit automatically gets set in the hardware
- * PTE if CONFIG_SMP is defined (hash_page does this); there is no need
- * to have it in the Linux PTE, and in fact the bit could be reused for
- * another purpose.  -- paulus.
+ * We define 2 sets of base prot bits, one for basic pages (ie,
+ * cacheable kernel and user pages) and one for non cacheable
+ * pages. We always set _PAGE_COHERENT when SMP is enabled or
+ * the processor might need it for DMA coherency.
  */
-
-#ifdef CONFIG_44x
-#define _PAGE_BASE      (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_GUARDED)
+#if defined(CONFIG_SMP) || defined(CONFIG_PPC_STD_MMU)
+#define _PAGE_BASE      (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_COHERENT)
 #else
 #define _PAGE_BASE      (_PAGE_PRESENT | _PAGE_ACCESSED)
 #endif
+#define _PAGE_BASE_NC   (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_NO_CACHE)
+
 #define _PAGE_WRENABLE  (_PAGE_RW | _PAGE_DIRTY | _PAGE_HWWRITE)
 #define _PAGE_KERNEL    (_PAGE_BASE | _PAGE_SHARED | _PAGE_WRENABLE)
+#define _PAGE_KERNEL_NC (_PAGE_BASE_NC | _PAGE_SHARED | _PAGE_WRENABLE)
 
 #ifdef CONFIG_PPC_STD_MMU
 /* On standard PPC MMU, no user access implies kernel read/write access,
@@ -459,7 +463,7 @@ extern int icache_44x_need_flush;
 #define _PAGE_KERNEL_RO (_PAGE_BASE | _PAGE_SHARED)
 #endif
 
-#define _PAGE_IO        (_PAGE_KERNEL | _PAGE_NO_CACHE | _PAGE_GUARDED)
+#define _PAGE_IO        (_PAGE_KERNEL_NC | _PAGE_GUARDED)
 #define _PAGE_RAM       (_PAGE_KERNEL | _PAGE_HWEXEC)
 
 #if defined(CONFIG_KGDB) || defined(CONFIG_XMON) || defined(CONFIG_BDI_SWITCH) ||\
@@ -552,9 +556,6 @@ static inline int pte_young(pte_t pte)		{ return pte_val(pte) & _PAGE_ACCESSED;
 static inline int pte_file(pte_t pte)           { return pte_val(pte) & _PAGE_FILE; }
 static inline int pte_special(pte_t pte)        { return pte_val(pte) & _PAGE_SPECIAL; }
 
-static inline void pte_uncache(pte_t pte)       { pte_val(pte) |= _PAGE_NO_CACHE; }
-static inline void pte_cache(pte_t pte)         { pte_val(pte) &= ~_PAGE_NO_CACHE; }
-
 static inline pte_t pte_wrprotect(pte_t pte) {
         pte_val(pte) &= ~(_PAGE_RW | _PAGE_HWWRITE); return pte; }
 static inline pte_t pte_mkclean(pte_t pte) {
@@ -693,10 +694,11 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 #endif
 }
 
+
 static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
                               pte_t *ptep, pte_t pte)
 {
-#if defined(CONFIG_PTE_64BIT) && defined(CONFIG_SMP)
+#if defined(CONFIG_PTE_64BIT) && defined(CONFIG_SMP) && defined(CONFIG_DEBUG_VM)
         WARN_ON(pte_present(*ptep));
 #endif
         __set_pte_at(mm, addr, ptep, pte);
@@ -760,16 +762,6 @@ static inline void __ptep_set_access_flags(pte_t *ptep, pte_t entry, int dirty)
         __changed;                                                         \
 })
 
-/*
- * Macro to mark a page protection value as "uncacheable".
- */
-#define pgprot_noncached(prot)  (__pgprot(pgprot_val(prot) | _PAGE_NO_CACHE | _PAGE_GUARDED))
-
-struct file;
-extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
-                                     unsigned long size, pgprot_t vma_prot);
-#define __HAVE_PHYS_MEM_ACCESS_PROT
-
 #define __HAVE_ARCH_PTE_SAME
 #define pte_same(A,B)   (((pte_val(A) ^ pte_val(B)) & ~_PAGE_HASHPTE) == 0)