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>

2 files changed, 10 insertions, 15 deletions

diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index f3a1ea9d7fe4..26237357a88c 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -570,6 +570,7 @@ finish_tlb_load:
         rlwimi  r10,r12,29,30,30                /* DIRTY -> SW position */
         and     r11,r12,r10                     /* Mask PTE bits to keep */
         andi.   r10,r12,_PAGE_USER              /* User page ? */
+        ori     r11,r11,_PAGE_GUARDED           /* 440 errata, needs G set */
         beq     1f                              /* nope, leave U bits empty */
         rlwimi  r11,r11,3,26,28                 /* yes, copy S bits to U */
 1:      tlbwe   r11,r13,PPC44x_TLB_ATTRIB       /* Write ATTRIB */
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 1a32db331a5c..2538030954d8 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -370,13 +370,10 @@ static pgprot_t __pci_mmap_set_pgprot(struct pci_dev *dev, struct resource *rp,
         }
 
         /* XXX would be nice to have a way to ask for write-through */
-        prot |= _PAGE_NO_CACHE;
         if (write_combine)
-                prot &= ~_PAGE_GUARDED;
+                return pgprot_noncached_wc(prot);
         else
-                prot |= _PAGE_GUARDED;
-
-        return __pgprot(prot);
+                return pgprot_noncached(prot);
 }
 
 /*
@@ -387,19 +384,17 @@ static pgprot_t __pci_mmap_set_pgprot(struct pci_dev *dev, struct resource *rp,
 pgprot_t pci_phys_mem_access_prot(struct file *file,
                                   unsigned long pfn,
                                   unsigned long size,
-                                  pgprot_t protection)
+                                  pgprot_t prot)
 {
         struct pci_dev *pdev = NULL;
         struct resource *found = NULL;
-        unsigned long prot = pgprot_val(protection);
         resource_size_t offset = ((resource_size_t)pfn) << PAGE_SHIFT;
         int i;
 
         if (page_is_ram(pfn))
-                return __pgprot(prot);
-
-        prot |= _PAGE_NO_CACHE | _PAGE_GUARDED;
+                return prot;
 
+        prot = pgprot_noncached(prot);
         for_each_pci_dev(pdev) {
                 for (i = 0; i <= PCI_ROM_RESOURCE; i++) {
                         struct resource *rp = &pdev->resource[i];
@@ -420,14 +415,14 @@ pgprot_t pci_phys_mem_access_prot(struct file *file,
         }
         if (found) {
                 if (found->flags & IORESOURCE_PREFETCH)
-                        prot &= ~_PAGE_GUARDED;
+                        prot = pgprot_noncached_wc(prot);
                 pci_dev_put(pdev);
         }
 
         pr_debug("PCI: Non-PCI map for %llx, prot: %lx\n",
-                 (unsigned long long)offset, prot);
+                 (unsigned long long)offset, pgprot_val(prot));
 
-        return __pgprot(prot);
+        return prot;
 }
 
 
@@ -583,8 +578,7 @@ int pci_mmap_legacy_page_range(struct pci_bus *bus,
         pr_debug(" -> mapping phys %llx\n", (unsigned long long)offset);
 
         vma->vm_pgoff = offset >> PAGE_SHIFT;
-        vma->vm_page_prot = __pgprot(pgprot_val(vma->vm_page_prot)
-                                     | _PAGE_NO_CACHE | _PAGE_GUARDED);
+        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
         return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
                                vma->vm_end - vma->vm_start,
                                vma->vm_page_prot);