[POWERPC] Port fixmap from x86 and use for kmap_atomic

The fixmap code from x86 allows us to have compile time virtual addresses
that we change the physical addresses of at run time.

This is useful for applications like kmap_atomic, PCI config that is done
via direct memory map, kexec/kdump.

We got ride of CONFIG_HIGHMEM_START as we can now determine a more optimal
location for PKMAP_BASE based on where the fixmap addresses start and
working back from there.

Additionally, the kmap code in asm-powerpc/highmem.h always had debug
enabled.  Moved to using CONFIG_DEBUG_HIGHMEM to determine if we should
have the extra debug checking.

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

1 files changed, 22 insertions, 19 deletions

diff --git a/include/asm-powerpc/highmem.h b/include/asm-powerpc/highmem.h
index f7b21ee302b4..5d99b6489d56 100644
--- a/include/asm-powerpc/highmem.h
+++ b/include/asm-powerpc/highmem.h
@@ -27,9 +27,7 @@
 #include <asm/kmap_types.h>
 #include <asm/tlbflush.h>
 #include <asm/page.h>
-
-/* undef for production */
-#define HIGHMEM_DEBUG 1
+#include <asm/fixmap.h>
 
 extern pte_t *kmap_pte;
 extern pgprot_t kmap_prot;
@@ -40,14 +38,12 @@ extern pte_t *pkmap_page_table;
  * easily, subsequent pte tables have to be allocated in one physical
  * chunk of RAM.
  */
-#define PKMAP_BASE      CONFIG_HIGHMEM_START
 #define LAST_PKMAP      (1 << PTE_SHIFT)
 #define LAST_PKMAP_MASK (LAST_PKMAP-1)
+#define PKMAP_BASE      ((FIXADDR_START - PAGE_SIZE*(LAST_PKMAP + 1)) & PMD_MASK)
 #define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
 
-#define KMAP_FIX_BEGIN  (PKMAP_BASE + 0x00400000UL)
-
 extern void *kmap_high(struct page *page);
 extern void kunmap_high(struct page *page);
 
@@ -73,7 +69,7 @@ static inline void kunmap(struct page *page)
  * be used in IRQ contexts, so in some (very limited) cases we need
  * it.
  */
-static inline void *kmap_atomic(struct page *page, enum km_type type)
+static inline void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
 {
         unsigned int idx;
         unsigned long vaddr;
@@ -84,34 +80,39 @@ static inline void *kmap_atomic(struct page *page, enum km_type type)
                 return page_address(page);
 
         idx = type + KM_TYPE_NR*smp_processor_id();
-        vaddr = KMAP_FIX_BEGIN + idx * PAGE_SIZE;
-#ifdef HIGHMEM_DEBUG
-        BUG_ON(!pte_none(*(kmap_pte+idx)));
+        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+#ifdef CONFIG_DEBUG_HIGHMEM
+        BUG_ON(!pte_none(*(kmap_pte-idx)));
 #endif
-        set_pte_at(&init_mm, vaddr, kmap_pte+idx, mk_pte(page, kmap_prot));
+        set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
         flush_tlb_page(NULL, vaddr);
 
         return (void*) vaddr;
 }
 
+static inline void *kmap_atomic(struct page *page, enum km_type type)
+{
+        return kmap_atomic_prot(page, type, kmap_prot);
+}
+
 static inline void kunmap_atomic(void *kvaddr, enum km_type type)
 {
-#ifdef HIGHMEM_DEBUG
+#ifdef CONFIG_DEBUG_HIGHMEM
         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-        unsigned int idx = type + KM_TYPE_NR*smp_processor_id();
+        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
 
-        if (vaddr < KMAP_FIX_BEGIN) { // FIXME
+        if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
                 pagefault_enable();
                 return;
         }
 
-        BUG_ON(vaddr != KMAP_FIX_BEGIN + idx * PAGE_SIZE);
+        BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 
         /*
          * force other mappings to Oops if they'll try to access
          * this pte without first remap it
          */
-        pte_clear(&init_mm, vaddr, kmap_pte+idx);
+        pte_clear(&init_mm, vaddr, kmap_pte-idx);
         flush_tlb_page(NULL, vaddr);
 #endif
         pagefault_enable();
@@ -120,12 +121,14 @@ static inline void kunmap_atomic(void *kvaddr, enum km_type type)
 static inline struct page *kmap_atomic_to_page(void *ptr)
 {
         unsigned long idx, vaddr = (unsigned long) ptr;
+        pte_t *pte;
 
-        if (vaddr < KMAP_FIX_BEGIN)
+        if (vaddr < FIXADDR_START)
                 return virt_to_page(ptr);
 
-        idx = (vaddr - KMAP_FIX_BEGIN) >> PAGE_SHIFT;
-        return pte_page(kmap_pte[idx]);
+        idx = virt_to_fix(vaddr);
+        pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
+        return pte_page(*pte);
 }
 
 #define flush_cache_kmaps()     flush_cache_all()