[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>

2 files changed, 128 insertions, 19 deletions

diff --git a/include/asm-powerpc/fixmap.h b/include/asm-powerpc/fixmap.h
new file mode 100644
index 000000000000..8428b38a3d30
--- /dev/null
+++ b/include/asm-powerpc/fixmap.h
@@ -0,0 +1,106 @@
+/*
+ * 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
+ *
+ * Copyright 2008 Freescale Semiconductor Inc.
+ *   Port to powerpc added by Kumar Gala
+ */
+
+#ifndef _ASM_FIXMAP_H
+#define _ASM_FIXMAP_H
+
+extern unsigned long FIXADDR_TOP;
+
+#ifndef __ASSEMBLY__
+#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.
+ */
+enum fixed_addresses {
+        FIX_HOLE,
+#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
+        /* FIX_PCIE_MCFG, */
+        __end_of_fixed_addresses
+};
+
+extern void __set_fixmap (enum fixed_addresses idx,
+                                        phys_addr_t 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)
+
+#define clear_fixmap(idx) \
+                __set_fixmap(idx, 0, __pgprot(0))
+
+#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 __always_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 /* !__ASSEMBLY__ */
+#endif
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()