ARM: add generic ioremap optimization by reusing static mappings

Now that we have all the static mappings from iotable_init() located
in the vmalloc area, it is trivial to optimize ioremap by reusing those
static mappings when the requested physical area fits in one of them,
and so in a generic way for all platforms.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Tested-by: Jamie Iles <jamie@jamieiles.com>

3 files changed, 64 insertions, 25 deletions

diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index bc7d9bd766d1..12c7ad215ce7 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -36,12 +36,6 @@
 #include <asm/mach/map.h>
 #include "mm.h"
 
-/*
- * Used by ioremap() and iounmap() code to mark (super)section-mapped
- * I/O regions in vm_struct->flags field.
- */
-#define VM_ARM_SECTION_MAPPING  0x80000000
-
 int ioremap_page(unsigned long virt, unsigned long phys,
                  const struct mem_type *mtype)
 {
@@ -201,12 +195,6 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
         if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
                 return NULL;
 
-        /*
-         * Don't allow RAM to be mapped - this causes problems with ARMv6+
-         */
-        if (WARN_ON(pfn_valid(pfn)))
-                return NULL;
-
         type = get_mem_type(mtype);
         if (!type)
                 return NULL;
@@ -216,6 +204,34 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
          */
         size = PAGE_ALIGN(offset + size);
 
+        /*
+         * Try to reuse one of the static mapping whenever possible.
+         */
+        read_lock(&vmlist_lock);
+        for (area = vmlist; area; area = area->next) {
+                if (!size || (sizeof(phys_addr_t) == 4 && pfn >= 0x100000))
+                        break;
+                if (!(area->flags & VM_ARM_STATIC_MAPPING))
+                        continue;
+                if ((area->flags & VM_ARM_MTYPE_MASK) != VM_ARM_MTYPE(mtype))
+                        continue;
+                if (__phys_to_pfn(area->phys_addr) > pfn ||
+                    __pfn_to_phys(pfn) + size-1 > area->phys_addr + area->size-1)
+                        continue;
+                /* we can drop the lock here as we know *area is static */
+                read_unlock(&vmlist_lock);
+                addr = (unsigned long)area->addr;
+                addr += __pfn_to_phys(pfn) - area->phys_addr;
+                return (void __iomem *) (offset + addr);
+        }
+        read_unlock(&vmlist_lock);
+
+        /*
+         * Don't allow RAM to be mapped - this causes problems with ARMv6+
+         */
+        if (WARN_ON(pfn_valid(pfn)))
+                return NULL;
+
         area = get_vm_area_caller(size, VM_IOREMAP, caller);
         if (!area)
                 return NULL;
@@ -313,26 +329,34 @@ __arm_ioremap_exec(unsigned long phys_addr, size_t size, bool cached)
 void __iounmap(volatile void __iomem *io_addr)
 {
         void *addr = (void *)(PAGE_MASK & (unsigned long)io_addr);
-#ifndef CONFIG_SMP
         struct vm_struct *vm;
 
-        /*
-         * If this is a section based mapping we need to handle it
-         * specially as the VM subsystem does not know how to handle
-         * such a beast.
-         */
         read_lock(&vmlist_lock);
         for (vm = vmlist; vm; vm = vm->next) {
-                if ((vm->flags & VM_IOREMAP) && (vm->addr == addr)) {
-                        if (vm->flags & VM_ARM_SECTION_MAPPING) {
-                                unmap_area_sections((unsigned long)vm->addr,
-                                                    vm->size);
-                        }
+                if (vm->addr > addr)
                         break;
+                if (!(vm->flags & VM_IOREMAP))
+                        continue;
+                /* If this is a static mapping we must leave it alone */
+                if ((vm->flags & VM_ARM_STATIC_MAPPING) &&
+                    (vm->addr <= addr) && (vm->addr + vm->size > addr)) {
+                        read_unlock(&vmlist_lock);
+                        return;
                 }
+#ifndef CONFIG_SMP
+                /*
+                 * If this is a section based mapping we need to handle it
+                 * specially as the VM subsystem does not know how to handle
+                 * such a beast.
+                 */
+                if ((vm->addr == addr) &&
+                    (vm->flags & VM_ARM_SECTION_MAPPING)) {
+                        unmap_area_sections((unsigned long)vm->addr, vm->size);
+                        break;
+                }
+#endif
         }
         read_unlock(&vmlist_lock);
-#endif
 
         vunmap(addr);
 }
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index ad7cce3bc431..70f6d3ea4834 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -21,6 +21,20 @@ const struct mem_type *get_mem_type(unsigned int type);
 
 extern void __flush_dcache_page(struct address_space *mapping, struct page *page);
 
+/*
+ * ARM specific vm_struct->flags bits.
+ */
+
+/* (super)section-mapped I/O regions used by ioremap()/iounmap() */
+#define VM_ARM_SECTION_MAPPING  0x80000000
+
+/* permanent static mappings from iotable_init() */
+#define VM_ARM_STATIC_MAPPING   0x40000000
+
+/* mapping type (attributes) for permanent static mappings */
+#define VM_ARM_MTYPE(mt)                ((mt) << 20)
+#define VM_ARM_MTYPE_MASK       (0x1f << 20)
+
 #endif
 
 #ifdef CONFIG_ZONE_DMA
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index c61481577ae1..27e366af67f9 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -749,7 +749,8 @@ void __init iotable_init(struct map_desc *io_desc, int nr)
                 vm->addr = (void *)(md->virtual & PAGE_MASK);
                 vm->size = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));
                 vm->phys_addr = __pfn_to_phys(md->pfn); 
-                vm->flags = VM_IOREMAP;
+                vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING; 
+                vm->flags |= VM_ARM_MTYPE(md->type);
                 vm->caller = iotable_init;
                 vm_area_add_early(vm++);
         }