ACPI: Page based coalescing of I/O remappings optimization

This patch optimizes ACPI MMIO remappings by keeping track of the
remappings on a PAGE_SIZE granularity.

When an ioremap() occurs, the underlying infrastructure works on a 'page'
based granularity.  As such, an ioremap() request for 1 byte for example,
will end up mapping in an entire (PAGE_SIZE) page.  Huang Ying took
advantage of this in commit 15651291a2f8c11e7e6a42d8bfde7a213ff13262 by
checking if subsequent ioremap() requests reside within any of the list's
existing remappings still in place, and if so, incrementing a reference
count on the existing mapping as opposed to performing another ioremap().

Signed-off-by: Myron Stowe <myron.stowe@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 3282689..885e222 100644 (file)
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -104,6 +104,7 @@ struct acpi_ioremap {
        void __iomem *virt;
        acpi_physical_address phys;
        acpi_size size;
+       struct kref ref;
 };
 
 static LIST_HEAD(acpi_ioremaps);
@@ -245,15 +246,28 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 }
 
 /* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
-static void __iomem *
-acpi_map_vaddr_lookup(acpi_physical_address phys, acpi_size size)
+static struct acpi_ioremap *
+acpi_map_lookup(acpi_physical_address phys, acpi_size size)
 {
        struct acpi_ioremap *map;
 
        list_for_each_entry_rcu(map, &acpi_ioremaps, list)
                if (map->phys <= phys &&
                    phys + size <= map->phys + map->size)
-                       return map->virt + (phys - map->phys);
+                       return map;
+
+       return NULL;
+}
+
+/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
+static void __iomem *
+acpi_map_vaddr_lookup(acpi_physical_address phys, unsigned int size)
+{
+       struct acpi_ioremap *map;
+
+       map = acpi_map_lookup(phys, size);
+       if (map)
+               return map->virt + (phys - map->phys);
 
        return NULL;
 }
@@ -265,7 +279,8 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
        struct acpi_ioremap *map;
 
        list_for_each_entry_rcu(map, &acpi_ioremaps, list)
-               if (map->virt == virt && map->size == size)
+               if (map->virt <= virt &&
+                   virt + size <= map->virt + map->size)
                        return map;
 
        return NULL;
@@ -274,9 +289,10 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
 void __iomem *__init_refok
 acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 {
-       struct acpi_ioremap *map;
-       unsigned long flags;
+       struct acpi_ioremap *map, *tmp_map;
+       unsigned long flags, pg_sz;
        void __iomem *virt;
+       phys_addr_t pg_off;
 
        if (phys > ULONG_MAX) {
                printk(KERN_ERR PREFIX "Cannot map memory that high\n");
@@ -290,7 +306,9 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
        if (!map)
                return NULL;
 
-       virt = ioremap(phys, size);
+       pg_off = round_down(phys, PAGE_SIZE);
+       pg_sz = round_up(phys + size, PAGE_SIZE) - pg_off;
+       virt = ioremap(pg_off, pg_sz);
        if (!virt) {
                kfree(map);
                return NULL;
@@ -298,21 +316,40 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 
        INIT_LIST_HEAD(&map->list);
        map->virt = virt;
-       map->phys = phys;
-       map->size = size;
+       map->phys = pg_off;
+       map->size = pg_sz;
+       kref_init(&map->ref);
 
        spin_lock_irqsave(&acpi_ioremap_lock, flags);
+       /* Check if page has already been mapped. */
+       tmp_map = acpi_map_lookup(phys, size);
+       if (tmp_map) {
+               kref_get(&tmp_map->ref);
+               spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
+               iounmap(map->virt);
+               kfree(map);
+               return tmp_map->virt + (phys - tmp_map->phys);
+       }
        list_add_tail_rcu(&map->list, &acpi_ioremaps);
        spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
 
-       return virt;
+       return map->virt + (phys - map->phys);
 }
 EXPORT_SYMBOL_GPL(acpi_os_map_memory);
 
+static void acpi_kref_del_iomap(struct kref *ref)
+{
+       struct acpi_ioremap *map;
+
+       map = container_of(ref, struct acpi_ioremap, ref);
+       list_del_rcu(&map->list);
+}
+
 void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
 {
        struct acpi_ioremap *map;
        unsigned long flags;
+       int del;
 
        if (!acpi_gbl_permanent_mmap) {
                __acpi_unmap_table(virt, size);
@@ -328,9 +365,12 @@ void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
                return;
        }
 
-       list_del_rcu(&map->list);
+       del = kref_put(&map->ref, acpi_kref_del_iomap);
        spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
 
+       if (!del)
+               return;
+
        synchronize_rcu();
        iounmap(map->virt);
        kfree(map);