[PATCH v3 2/3] ARM: static_vm: introduce an infrastructure for static mapped area

[Joonsoo Kim]

From: Joonsoo Kim <js1304 at gmail.com>

In current implementation, we used ARM-specific flag, that is,
VM_ARM_STATIC_MAPPING, for distinguishing ARM specific static mapped area.
The purpose of static mapped area is to re-use static mapped area when
entire physical address range of the ioremap request can be covered
by this area.

This implementation causes needless overhead for some cases.
For example, assume that there is only one static mapped area and
vmlist has 300 areas. Every time we call ioremap, we check 300 areas for
deciding whether it is matched or not. Moreover, even if there is
no static mapped area and vmlist has 300 areas, every time we call
ioremap, we check 300 areas in now.

If we construct a extra list for static mapped area, we can eliminate
above mentioned overhead.
With a extra list, if there is one static mapped area,
we just check only one area and proceed next operation quickly.

In fact, it is not a critical problem, because ioremap is not frequently
used. But reducing overhead is better idea.

Another reason for doing this work is for removing architecture dependency
on vmalloc layer. I think that vmlist and vmlist_lock is internal data
structure for vmalloc layer. Some codes for debugging and stat inevitably
use vmlist and vmlist_lock. But it is preferable that they are used
as least as possible in outside of vmalloc.c

Now, I introduce an ARM-specific infrastructure for static mapped area. In
the following patch, we will use this and resolve above mentioned problem.

Signed-off-by: Joonsoo Kim <js1304 at gmail.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim at lge.com>

diff --git a/arch/arm/include/asm/mach/static_vm.h b/arch/arm/include/asm/mach/static_vm.h
new file mode 100644
index 0000000..72c8339
--- /dev/null
+++ b/arch/arm/include/asm/mach/static_vm.h
@@ -0,0 +1,45 @@
+/*
+ * arch/arm/include/asm/mach/static_vm.h
+ *
+ * Copyright (C) 2012 LG Electronics, Joonsoo Kim <iamjoonsoo.kim at lge.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _ASM_MACH_STATIC_VM_H
+#define _ASM_MACH_STATIC_VM_H
+
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+
+struct static_vm {
+	struct static_vm	*next;
+	void			*vaddr;
+	unsigned long		size;
+	unsigned long		flags;
+	phys_addr_t		paddr;
+	const void		*caller;
+};
+
+extern struct static_vm *static_vmlist;
+extern spinlock_t static_vmlist_lock;
+
+extern struct static_vm *find_static_vm_paddr(phys_addr_t paddr,
+			size_t size, unsigned long flags);
+extern struct static_vm *find_static_vm_vaddr(void *vaddr);
+extern void init_static_vm(struct static_vm *static_vm,
+			struct vm_struct *vm, unsigned long flags);
+extern void insert_static_vm(struct static_vm *vm);
+
+#endif /* _ASM_MACH_STATIC_VM_H */
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 4e333fa..57b329a 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -6,7 +6,7 @@ obj-y				:= dma-mapping.o extable.o fault.o init.o \
 				   iomap.o
 
 obj-$(CONFIG_MMU)		+= fault-armv.o flush.o idmap.o ioremap.o \
-				   mmap.o pgd.o mmu.o
+				   mmap.o pgd.o mmu.o static_vm.o
 
 ifneq ($(CONFIG_MMU),y)
 obj-y				+= nommu.o
diff --git a/arch/arm/mm/static_vm.c b/arch/arm/mm/static_vm.c
new file mode 100644
index 0000000..265d8e9
--- /dev/null
+++ b/arch/arm/mm/static_vm.c
@@ -0,0 +1,94 @@
+/*
+ * arch/arm/mm/static_vm.c
+ *
+ * Copyright (C) 2012 LG Electronics, Joonsoo Kim <iamjoonsoo.kim at lge.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/spinlock.h>
+
+#include <asm/mach/static_vm.h>
+
+struct static_vm *static_vmlist;
+DEFINE_SPINLOCK(static_vmlist_lock);
+
+struct static_vm *find_static_vm_paddr(phys_addr_t paddr,
+			size_t size, unsigned long flags)
+{
+	struct static_vm *area;
+
+	spin_lock(&static_vmlist_lock);
+	for (area = static_vmlist; area; area = area->next) {
+		if ((area->flags & flags) != flags)
+			continue;
+
+		if (area->paddr > paddr ||
+			paddr + size - 1 > area->paddr + area->size - 1)
+			continue;
+
+		spin_unlock(&static_vmlist_lock);
+		return area;
+	}
+	spin_unlock(&static_vmlist_lock);
+
+	return NULL;
+}
+
+struct static_vm *find_static_vm_vaddr(void *vaddr)
+{
+	struct static_vm *area;
+
+	spin_lock(&static_vmlist_lock);
+	for (area = static_vmlist; area; area = area->next) {
+		/* static_vmlist is ascending order */
+		if (area->vaddr > vaddr)
+			break;
+
+		if (area->vaddr <= vaddr && area->vaddr + area->size > vaddr) {
+			spin_unlock(&static_vmlist_lock);
+			return area;
+		}
+	}
+	spin_unlock(&static_vmlist_lock);
+
+	return NULL;
+}
+
+void init_static_vm(struct static_vm *static_vm,
+				struct vm_struct *vm, unsigned long flags)
+{
+	static_vm->vaddr = vm->addr;
+	static_vm->size = vm->size;
+	static_vm->paddr = vm->phys_addr;
+	static_vm->caller = vm->caller;
+	static_vm->flags = flags;
+}
+
+void insert_static_vm(struct static_vm *vm)
+{
+	struct static_vm *tmp, **p;
+
+	spin_lock(&static_vmlist_lock);
+	for (p = &static_vmlist; (tmp = *p) != NULL; p = &tmp->next) {
+		if (tmp->vaddr >= vm->vaddr) {
+			BUG_ON(tmp->vaddr < vm->vaddr + vm->size);
+			break;
+		} else
+			BUG_ON(tmp->vaddr + tmp->size > vm->vaddr);
+	}
+	vm->next = *p;
+	*p = vm;
+	spin_unlock(&static_vmlist_lock);
+}
-- 
1.7.9.5