[PATCH v3 4/6] mm: ioremap: Add arch_ioremap/iounmap()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

Add special hook for architecture to verify or setup addr, size
or prot when ioremap() or iounmap(), which will make the generic
ioremap more useful.

  arch_ioremap() return a pointer,
    - IS_ERR means return an error
    - NULL means continue to remap
    - a non-NULL, non-IS_ERR pointer is directly returned
  arch_iounmap() return a int value,
    - 0 means continue to vunmap
    - error code means skip vunmap and return directly

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 include/asm-generic/io.h | 24 ++++++++++++++++++++++++
 mm/ioremap.c             | 17 ++++++++++++++---
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index e6ffa2519f08..b60f7151e1d6 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -964,6 +964,30 @@ static inline void iounmap(volatile void __iomem *addr)
 #elif defined(CONFIG_GENERIC_IOREMAP)
 #include <linux/pgtable.h>
 
+/*
+ * Arch code can implement the following two special hooks when using GENERIC_IOREMAP
+ * arch_ioremap() return a pointer,
+ *   - IS_ERR means return an error
+ *   - NULL means continue to remap
+ *   - a non-NULL, non-IS_ERR pointer is returned directly
+ * arch_iounmap() return a int,
+ *   - 0 means continue to vunmap
+ *   - error code means skip vunmap and return directly
+ */
+#ifndef arch_ioremap
+static inline void __iomem *arch_ioremap(phys_addr_t phys_addr, size_t size, unsigned long prot)
+{
+	return NULL;
+}
+#endif
+
+#ifndef arch_iounmap
+static inline int arch_iounmap(void __iomem *addr)
+{
+	return 0;
+}
+#endif
+
 void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long prot);
 void iounmap(volatile void __iomem *addr);
 
diff --git a/mm/ioremap.c b/mm/ioremap.c
index 7cb9996b0c12..fac7f23b8c4b 100644
--- a/mm/ioremap.c
+++ b/mm/ioremap.c
@@ -16,6 +16,7 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
 	unsigned long offset, vaddr;
 	phys_addr_t last_addr;
 	struct vm_struct *area;
+	void __iomem *base;
 
 	/* Disallow wrap-around or zero size */
 	last_addr = phys_addr + size - 1;
@@ -27,8 +28,13 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
 	phys_addr -= offset;
 	size = PAGE_ALIGN(size + offset);
 
-	area = get_vm_area_caller(size, VM_IOREMAP,
-			__builtin_return_address(0));
+	base = arch_ioremap(phys_addr, size, prot);
+	if (IS_ERR(base))
+		return NULL;
+	else if (base)
+		return base;
+
+	area = get_vm_area_caller(size, VM_IOREMAP, __builtin_return_address(0));
 	if (!area)
 		return NULL;
 	vaddr = (unsigned long)area->addr;
@@ -45,6 +51,11 @@ EXPORT_SYMBOL(ioremap_prot);
 
 void iounmap(volatile void __iomem *addr)
 {
-	vunmap((void *)((unsigned long)addr & PAGE_MASK));
+	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
+
+	if (arch_iounmap(vaddr))
+		return;
+
+	vunmap(vaddr);
 }
 EXPORT_SYMBOL(iounmap);
-- 
2.35.3