powerpc/mm: Simplify __set_fixmap()

__set_fixmap() uses __fix_to_virt() then does the boundary checks
by it self. Instead, we can use fix_to_virt() which does the
verification at build time. For this, we need to use it inline
so that GCC can see the real value of idx at buildtime.

In the meantime, we remove the 'fixmaps' variable.
This variable is set but has never been used from the beginning
(commit 2c419bde ("[POWERPC] Port fixmap from x86 and use
for kmap_atomic"))
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/fixmap.h

@@ -17,6 +17,7 @@
 #ifndef __ASSEMBLY__
 #include <linux/kernel.h>
 #include <asm/page.h>
+#include <asm/pgtable.h>
 #ifdef CONFIG_HIGHMEM
 #include <linux/threads.h>
 #include <asm/kmap_types.h>
@@ -62,9 +63,6 @@ enum fixed_addresses {
 	__end_of_fixed_addresses
 };
 
-extern void __set_fixmap (enum fixed_addresses idx,
-					phys_addr_t phys, pgprot_t flags);
-
 #define __FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START		(FIXADDR_TOP - __FIXADDR_SIZE)
 
@@ -72,5 +70,11 @@ extern void __set_fixmap (enum fixed_addresses idx,
 
 #include <asm-generic/fixmap.h>
 
+static inline void __set_fixmap(enum fixed_addresses idx,
+				phys_addr_t phys, pgprot_t flags)
+{
+	map_kernel_page(fix_to_virt(idx), phys, pgprot_val(flags));
+}
+
 #endif /* !__ASSEMBLY__ */
 #endif

arch/powerpc/mm/pgtable_32.c

@@ -408,18 +408,3 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
 	change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 }
 #endif /* CONFIG_DEBUG_PAGEALLOC */
-
-static int fixmaps;
-
-void __set_fixmap (enum fixed_addresses idx, phys_addr_t phys, pgprot_t flags)
-{
-	unsigned long address = __fix_to_virt(idx);
-
-	if (idx >= __end_of_fixed_addresses) {
-		BUG();
-		return;
-	}
-
-	map_kernel_page(address, phys, pgprot_val(flags));
-	fixmaps++;
-}