ARM: SMP: use idmap_pgd for mapping MMU enable during secondary booting

The ARM SMP booting code allocates a temporary set of page tables
containing an identity mapping of the kernel image and provides this
to secondary CPUs for initial booting.

In reality, we only need to include the __turn_mmu_on function in the
identity mapping since the rest of the kernel is executing from virtual
addresses after this point.

This patch adds __turn_mmu_on to the .idmap.text section, allowing the
SMP booting code to use the idmap_pgd directly and not have to populate
its own set of page table.

As a result of this patch, we can make the identity_mapping_add function
static (since it is only used within mm/idmap.c) and also remove the
identity_mapping_del function. The identity map population is moved to
an early initcall so that it is setup in time for secondary CPU bringup.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm/mm/idmap.c

@@ -32,7 +32,7 @@ static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
 	} while (pud++, addr = next, addr != end);
 }
 
-void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
+static void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
 {
 	unsigned long prot, next;
 
@@ -47,36 +47,6 @@ void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
 	} while (pgd++, addr = next, addr != end);
 }
 
-#ifdef CONFIG_SMP
-static void idmap_del_pmd(pud_t *pud, unsigned long addr, unsigned long end)
-{
-	pmd_t *pmd = pmd_offset(pud, addr);
-	pmd_clear(pmd);
-}
-
-static void idmap_del_pud(pgd_t *pgd, unsigned long addr, unsigned long end)
-{
-	pud_t *pud = pud_offset(pgd, addr);
-	unsigned long next;
-
-	do {
-		next = pud_addr_end(addr, end);
-		idmap_del_pmd(pud, addr, next);
-	} while (pud++, addr = next, addr != end);
-}
-
-void identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)
-{
-	unsigned long next;
-
-	pgd += pgd_index(addr);
-	do {
-		next = pgd_addr_end(addr, end);
-		idmap_del_pud(pgd, addr, next);
-	} while (pgd++, addr = next, addr != end);
-}
-#endif
-
 extern char  __idmap_text_start[], __idmap_text_end[];
 
 static int __init init_static_idmap(void)
@@ -97,7 +67,7 @@ static int __init init_static_idmap(void)
 
 	return 0;
 }
-arch_initcall(init_static_idmap);
+early_initcall(init_static_idmap);
 
 /*
  * In order to soft-boot, we need to switch to a 1:1 mapping for the