riscv: Move the linear mapping creation in its own function

No change intended, it just splits the linear mapping creation from
setup_vm_final: this prepares for upcoming additions to the linear
mapping creation.

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20230324155421.271544-3-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Alexandre Ghiti

arch/riscv/mm/init.c

@@ -1086,16 +1086,25 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	pt_ops_set_fixmap();
 }
 
-static void __init setup_vm_final(void)
+static void __init create_linear_mapping_range(phys_addr_t start,
+					       phys_addr_t end)
 {
+	phys_addr_t pa;
 	uintptr_t va, map_size;
-	phys_addr_t pa, start, end;
-	u64 i;
 
-	/* Setup swapper PGD for fixmap */
-	create_pgd_mapping(swapper_pg_dir, FIXADDR_START,
-			   __pa_symbol(fixmap_pgd_next),
-			   PGDIR_SIZE, PAGE_TABLE);
+	for (pa = start; pa < end; pa += map_size) {
+		va = (uintptr_t)__va(pa);
+		map_size = best_map_size(pa, end - pa);
+
+		create_pgd_mapping(swapper_pg_dir, va, pa, map_size,
+				   pgprot_from_va(va));
+	}
+}
+
+static void __init create_linear_mapping_page_table(void)
+{
+	phys_addr_t start, end;
+	u64 i;
 
 	/* Map all memory banks in the linear mapping */
 	for_each_mem_range(i, &start, &end) {
@@ -1107,14 +1116,19 @@ static void __init setup_vm_final(void)
 		if (end >= __pa(PAGE_OFFSET) + memory_limit)
 			end = __pa(PAGE_OFFSET) + memory_limit;
 
-		for (pa = start; pa < end; pa += map_size) {
-			va = (uintptr_t)__va(pa);
-			map_size = best_map_size(pa, end - pa);
-
-			create_pgd_mapping(swapper_pg_dir, va, pa, map_size,
-					   pgprot_from_va(va));
-		}
+		create_linear_mapping_range(start, end);
 	}
+}
+
+static void __init setup_vm_final(void)
+{
+	/* Setup swapper PGD for fixmap */
+	create_pgd_mapping(swapper_pg_dir, FIXADDR_START,
+			   __pa_symbol(fixmap_pgd_next),
+			   PGDIR_SIZE, PAGE_TABLE);
+
+	/* Map the linear mapping */
+	create_linear_mapping_page_table();
 
 	/* Map the kernel */
 	if (IS_ENABLED(CONFIG_64BIT))