loongarch: drop definition of PGD_ORDER

This is the order of the page table allocation, not the order of a PGD. 
Since its always hardwired to 0, simply drop it.

[rppt@linux.ibm.com: drop extra BLANK() line in arch/loongarch/kernel/asm-offsets.c]
  Link: https://lkml.kernel.org/r/20220705154708.181258-13-rppt@kernel.org
Link: https://lkml.kernel.org/r/20220703141203.147893-13-rppt@kernel.orgSigned-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Huacai Chen <chenhuacai@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Xuerui Wang <kernel@xen0n.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/loongarch/include/asm/pgtable.h

@@ -21,8 +21,6 @@
 #include <asm-generic/pgtable-nop4d.h>
 #endif
 
-#define PGD_ORDER		0
-
 #if CONFIG_PGTABLE_LEVELS == 2
 #define PGDIR_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT - 3))
 #elif CONFIG_PGTABLE_LEVELS == 3
@@ -43,9 +41,9 @@
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
-#define VA_BITS		(PGDIR_SHIFT + (PAGE_SHIFT + PGD_ORDER - 3))
+#define VA_BITS		(PGDIR_SHIFT + (PAGE_SHIFT - 3))
 
-#define PTRS_PER_PGD	((PAGE_SIZE << PGD_ORDER) >> 3)
+#define PTRS_PER_PGD	(PAGE_SIZE >> 3)
 #if CONFIG_PGTABLE_LEVELS > 3
 #define PTRS_PER_PUD	(PAGE_SIZE >> 3)
 #endif

arch/loongarch/kernel/asm-offsets.c

@@ -190,8 +190,6 @@ void output_mm_defines(void)
 #endif
 	DEFINE(_PTE_T_LOG2, PTE_T_LOG2);
 	BLANK();
-	DEFINE(_PGD_ORDER, PGD_ORDER);
-	BLANK();
 	DEFINE(_PMD_SHIFT, PMD_SHIFT);
 	DEFINE(_PGDIR_SHIFT, PGDIR_SHIFT);
 	BLANK();

arch/loongarch/mm/pgtable.c

@@ -13,7 +13,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 {
 	pgd_t *ret, *init;
 
-	ret = (pgd_t *) __get_free_pages(GFP_KERNEL, PGD_ORDER);
+	ret = (pgd_t *) __get_free_page(GFP_KERNEL);
 	if (ret) {
 		init = pgd_offset(&init_mm, 0UL);
 		pgd_init((unsigned long)ret);