powerpc/8xx: Remove offset in SPRN_M_TWB

SPRN_M_TWB contains the address of task PGD minus an offset which
compensates the offset required when accessing the kernel PGDIR.
However, since commit ac9f97ff8b32 ("powerpc/8xx: Inconditionally use
task PGDIR in DTLB misses") and commit 33c527522f39 ("powerpc/8xx:
Inconditionally use task PGDIR in ITLB misses") kernel PGDIR is not
used anymore in hot paths.

Remove this offset which was added by
commit fde5a9057fcf ("powerpc/8xx: Optimise access to swapper_pg_dir")

Signed-off-by: Christophe Leroy <[e-mail]>
[maddy: Fixed checkpatch.pl warning for "pathes"]
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/9710d960[e-mail]

arch/powerpc/kernel/head_8xx.S

···
 	INVALIDATE_ADJACENT_PAGES_CPU15(r10, r11)
 	mtspr	SPRN_MD_EPN, r10
 	mfspr	r10, SPRN_M_TWB	/* Get level 1 table */
-	lwz	r11, (swapper_pg_dir-PAGE_OFFSET)@l(r10)	/* Get level 1 entry */
+	lwz	r11, 0(r10)	/* Get level 1 entry */
 	mtspr	SPRN_MD_TWC, r11
 	mfspr	r10, SPRN_MD_TWC
 	lwz	r10, 0(r10)	/* Get the pte */
···
 	 */
 	mfspr	r10, SPRN_MD_EPN
 	mfspr	r10, SPRN_M_TWB	/* Get level 1 table */
-	lwz	r11, (swapper_pg_dir-PAGE_OFFSET)@l(r10)	/* Get level 1 entry */
+	lwz	r11, 0(r10)	/* Get level 1 entry */
 
 	mtspr	SPRN_MD_TWC, r11
 	mfspr	r10, SPRN_MD_TWC
···
 	mfspr	r10, SPRN_DAR
 	mtspr	SPRN_MD_EPN, r10
 	mfspr	r11, SPRN_M_TWB	/* Get level 1 table */
-	lwz	r10, (swapper_pg_dir - PAGE_OFFSET)@l(r11)	/* Get the level 1 entry */
+	lwz	r10, 0(r11)	/* Get the level 1 entry */
 	cmpwi	cr1, r10, 0
 	bne	cr1, 1f
 
···
 	lwz	r10, (swapper_pg_dir - PAGE_OFFSET)@l(r10)	/* Get the level 1 entry */
 	cmpwi	cr1, r10, 0
 	beq	cr1, 1f
-	stw	r10, (swapper_pg_dir - PAGE_OFFSET)@l(r11)	/* Set the level 1 entry */
+	stw	r10, 0(r11)	/* Set the level 1 entry */
 	mfspr	r10, SPRN_M_TW
 	mtcr	r10
 	mfspr	r10, SPRN_SPRG_SCRATCH0
···
 	tophys(r11, r10)
 	mfspr	r11, SPRN_M_TWB	/* Get level 1 table */
 	rlwinm	r11, r11, 0, 20, 31
-	oris	r11, r11, (swapper_pg_dir - PAGE_OFFSET)@ha
+	oris	r11, r11, (swapper_pg_dir - PAGE_OFFSET)@h
+	ori	r11, r11, (swapper_pg_dir - PAGE_OFFSET)@l
 3:
-	lwz	r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)	/* Get the level 1 entry */
+	lwz	r11, 0(r11)	/* Get the level 1 entry */
 	rlwinm	r11, r11, 0, ~_PMD_PAGE_8M
 	mtspr	SPRN_MD_TWC, r11
 	mfspr	r11, SPRN_MD_TWC
···
 	li	r0,0
 	stwu	r0,THREAD_SIZE-STACK_FRAME_MIN_SIZE(r1)
 
-	lis	r6, swapper_pg_dir@ha
+	lis	r6, swapper_pg_dir@h
+	ori	r6, r6, swapper_pg_dir@l
 	tophys(r6,r6)
 	mtspr	SPRN_M_TWB, r6
 

arch/powerpc/mm/nohash/mmu_context.c

···
 static void set_context(unsigned long id, pgd_t *pgd)
 {
 	if (IS_ENABLED(CONFIG_PPC_8xx)) {
-		s16 offset = (s16)(__pa(swapper_pg_dir));
-
-		/*
-		 * Register M_TWB will contain base address of level 1 table minus the
-		 * lower part of the kernel PGDIR base address, so that all accesses to
-		 * level 1 table are done relative to lower part of kernel PGDIR base
-		 * address.
-		 */
-		mtspr(SPRN_M_TWB, __pa(pgd) - offset);
+		mtspr(SPRN_M_TWB, __pa(pgd));
 
 		/* Update context */
 		mtspr(SPRN_M_CASID, id - 1);