powerpc/32: Remove the 'nobats' kernel parameter

Mapping without BATs doesn't bring any added value to the user.

Remove that option.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6977314c823cfb728bc0273cea634b41807bfb64.1655202721.git.christophe.leroy@csgroup.eu

Documentation/admin-guide/kernel-parameters.txt

@@ -3495,9 +3495,6 @@
 
 	noautogroup	Disable scheduler automatic task group creation.
 
-	nobats		[PPC] Do not use BATs for mapping kernel lowmem
-			on "Classic" PPC cores.
-
 	nocache		[ARM]
 
 	nodsp		[SH] Disable hardware DSP at boot time.

arch/powerpc/mm/book3s32/mmu.c

@@ -161,7 +161,7 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 	unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
 
 
-	if (debug_pagealloc_enabled_or_kfence() || __map_without_bats) {
+	if (debug_pagealloc_enabled_or_kfence()) {
 		pr_debug_once("Read-Write memory mapped without BATs\n");
 		if (base >= border)
 			return base;

arch/powerpc/mm/init_32.c

@@ -69,12 +69,6 @@ EXPORT_SYMBOL(agp_special_page);
 
 void MMU_init(void);
 
-/*
- * this tells the system to map all of ram with the segregs
- * (i.e. page tables) instead of the bats.
- * -- Cort
- */
-int __map_without_bats;
 int __map_without_ltlbs;
 
 /* max amount of low RAM to map in */
@@ -85,11 +79,6 @@ unsigned long __max_low_memory = MAX_LOW_MEM;
  */
 static void __init MMU_setup(void)
 {
-	/* Check for nobats option (used in mapin_ram). */
-	if (strstr(boot_command_line, "nobats")) {
-		__map_without_bats = 1;
-	}
-
 	if (strstr(boot_command_line, "noltlbs")) {
 		__map_without_ltlbs = 1;
 	}

arch/powerpc/mm/mmu_decl.h

@@ -92,7 +92,6 @@ extern void mapin_ram(void);
 extern void setbat(int index, unsigned long virt, phys_addr_t phys,
 		   unsigned int size, pgprot_t prot);
 
-extern int __map_without_bats;
 extern unsigned int rtas_data, rtas_size;
 
 struct hash_pte;

arch/powerpc/platforms/83xx/misc.c

@@ -121,17 +121,15 @@ void __init mpc83xx_setup_pci(void)
 
 void __init mpc83xx_setup_arch(void)
 {
+	phys_addr_t immrbase = get_immrbase();
+	int immrsize = IS_ALIGNED(immrbase, SZ_2M) ? SZ_2M : SZ_1M;
+	unsigned long va = fix_to_virt(FIX_IMMR_BASE);
+
 	if (ppc_md.progress)
 		ppc_md.progress("mpc83xx_setup_arch()", 0);
 
-	if (!__map_without_bats) {
-		phys_addr_t immrbase = get_immrbase();
-		int immrsize = IS_ALIGNED(immrbase, SZ_2M) ? SZ_2M : SZ_1M;
-		unsigned long va = fix_to_virt(FIX_IMMR_BASE);
-
-		setbat(-1, va, immrbase, immrsize, PAGE_KERNEL_NCG);
-		update_bats();
-	}
+	setbat(-1, va, immrbase, immrsize, PAGE_KERNEL_NCG);
+	update_bats();
 }
 
 int machine_check_83xx(struct pt_regs *regs)