m68k: Enable memtest functionality

Enable the memtest functionality and rearrange some code to prevent it
from clobbering the initrd.

The code to implement CONFIG_BLK_DEV_INITRD was conditional on
!defined(CONFIG_SUN3). For simplicity, remove that test on the basis
that m68k_ramdisk.size == 0 on Sun 3. The SLIME source code at
http://sammy.net/sun3/ftp/pub/m68k/sun3/slime/slime-2.0.tar.gz
indicates that no BI_RAMDISK entry is ever passed to the kernel due
to #ifdef 0 around the relevant code.

Cc: Mike Rapoport <rppt@kernel.org>
Cc: Sam Creasey <sammy@sammy.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/8170fe1d1c62426d82275d36ba409ecc18754292.1637274578.git.fthain@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -2934,7 +2934,7 @@
 			both parameters are enabled, hugetlb_free_vmemmap takes
 			precedence over memory_hotplug.memmap_on_memory.
 
-	memtest=	[KNL,X86,ARM,PPC,RISCV] Enable memtest
+	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
 			Format: <integer>
 			default : 0 <disable>
 			Specifies the number of memtest passes to be

arch/m68k/Kconfig

@@ -9,6 +9,7 @@ config M68K
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
 	select ARCH_NO_PREEMPT if !COLDFIRE
+	select ARCH_USE_MEMTEST if MMU_MOTOROLA
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
 	select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE

arch/m68k/kernel/setup_mm.c

@@ -338,13 +338,6 @@ void __init setup_arch(char **cmdline_p)
 		panic("No configuration setup");
 	}
 
-	paging_init();
-
-#ifdef CONFIG_NATFEAT
-	nf_init();
-#endif
-
-#ifndef CONFIG_SUN3
 #ifdef CONFIG_BLK_DEV_INITRD
 	if (m68k_ramdisk.size) {
 		memblock_reserve(m68k_ramdisk.addr, m68k_ramdisk.size);
@@ -354,6 +347,12 @@ void __init setup_arch(char **cmdline_p)
 	}
 #endif
 
+	paging_init();
+
+#ifdef CONFIG_NATFEAT
+	nf_init();
+#endif
+
 #ifdef CONFIG_ATARI
 	if (MACH_IS_ATARI)
 		atari_stram_reserve_pages((void *)availmem);
@@ -364,8 +363,6 @@ void __init setup_arch(char **cmdline_p)
 	}
 #endif
 
-#endif /* !CONFIG_SUN3 */
-
 /* set ISA defs early as possible */
 #if defined(CONFIG_ISA) && defined(MULTI_ISA)
 	if (MACH_IS_Q40) {

arch/m68k/mm/motorola.c

@@ -457,6 +457,8 @@ void __init paging_init(void)
 
 	flush_tlb_all();
 
+	early_memtest(min_addr, max_addr);
+
 	/*
 	 * initialize the bad page table and bad page to point
 	 * to a couple of allocated pages