[PATCH] MIPS: fix memory reservation for non-usermem setups

[Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>]

From: Tobias Wolf <dev-NTEO@vplace.de>

Commit 67a3ba25aa95 ("MIPS: Fix incorrect mem=X@Y handling") introduced a new
issue for rt288x where "PHYS_OFFSET" is 0x0 but the calculated "ramstart" is
not. As the prerequisite of custom memory map has been removed, this results
in the full memory range of 0x0 - 0x8000000 to be marked as reserved for this
platform.

This patch adds the originally intended prerequisite again.

This patch has been present in OpenWrt tree for over 2 years:
https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=93bfafb8dc209f153022796d9e747149e66cc29e

Fixes: 67a3ba25aa95 ("MIPS: Fix incorrect mem=X@Y handling")
Signed-off-by: Tobias Wolf <dev-NTEO@vplace.de>
[Reword commit message]
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
Cc: Marcin Nowakowski <marcin.nowakowski@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
---
 arch/mips/kernel/setup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 279be0153f8b..97e3a0db651b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -251,6 +251,8 @@ static unsigned long __init init_initrd(void)
  * Initialize the bootmem allocator. It also setup initrd related data
  * if needed.
  */
+static int usermem __initdata;
+
 #if defined(CONFIG_SGI_IP27) || (defined(CONFIG_CPU_LOONGSON64) && defined(CONFIG_NUMA))
 
 static void __init bootmem_init(void)
@@ -290,7 +292,7 @@ static void __init bootmem_init(void)
 	/*
 	 * Reserve any memory between the start of RAM and PHYS_OFFSET
 	 */
-	if (ramstart > PHYS_OFFSET)
+	if (usermem && ramstart > PHYS_OFFSET)
 		memblock_reserve(PHYS_OFFSET, ramstart - PHYS_OFFSET);
 
 	if (PFN_UP(ramstart) > ARCH_PFN_OFFSET) {
@@ -338,8 +340,6 @@ static void __init bootmem_init(void)
 
 #endif	/* CONFIG_SGI_IP27 */
 
-static int usermem __initdata;
-
 static int __init early_parse_mem(char *p)
 {
 	phys_addr_t start, size;
-- 
2.30.1