powerpc: respect mem= setting for early memory limit setup

For those MMUs that have some form of bolt'd linear mapping (TLB)
required its rare that one ever sets mem= smaller than the size of that
mapping.

However, on Book-E 64 parts the initial linear mapping is quite large
(1G) so its quite reasonable that mem= is set smaller than that.

We need to parse the command line for mem= limit and constrain the
amount of memory we map initially by it if need be.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 831a201e03d2..8ad825c063c4 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -737,12 +737,15 @@ void __init early_init_devtree(void *params)
 
         of_scan_flat_dt(early_init_dt_scan_root, NULL);
         of_scan_flat_dt(early_init_dt_scan_memory_ppc, NULL);
-        setup_initial_memory_limit(memstart_addr, first_memblock_size);
 
         /* Save command line for /proc/cmdline and then parse parameters */
         strlcpy(boot_command_line, cmd_line, COMMAND_LINE_SIZE);
         parse_early_param();
 
+        /* make sure we've parsed cmdline for mem= before this */
+        if (memory_limit)
+                first_memblock_size = min(first_memblock_size, memory_limit);
+        setup_initial_memory_limit(memstart_addr, first_memblock_size);
         /* Reserve MEMBLOCK regions used by kernel, initrd, dt, etc... */
         memblock_reserve(PHYSICAL_START, __pa(klimit) - PHYSICAL_START);
         /* If relocatable, reserve first 32k for interrupt vectors etc. */