[MIPS] FLATMEM: introduce PHYS_OFFSET.

The old code was assuming that min_low_pfn was always 0. This
means that platforms having a big hole at their memory start
paid the price of wasting some memory for the allocation of
unused entries in mem_map[].

This patch prevents this waste.

It introduces PHYS_OFFSET define which is the start of the
physical memory and uses it wherever needed. Specially when
converting physical/virtual addresses into virtual/physical
ones.

Currently all platforms defines PHYS_OFFSET to 0.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index f352cd9c834b..e1d76b87601c 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -315,13 +315,17 @@ static void __init bootmem_init(void)
 
         if (min_low_pfn >= max_low_pfn)
                 panic("Incorrect memory mapping !!!");
-        if (min_low_pfn > 0) {
+        if (min_low_pfn > ARCH_PFN_OFFSET) {
                 printk(KERN_INFO
                        "Wasting %lu bytes for tracking %lu unused pages\n",
-                       min_low_pfn * sizeof(struct page),
-                       min_low_pfn);
-                min_low_pfn = 0;
+                       (min_low_pfn - ARCH_PFN_OFFSET) * sizeof(struct page),
+                       min_low_pfn - ARCH_PFN_OFFSET);
+        } else if (min_low_pfn < ARCH_PFN_OFFSET) {
+                printk(KERN_INFO
+                       "%lu free pages won't be used\n",
+                       ARCH_PFN_OFFSET - min_low_pfn);
         }
+        min_low_pfn = ARCH_PFN_OFFSET;
 
         /*
          * Determine low and high memory ranges