[RFC][PATCH] powerpc: add usable-memory property to drconf memory

[Chandru <chandru@in.ibm.com>]

kexec-tools in user space collects rtas, crash , tce region ranges 
from /proc/device-tree/ and passes them as linux,usable-memory properties to 
second/kdump kernel in the device tree buffer. With drconf memory in power6 
machines, we need a similar method to preserve those regions in the kdump 
kernel.  This patch adopts a method to append the number 'n' from n'th lmb 
entry in ibm,dynamic-memory as a string to "linux,usable-memory" string , so 
as to distinguish each usable-memory region and it's size.  Another place 
that needs similar change but not included in this patch is in  
arch/powerpc/mm/numa.c. 

Signed-off-by: Chandru S <chandru@in.ibm.com>
---

--- arch/powerpc/kernel/prom.c.orig	2008-06-13 11:42:45.000000000 +0530
+++ arch/powerpc/kernel/prom.c	2008-06-13 12:09:04.000000000 +0530
@@ -884,9 +884,10 @@ static u64 __init dt_mem_next_cell(int s
  */
 static int __init early_init_dt_scan_drconf_memory(unsigned long node)
 {
-	cell_t *dm, *ls;
-	unsigned long l, n, flags;
+	cell_t *dm, *ls, *udm, *reg, *endp;
+	unsigned long l, n, un, flags;
 	u64 base, size, lmb_size;
+	char buf[64], t[8];
 
 	ls = (cell_t *)of_get_flat_dt_prop(node, "ibm,lmb-size", &l);
 	if (ls == NULL || l < dt_root_size_cells * sizeof(cell_t))
@@ -919,6 +920,41 @@ static int __init early_init_dt_scan_drc
 		}
 		lmb_add(base, size);
 	}
+
+	/* Scan usable-memory properties */
+	for (; un != 0; --un) {
+		base = dt_mem_next_cell(dt_root_addr_cells, &udm);
+		flags = dm[3];
+		udm += 4;
+		if ((flags & 0x80) || !(flags & 0x8))
+			continue;
+		strcpy(buf, "linux,usable-memory");
+		sprintf(t, "%d", (int)un);
+		strcat(buf, t);
+		reg = (cell_t *)of_get_flat_dt_prop(node,
+					(const char *)buf, &l);
+		if (reg == NULL)
+			continue;
+		/* remove the previously added lmb */
+		lmb_remove(base, (base+lmb_size));
+		endp = reg + (l / sizeof(cell_t));
+		while ((endp - reg) >= (dt_root_addr_cells +
+						dt_root_size_cells)) {
+
+			base = dt_mem_next_cell(dt_root_addr_cells, &reg);
+			size = dt_mem_next_cell(dt_root_size_cells, &reg);
+
+			if (size == 0)
+				continue;
+			if (iommu_is_off) {
+				if (base >= 0x80000000ul)
+					continue;
+				if ((base + size) > 0x80000000ul)
+					size = 0x80000000ul - base;
+			}
+			lmb_add(base, size);
+		}
+	}
 	lmb_dump_all();
 	return 0;
 }