powerpc/pseries: Use base address to derive starting page frame number

Use the base address of the lmb to derive the starting page frame number
instead of trying to extract it from the drc index of the lmb.  The drc
index should not be used for this as it will, and did, break.

Until this point, systems that have had memory represented in the device
tree with a node for each lmb the drc index would (luckily) closely
track the base address of the lmb.  For example a lmb with a drc index
of 8000000a would have a base address of a0000000.  This correlation
allowed the current code to derive the starting page frame number from
the drc inddex

Device tree layouts where lmbs are represented under the
ibm,dynamic-reconfiguration-memory node in the ibm,dynamic-memory
property do not have this correlation between the drc index and base
address of the lmb.
Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/pseries/hotplug-memory.c

@@ -18,8 +18,9 @@
 static int pseries_remove_memory(struct device_node *np)
 {
 	const char *type;
-	const unsigned int *my_index;
 	const unsigned int *regs;
+	unsigned long base;
+	unsigned int lmb_size;
 	u64 start_pfn, start;
 	struct zone *zone;
 	int ret = -EINVAL;
@@ -32,17 +33,16 @@ static int pseries_remove_memory(struct device_node *np)
 		return 0;
 
 	/*
-	 * Find the memory index and size of the removing section
+	 * Find the bae address and size of the lmb
 	 */
-	my_index = of_get_property(np, "ibm,my-drc-index", NULL);
-	if (!my_index)
-		return ret;
-
 	regs = of_get_property(np, "reg", NULL);
 	if (!regs)
 		return ret;
 
-	start_pfn = section_nr_to_pfn(*my_index & 0xffff);
+	base = *(unsigned long *)regs;
+	lmb_size = regs[3];
+
+	start_pfn = base >> PFN_SECTION_SHIFT;
 	zone = page_zone(pfn_to_page(start_pfn));
 
 	/*
@@ -54,28 +54,29 @@ static int pseries_remove_memory(struct device_node *np)
 	 * to sysfs "state" file and we can't remove sysfs entries
 	 * while writing to it. So we have to defer it to here.
 	 */
-	ret = __remove_pages(zone, start_pfn, regs[3] >> PAGE_SHIFT);
+	ret = __remove_pages(zone, start_pfn, lmb_size >> PAGE_SHIFT);
 	if (ret)
 		return ret;
 
 	/*
 	 * Update memory regions for memory remove
 	 */
-	lmb_remove(start_pfn << PAGE_SHIFT, regs[3]);
+	lmb_remove(base, lmb_size);
 
 	/*
 	 * Remove htab bolted mappings for this section of memory
 	 */
-	start = (unsigned long)__va(start_pfn << PAGE_SHIFT);
-	ret = remove_section_mapping(start, start + regs[3]);
+	start = (unsigned long)__va(base);
+	ret = remove_section_mapping(start, start + lmb_size);
 	return ret;
 }
 
 static int pseries_add_memory(struct device_node *np)
 {
 	const char *type;
-	const unsigned int *my_index;
 	const unsigned int *regs;
+	unsigned long base;
+	unsigned int lmb_size;
 	u64 start_pfn;
 	int ret = -EINVAL;
 
@@ -87,22 +88,19 @@ static int pseries_add_memory(struct device_node *np)
 		return 0;
 
 	/*
-	 * Find the memory index and size of the added section
+	 * Find the base and size of the lmb
 	 */
-	my_index = of_get_property(np, "ibm,my-drc-index", NULL);
-	if (!my_index)
-		return ret;
-
 	regs = of_get_property(np, "reg", NULL);
 	if (!regs)
 		return ret;
 
-	start_pfn = section_nr_to_pfn(*my_index & 0xffff);
+	base = *(unsigned long *)regs;
+	lmb_size = regs[3];
 
 	/*
 	 * Update memory region to represent the memory add
 	 */
-	lmb_add(start_pfn << PAGE_SHIFT, regs[3]);
+	lmb_add(base, lmb_size);
 	return 0;
 }