e752x_edac: provide more info about how DIMMS/ranks are mapped

No funtional changes here. Only the comments got updated.
Reviewed-by: Aristeu Rozanski <arozansk@redhat.com>
Cc: Mark Gross <mark.gross@intel.com>
Cc: Doug Thompson <norsk5@yahoo.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/edac/e752x_edac.c

@@ -4,10 +4,11 @@
  * This file may be distributed under the terms of the
  * GNU General Public License.
  *
- * See "enum e752x_chips" below for supported chipsets
+ * Implement support for the e7520, E7525, e7320 and i3100 memory controllers.
  *
- * Datasheet:
+ * Datasheets:
  *	http://www.intel.in/content/www/in/en/chipsets/e7525-memory-controller-hub-datasheet.html
+ *	ftp://download.intel.com/design/intarch/datashts/31345803.pdf
  *
  * Written by Tom Zimmerman
  *
@@ -16,8 +17,6 @@
  * 	Wang Zhenyu at intel.com
  * 	Dave Jiang at mvista.com
  *
- * $Id: edac_e752x.c,v 1.5.2.11 2005/10/05 00:43:44 dsp_llnl Exp $
- *
  */
 
 #include <linux/module.h>
@@ -190,6 +189,25 @@ enum e752x_chips {
 	I3100 = 3
 };
 
+/*
+ * Those chips Support single-rank and dual-rank memories only.
+ *
+ * On e752x chips, the odd rows are present only on dual-rank memories.
+ * Dividing the rank by two will provide the dimm#
+ *
+ * i3100 MC has a different mapping: it supports only 4 ranks.
+ *
+ * The mapping is (from 1 to n):
+ *	slot	   single-ranked	double-ranked
+ *	dimm #1 -> rank #4		NA
+ *	dimm #2 -> rank #3		NA
+ *	dimm #3 -> rank #2		Ranks 2 and 3
+ *	dimm #4 -> rank $1		Ranks 1 and 4
+ *
+ * FIXME: The current mapping for i3100 considers that it supports up to 8
+ *	  ranks/chanel, but datasheet says that the MC supports only 4 ranks.
+ */
+
 struct e752x_pvt {
 	struct pci_dev *bridge_ck;
 	struct pci_dev *dev_d0f0;