amd64_edac: Fix K8 revD and later chip select sizes
Fix DRAM chip select sizes calculation for K8, revisions D and E.
Reported-by: Niklas Söderlund <niklas.soderlund@ericsson.com
Link: http://lkml.kernel.org/r/1320849178-23340-1-git-send-email-niklas.soderlund@ericsson.com
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index b9424dc..0380728 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -1132,12 +1132,36 @@
return ddr2_cs_size(cs_mode, dclr & WIDTH_128);
}
else if (pvt->ext_model >= K8_REV_D) {
+ unsigned diff;
WARN_ON(cs_mode > 10);
- if (cs_mode == 3 || cs_mode == 8)
- return 32 << (cs_mode - 1);
- else
- return 32 << cs_mode;
+ /*
+ * the below calculation, besides trying to win an obfuscated C
+ * contest, maps cs_mode values to DIMM chip select sizes. The
+ * mappings are:
+ *
+ * cs_mode CS size (mb)
+ * ======= ============
+ * 0 32
+ * 1 64
+ * 2 128
+ * 3 128
+ * 4 256
+ * 5 512
+ * 6 256
+ * 7 512
+ * 8 1024
+ * 9 1024
+ * 10 2048
+ *
+ * Basically, it calculates a value with which to shift the
+ * smallest CS size of 32MB.
+ *
+ * ddr[23]_cs_size have a similar purpose.
+ */
+ diff = cs_mode/3 + (unsigned)(cs_mode > 5);
+
+ return 32 << (cs_mode - diff);
}
else {
WARN_ON(cs_mode > 6);