1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 6d4c4f227d55..2abe6df9445e 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -4495,6 +4495,7 @@ static __devinit int cciss_kdump_hard_reset_controller(struct pci_dev *pdev)
         int rc, i;
         CfgTable_struct __iomem *cfgtable;
         bool use_doorbell;
+        u32 board_id;
 
         /* For controllers as old a the p600, this is very nearly
          * the same thing as
@@ -4517,6 +4518,19 @@ static __devinit int cciss_kdump_hard_reset_controller(struct pci_dev *pdev)
          * using the doorbell register.
          */
 
+        /* Exclude 640x boards.  These are two pci devices in one slot
+         * which share a battery backed cache module.  One controls the
+         * cache, the other accesses the cache through the one that controls
+         * it.  If we reset the one controlling the cache, the other will
+         * likely not be happy.  Just forbid resetting this conjoined mess.
+         */
+        cciss_lookup_board_id(pdev, &board_id);
+        if (board_id == 0x409C0E11 || board_id == 0x409D0E11) {
+                dev_warn(&pdev->dev, "Cannot reset Smart Array 640x "
+                                "due to shared cache module.");
+                return -ENODEV;
+        }
+
         for (i = 0; i < 32; i++)
                 pci_read_config_word(pdev, 2*i, &saved_config_space[i]);
 
@@ -4600,7 +4614,8 @@ static __devinit int cciss_init_reset_devices(struct pci_dev *pdev)
 
         /* -ENOTSUPP here means we cannot reset the controller
          * but it's already (and still) up and running in
-         * "performant mode".
+         * "performant mode".  Or, it might be 640x, which can't reset
+         * due to concerns about shared bbwc between 6402/6404 pair.
          */
         if (rc == -ENOTSUPP)
                 return 0; /* just try to do the kdump anyhow. */