[PATCH] cciss: disable DMA prefetch on P600

Unconditionally disable DMA prefetch on the P600 controller.  An ASIC bug may
result in prefetching beyond the end of physical memory.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 12 insertions, 0 deletions

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 4899ab27f781..a17223c43aeb 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -3003,6 +3003,17 @@ static int cciss_pci_init(ctlr_info_t *c, struct pci_dev *pdev)
         }
 #endif
 
+        /* Disabling DMA prefetch for the P600
+         * An ASIC bug may result in a prefetch beyond
+         * physical memory.
+         */
+        if(board_id == 0x3225103C) {
+                __u32 dma_prefetch;
+                dma_prefetch = readl(c->vaddr + I2O_DMA1_CFG);
+                dma_prefetch |= 0x8000;
+                writel(dma_prefetch, c->vaddr + I2O_DMA1_CFG);
+        }
+
 #ifdef CCISS_DEBUG
         printk("Trying to put board into Simple mode\n");
 #endif                          /* CCISS_DEBUG */
diff --git a/drivers/block/cciss_cmd.h b/drivers/block/cciss_cmd.h
index 4af7c4c0c7af..b2147cca5acd 100644
--- a/drivers/block/cciss_cmd.h
+++ b/drivers/block/cciss_cmd.h
@@ -55,6 +55,7 @@
 #define I2O_INT_MASK            0x34
 #define I2O_IBPOST_Q            0x40
 #define I2O_OBPOST_Q            0x44
+#define I2O_DMA1_CFG            0x214
 
 //Configuration Table
 #define CFGTBL_ChangeReq        0x00000001l