From: mikem@beardog.cca.cpqcorp.net
This patch addresses a bug in the ASIC on the 6400 series controllers. When
prefetching from host memory we grab an extra 750 or so bytes of data. If
this occurs on a memory boundary the machine will MCA. This bug affects IPF
and Alpha based platforms. It is not known to be a problem on x86.
Prefetch will be disabled via the f/w. We need to enable it on x86 to
address a _big_ performance hit on RAID 1 operations.
It is in the 2.4 tree.
---
drivers/block/cciss.c | 11 +++++++++++
drivers/block/cciss_cmd.h | 1 +
2 files changed, 12 insertions(+)
diff -puN drivers/block/cciss.c~cciss-05-ASIC-bug-workaround drivers/block/cciss.c
--- 25/drivers/block/cciss.c~cciss-05-ASIC-bug-workaround 2004-02-04 20:21:45.000000000 -0800
+++ 25-akpm/drivers/block/cciss.c 2004-02-04 20:21:45.000000000 -0800
@@ -2277,6 +2277,17 @@ static int cciss_pci_init(ctlr_info_t *c
printk("Does not appear to be a valid CISS config table\n");
return -1;
}
+
+#ifdef CONFIG_X86
+{
+ /* Need to enable prefetch in the SCSI core for 6400 in x86 */
+ __u32 prefetch;
+ prefetch = readl(&(c->cfgtable->SCSI_Prefetch));
+ prefetch |= 0x100;
+ writel(prefetch, &(c->cfgtable->SCSI_Prefetch));
+}
+#endif
+
#ifdef CCISS_DEBUG
printk("Trying to put board into Simple mode\n");
#endif /* CCISS_DEBUG */
diff -puN drivers/block/cciss_cmd.h~cciss-05-ASIC-bug-workaround drivers/block/cciss_cmd.h
--- 25/drivers/block/cciss_cmd.h~cciss-05-ASIC-bug-workaround 2004-02-04 20:21:45.000000000 -0800
+++ 25-akpm/drivers/block/cciss_cmd.h 2004-02-04 20:21:45.000000000 -0800
@@ -265,6 +265,7 @@ typedef struct _CfgTable_struct {
DWORD Reserved;
BYTE ServerName[16];
DWORD HeartBeat;
+ DWORD SCSI_Prefetch;
} CfgTable_struct;
#pragma pack()
#endif // CCISS_CMD_H
_