Prevent probing the secondary channel on CMD646 controllers if the

channel has been disabled by BIOS. This prevents a bus timeout
machine check on B&W G3 PowerMacs, which have a primary-only CMD646
on the motherboard.

Approved by: sos
Obtained from: NetBSD

1 files changed, 6 insertions, 0 deletions

diff --git a/sys/dev/ata/ata-chipset.c b/sys/dev/ata/ata-chipset.c
index 1df8d36..e831fce 100644
--- a/sys/dev/ata/ata-chipset.c
+++ b/sys/dev/ata/ata-chipset.c
@@ -1509,6 +1509,12 @@ ata_sii_chipinit(device_t dev)
     }
     else 
 	ctlr->setmode = ata_cmd_setmode;
+
+    if ((pci_read_config(dev, 0x51, 1) & 0x08) != 0x08) {
+        device_printf(dev, "secondary channel disabled\n");
+        ctlr->channels = 1;
+    }    
+
     return 0;
 }