.Cd "pciide* at pci? flags 0x0000"
.Cd "pciide* at jmb? flags 0x0000"
.Cd "option PCIIDE_AMD756_ENABLEDMA"
.Cd "option PCIIDE_CMD064x_DISABLE"
.Cd "option PCIIDE_CMD0646U_ENABLEUDMA"
.Cd "atapiscsi* at pciide? flags 0x0000"
.Cd "wd* at pciide? flags 0x0000"
DESCRIPTION
The
pciide
driver supports the PCI IDE controllers as specified in the
"PCI IDE controller specification, revision 1.0" draft, as well as the
Serial ATA controllers working either in parallel ATA compatibility mode or
in native serial mode.
It provides the core functions for the
wd(4)
and
atapiscsi(4)
drivers.
This driver includes specific, enhanced support for the CMD Tech
PCI0640 controller and IDE DMA/UltraDMA support for the following PCI IDE
controllers:
Some of these controllers are only available in multifunction PCI chips.
The
0x0001
flag forces the
pciide
driver to use DMA when there is no explicit DMA mode setting support for
the controller but DMA is present.
If the BIOS didn't configure the controller properly, this can
cause a machine hang.
There's no way to know reliably if a CMD064x controller is enabled or not.
If the driver finds a PCI064x, it will assume it is enabled unless
PCIIDE_CMD064x_DISABLE
is specified in the kernel config file.
This will be a problem only if the controller has been disabled in the BIOS
and another controller has been installed which uses the ISA legacy I/O ports
and interrupts.
The CMD0646U is reportedly unable to operate properly in UltraDMA mode.
UltraDMA will not be enabled on this controller unless
PCIIDE_CMD0646U_ENABLEUDMA
is specified in the kernel config file.
For proper operation of UltraDMA 3 and higher modes
a 40-pin, 80-conductor cable must be used.
On some controllers, the
pciide
driver can probe the chip and see if it
detects that an 80-conductor or 40-conductor cable was used.
If not, it will down-grade to UltraDMA 2 mode.
On other controllers, no such capability exists, and the driver assumes
you are using an 80-conductor cable.
If you are getting errors about
corrupted data, check to make sure you are using the correct cable.
An 80-conductor cable is recommended for any IDE installation, not just
ones using faster UltraDMA modes, because it will decrease electrical
noise and increase data reliability.
The AMD756 chip revision D2 has a bug affecting DMA (but not Ultra-DMA)
modes.
The workaround documented by AMD is to not use DMA on any drive which
does not support Ultra-DMA modes.
This does not appear to be necessary on all drives, the
PCIIDE_AMD756_ENABLEDMA option can be used to force multiword DMA
on the buggy revisions.
Multiword DMA can eventually be disabled on a per-drive basis with config
flags, see
wd(4).
The bug, if triggered, will cause a total system hang.
The timings used for the PIO and DMA modes for controllers listed above
are for a PCI bus running at 30 or 33 MHz.
These timings will work on a slower bus,
but they may cause errors on an over-clocked bus.