VIAIDE(4) | Device Drivers Manual | VIAIDE(4) |
viaide
— AMD,
NVIDIA and VIA IDE disk controllers driver
viaide* at pci? dev ? function ? flags
0x0000
options PCIIDE_AMD756_ENABLEDMA
The viaide
driver supports the following
IDE controllers and provides the interface with the hardware for the
ata
driver:
The 0x0002 flag forces the viaide
driver
to disable DMA on chipsets for which DMA would normally be enabled. This can
be used as a debugging aid, or to work around problems where the IDE
controller is wired up to the system incorrectly.
ata(4), atapi(4), intro(4), pci(4), pciide(4), wd(4), wdc(4)
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. This driver may not work properly on overclocked systems.
April 21, 2025 | NetBSD 10.99 |