[src/netbsd-1-5]: src/share/man/man4 Pull up 1.20->1.21 (approved by thorpej):

[bouyer <bouyer%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1b4fde976d34
branches:  netbsd-1-5
changeset: 488462:1b4fde976d34
user:      bouyer <bouyer%NetBSD.org@localhost>
date:      Fri Jul 07 12:15:42 2000 +0000

description:
Pull up 1.20->1.21 (approved by thorpej):
document the AMD IDE workaround, and how to disable it.

diffstat:

 share/man/man4/pciide.4 |  14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diffs (39 lines):

diff -r 102a34c0e2d1 -r 1b4fde976d34 share/man/man4/pciide.4
--- a/share/man/man4/pciide.4   Fri Jul 07 11:49:14 2000 +0000
+++ b/share/man/man4/pciide.4   Fri Jul 07 12:15:42 2000 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: pciide.4,v 1.19.2.1 2000/06/27 14:59:56 bouyer Exp $
+.\"    $NetBSD: pciide.4,v 1.19.2.2 2000/07/07 12:15:42 bouyer Exp $
 .\"
 .\" Copyright (c) 1998 Manuel Bouyer.
 .\"
@@ -39,6 +39,7 @@
 .Cd "pciide* at pci? dev ? function ? flags 0x0000"
 .Cd "pciide* at pnpbios? index ?"
 .Cd "options PCIIDE_CMD064x_DISABLE"
+.Cd "options PCIIDE_AMD756_ENABLEDMA"
 .Sh DESCRIPTION
 The
 .Nm pciide
@@ -85,11 +86,20 @@
 .Sh BUGS
 There's no way to reliably know if a PCI064x controller is enabled or not.
 If the driver finds a PCI064x, it will assume it is enabled unless the
-PCIIDE_CMD064x_DISABLE is specified in the kernel config file.
+PCIIDE_CMD064x_DISABLE option 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 and uses the ISA legacy I/O ports
 and interrupts.
 .Pp
+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 eventually be disabled on a per-drive
+basis with config flags, see
+.Xr wd 4 .
+The bug, if triggered, will cause a total system hang.
+.Pp
 The timings used for the PIO and DMA modes for controllers listed above
 are for a PCI bus running at 30 or 33 Mhz (except the OPTi controller,
 which supports both 25 and 33 Mhz PCI bus timings). This driver may not