xsrc/47622: nv driver hangs with XAA

[martin%NetBSD.org@localhost]

>Number:         47622
>Category:       xsrc
>Synopsis:       nv driver hangs with XAA
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    xsrc-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Mar 05 09:30:00 +0000 2013
>Originator:     Martin Husemann
>Release:        NetBSD 6.x
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: (not this machine, using amd64 GENERIC from the tip of netbsd-6)
Architecture: x86_64
Machine: amd64
>Description:

Using in-tree Xorg with this graphics card:

vga0 at pci1 dev 0 function 0: vendor 0x10de product 0x0110 (rev. 0xb2)

or as Xorg calls it:

[   517.541] (--) NV(0): Chipset: "GeForce2 MX/MX 400"

leads to quick lockups in the X server.

It hangs in external/mit/xf86-video-nv/dist/src/nv_xaa.c line 287:

void NVSync(ScrnInfoPtr pScrn)
{
    NVPtr pNv = NVPTR(pScrn);
 
    if(pNv->DMAKickoffCallback)
       (*pNv->DMAKickoffCallback)(pScrn);
  
    while(READ_GET(pNv) != pNv->dmaPut);   <<--- 287
 
    while(pNv->PGRAPH[0x0700/4]);
}

and the loop never terminates.

>How-To-Repeat:
Just use X a bit, like fire up a few xterms.

>Fix:
Workaround is to disable all acceleration in /etx/xorg.conf. This works
for me:

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz",
        ### <percent>: "<f>%"
        ### [arg]: arg optional
        #Option     "SWcursor"                  # [<bool>]
        #Option     "HWcursor"                  # [<bool>]
        Option     "NoAccel"   "yes"            # [<bool>]
        #Option     "ShadowFB"                  # [<bool>]
        #Option     "UseFBDev"                  # [<bool>]
        #Option     "Rotate"                    # [<str>]
        #Option     "VideoKey"                  # <i>
        #Option     "FlatPanel"                 # [<bool>]
        #Option     "FPDither"                  # [<bool>]
        #Option     "CrtcNumber"                # <i>
        #Option     "FPScale"                   # [<bool>]
        #Option     "FPTweak"                   # <i>
        #Option     "DualHead"                  # [<bool>]
        Identifier  "Card0"
        Driver      "nv"
        # BusID       "PCI:1:0:0"
EndSection

Side note: note the wrong bus ID generated by Xorg -configure