[Nouveau] "Stuttering" display, NVA0 chipset.

[Sam Varshavchik]

I'm running xorg-x11-drv-nouveau-1.0.9-1.fc19.x86_64 and xorg-x11-server- 
Xorg-1.14.2-9.fc19.x86_64

On the following chipset, the display suffers from "stuttering":

06:00.0 VGA compatible controller: NVIDIA Corporation GT200b [GeForce GTX  
285] (rev a1) (prog-if 00 [VGA controller])
        Subsystem: Gigabyte Technology Co., Ltd Device 34c9
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+  
Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-  
<TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 256 bytes
        Interrupt: pin A routed to IRQ 24
        Region 0: Memory at f7000000 (32-bit, non-prefetchable) [size=16M]
        Region 1: Memory at d0000000 (64-bit, prefetchable) [size=256M]
        Region 3: Memory at f8000000 (64-bit, non-prefetchable) [size=32M]
        Region 5: I/O ports at dc00 [size=128]
        Expansion ROM at f6f80000 [disabled] [size=512K]
        Capabilities: <access denied>
        Kernel driver in use: nouveau

[   531.742] (--) NOUVEAU(0): Chipset: "NVIDIA NVA0"

By "stutters" I mean that at random intervals, at least several times a  
minute, the entire display completely freezes, for an interval ranging  
between about quarter of a second, to sometimes as long as 5-6 seconds.

By "freezes" I mean that it just stops updating. No artifacts, just a frozen  
display.

When the display eventually becomes unstuck, it's completely up to date.  
Everything that should be rendered, to that point, is rendered. It's as if  
the framebuffer continues to get updated normally, but the display is not  
being refreshed. Except for the mouse pointer! When the display is not  
refreshing, the mouse pointer continues to be responsive.

Basically, if I'm playing some video, the audio keeps going, the video stops  
for 1-6 seconds, then continues running, synchronized with the audio. Or, if  
I'm typing something on the terminal, after the display unsticks itself,  
everything that was typed in the interim, is where it should be. That's the  
best way I can describe it.

I see no complaints in /var/log/messages, nor in Xorg.0.log

I have the same kernel, nouveau, and Xorg version running on different  
hardware with an NVC1 chipset, no issues there. That display is smooth as  
butter.

I'm fairly certain that this is a recent regression. I've had this hardware  
for at least three years, and this problem is fairly recent. Can't quite  
recall at which kernel/Xorg/nouveau version this started happening.

I don't think it's a bad DVI cable. If I drop out of X, and to som work on  
the console terminal (VESA framebuffer display only), the display does not  
appear to stutter at all.

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