Edgar Fuß <[email protected]> writes:

> I'm curious what the TDMS bandwidth limit values in get_tmds_link_bandwidth() 
> are based on.

They're based on what the nvidia proprietary driver itself refuses to
do, though, I'm not 100% sure that I had nv44 in my sample when I made
that change.

> We're using chipset == 44 cards that happily run 1600x1200@60 using the 
> propriety driver and which also used to work with nouveau up to Linux 
> 2.6.36.2. Since 2.6.37, nouveau refuses to use that mode because the required 
> 163M pixel clock exceeds the computed TDMS bandwidth of 155M (earlier 
> versions allowed for 165M regardless of chipset value).
> Although I cannot tell for sure which timing the closed-source driver runs 
> 1600x1200@60 with on these monitors, I find it unlikely that it uses some 
> built-in, non-EDID timing requiring a lower pixel clock. I also don't suspect 
> NVidia running their own chips above specs.

It might be using a reduced-blanking mode, check your Xorg.0.log to be
sure. See the "-logverbose" option if you don't get all the timings
printed out with the default verbosity level.

> So either NVidia doesn't disclose the specs even to their own programmers, 
> the values in get_tmds_link_bandwidth() are wrong, or, more likely, I'm 
> missing something.
> Patching get_tmds_link_bandwidth() to allow for 165M already for chipset >= 
> 0x44 appears to work. However, I don't feel comfortable with stretching rates 
> above spec.
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