[PATCH 2/2] drm/radeon/kms: enable underscan option for digital connectors

[Alex Deucher]

2010/8/9 Marius Gröger <marius.groeger at googlemail.com>:
> Am 09.08.2010 09:33, wrote Alex Deucher:
>>
>> 2010/8/9 Marius Gröger<marius.groeger at googlemail.com>:
>>>
>>> Am 08.08.2010 20:09, wrote Alex Deucher:
>>>>
>>>> 2010/8/8 Marius Gröger<marius.groeger at googlemail.com>:
>>>>>
>>>>> Am 08.08.2010 18:22, wrote Alex Deucher:
>>>>>>>
>>>>>>> Also, I kind of was hoping that once I could use 1280x720 for both
>>>>>>> the
>>>>>>> console and the X screen, it would would allow me to switch between
>>>>>>> the
>>>>>>> two
>>>>>>> transparently. Instead, the TV takes notice of the switch and needs
>>>>>>> some
>>>>>>> extra syncing time. Is this expected behaviour?
>>>>>>
>>>>>> You mean switching underscan off and on or a VT switch?  The hw has to
>>>>>> reprogram the mode when it changes the underscan.  As for a VT switch,
>>>>>> it should just be changing the crtc base, but IIRC there was a bug
>>>>>> where X and the console used slightly different modes in some cases.
>>>>>
>>>>> VT switch. I use video=1280x720 at 50 on the command line and select the
>>>>> corresponding EDID resolution within X. Is this bug still pending or is
>>>>> my
>>>>> scenario supposed to work?
>>>>
>>>> You may be seeing this issue:
>>>> http://lists.x.org/archives/xorg-devel/2010-August/011743.html
>>>
>>> "In the absence of the user specifying an overriding monitor
>>> configuration, trust the KMS drivers to have correctly probed the output
>>> modes."
>>>
>>> Well, in my case I *am* specifying an overriding monitor configuration.
>>> Is
>>> there still a chance that video=1280x720 at 50 could be meaning s.th.
>>> different
>>> then the corresponding mode in X that I explicitly choose.
>>
>> Can you verify that the console and X are using the same modeline?
>> The mode selected by video=1280x720 at 50 likely has different timing
>> than the timing used by the mode in X.  Is the VT switch smooth when
>> you don't specify the mode on the console or X (i.e., let the driver
>> decide on it's own)?
>
> Ah ok, "likely has different timing" - this is probably the issue here. I'll
> be investigating this. Is there a way to influence the timing used by
> video=1280x720 at 50 to match the one used in X? Or should I try finding out
> about the console timing and use that as an xorg.conf modeline?

Probably the best bet is to match the X timing to the mode used by the
console.  IIRC, the drm fb code generates the mode using the cvt algo
or something like that.

Alex