[PATCH] drm/mgag200: Increase bandwidth for G200se A rev1

[Roger Sewell]

Thomas, Jocelyn,

As a result of the collection of the Xorg logs requested by Thomas, I've
realised that at some long-past point upgrade the 1440x900 at 60 mode
disappeared, and in order to get it back I introduced the file
/etc/X11/xorg.conf.d/20-screen.conf attached.

If I remove this file, then with the unmodified new mgag200 module in
place, on going to Settings->Display I am no longer even offered the
1440x900 option - presumably as a result of
mgag200_mode_config_mode_valid returning MODE_BAD.

With this file in place, and with the unmodified new mgag200 module in
place, I am offered this setting, but if I pick it then it is not used
but *is* written into ~/.config/monitors.xml, and then on next login
graphics fail completely.

Hypothesis: there are two different places in the code where mode_valid
is potentially checked, both of which use the mgag200 module, and the
old module only does this check at one of them (deciding which modes to
offer) (which check is bypassed for modes requested in xorg.conf.d),
while the new module does it at both (and hence fails invalid modes
requested in xorg.conf.d) ??

Looking for possible reasons why this might be the case (and straying
way beyond my competence), I note that in the old module
mga_vga_mode_valid is made known to other parts of the system in a
different way than mgag200_mode_config_mode_valid is in the new module
(and indeed they have different parameter types). (Might this be
relevant ?)

Best wishes,
Roger.


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