Hi Am 27.07.23 um 23:34 schrieb 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@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.
Thanks for this information. If you configure a screen and/or modes via config file, such as 20-screen.conf, it overrides Xorg's autodetection. So X will happily use whatever you configured. This explains my other mail's question why Xorg even tries 1440x900 at all.
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) ??
There's mode detection, which does the general test with mode_valid. It returns a list with possible modes. And there's mode setting, which tests if the display setting as a whole (mode, color format, outputs, and more) can can be programmed in the given combination. That's what fails with the new driver, but worked with the old driver.
I guess that the configured mode of 1440x900 somehow passed testing in the old driver. And as your chip could handle the overclocked pixelrate settings, you got a stable output even with 32-bit colors.
I assume that the new driver is somehow more strict in testing and rejects the overclocked pixel rate. (But I cannot see that in the code TBH).
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 ?)
I'm not quite sure how to proceed here, as the driver is correct and the problem came from a mismatching config file on your system.
Best regards Thomas
Best wishes, Roger.
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
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