mgag200 broken on kernel-6.0-rc3 on DELL/T620

[Wang Yugui]

Hi,


> Hi
> 
> Am 14.09.22 um 16:58 schrieb Wang Yugui:
> > Hi,
> >
> >> (cc: Jocelyn)
> >>
> >> Hi
> >>
> >> Am 14.09.22 um 10:29 schrieb Wang Yugui:
> >>> Hi,
> >>>
> >>>
> >>>> Hi
> >>>>
> >>>> Am 13.09.22 um 17:15 schrieb Wang Yugui:
> >>>> [...]
> >>>>>>>
> >>>>>>> so I tried to revert patch of mgag200 driver in batch of 2 or 3, the I
> >>>>>>> noticed the patch 'Subject: drm/mgag200: Remove special case for G200SE
> >>>>>>> with <2 MiB' and then tried this dirty fix.
> >>>>>>
> >>>>>> Oh, great work! Thank you. From looking at the screenshot that you provided, it seems as if the 24-bit mode setting is broken. I'm not sure why the G200SE workaround applies to a G200ER, but we'll see.
> >>>>>
> >>>>> I tested 'preferred_depth = 32' too. it works on T630 too.
> >>>>>
> >>>>> so both 16 and 32 work, but 24 failed on DELL/T630.
> >>>>
> >>>> I tried on my test machine with a 5.19 kernel and found that 32-bit and 24-bit pixels work, but 16-bit looks incorrect.
> >>>>
> >>>> What are the results if you boot your kernel 5.19.3 with the parameter video=1024x768-24? This should enable 24-bit pixels.
> >>>>
> >>>> How does video=1024x768-16 look with the 5.19 kernel?
> >>>
> >>> test result here
> >>> kernel 5.19.3 & video=1024x768-24
> >>> 	dell/T620/centos-8.5	broken
> >>> 	dell/T630/centos-7.9	broken
> >>
> >> I assume that Centos 7 and 8 have fairly old kernels? So it's been a long-standing bug.
> >
> > We install kernel 5.19.3/5.15.67 into Centos 7 and 8.
> > default it work well.  broken just when 'video=1024x768-24', so it may
> > not a long-standing bug.
> 
> I don't quite understand. Does 'video=1024x768-24' work with 5.15.67?

kernel 5.15.67 with 'video=1024x768-24' is broken on DELL/T630.

kernel 5.15.67 without 'video=1024x768-24' works well on DELL/T630.

Best Regards
Wang Yugui (wangyugui at e16-tech.com)
2022/09/15