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

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

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?

> > 24-bit works on my G200HE and G200 test machines. Maybe the G200ER has a bug.
> >
> > When I try 16-bit depth, the display works, but is way too dark. No fiddling with the LUT tables fixes this. It's 90s hardware, so it should support 16-bit framebuffers well, but there's no obvious bug to be seen.
> >
> > I guess, we could remove 16 and 24 bit support for now if nothing else helps.
>
>
> maybe better if we revert 73f54d5d9682 (drm/mgag200: Remove special case
> for G200SE with <2 MiB)
>
> because there is no test result on device G200_SE

We cannot revert it directly, but tomorrow I'll send you a patch that 
should restore the old behavior.

Best regards
Thomas

> static unsigned int mgag200_preferred_depth(struct mga_device *mdev)
> {
>         if (IS_G200_SE(mdev) && mdev->vram_fb_available < (2048*1024))
>                 return 16;
>         else
>                 return 32;
> }
>
> Best Regards
> Wang Yugui (wangyugui@xxxxxxxxxxxx)
> 2022/09/14

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

Attachment: OpenPGP_signature
Description: OpenPGP digital signature