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

[Thomas Zimmermann]

(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.

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.

Best regards
Thomas

> 
> kernel 5.19.3 & video=1024x768-32
> 	dell/T620/centos-8.5	OK
> 	dell/T630/centos-7.9	OK



> 
> Both DELL/T620 and DELL/T630 have the lastest BIOS/iDRAC installed.
> 
> Best Regards
> Wang Yugui (wangyugui at e16-tech.com)
> 2022/09/14
> 
> 
> 
>>
>> Best regards
>> Thomas
>>
>>>
>>> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c
>>> b/drivers/gpu/drm/mgag200/mgag200_mode.c
>>> index 225cca2ed60e..563e3ab05fbc 100644
>>> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
>>> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
>>> @@ -1070,7 +1070,7 @@ int mgag200_modeset_init(struct mga_device *mdev, resource_size_t vram_available
>>>
>>>           dev->mode_config.max_width = MGAG200_MAX_FB_WIDTH;
>>>           dev->mode_config.max_height = MGAG200_MAX_FB_HEIGHT;
>>> -       dev->mode_config.preferred_depth = 24;
>>> +       dev->mode_config.preferred_depth = 32;
>>>           dev->mode_config.fb_base = mdev->vram_res->start;
>>>           dev->mode_config.funcs = &mgag200_mode_config_funcs;
>>>
>>> Best Regards
>>> Wang Yugui (wangyugui at e16-tech.com)
>>> 2022/09/13
>>>
>>>
>>>
>> -- Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Gesch?ftsführer: Ivo Totev
> 
> 

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