Re: Why is mgag200 not used over matroxfb?

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 03.01.23 um 17:20 schrieb Paul Menzel:
> Dear Thomas,
> 
> 
> I have to correct myself.
> 
> 
> Am 16.12.22 um 14:16 schrieb Paul Menzel:
> 
>> Am 16.12.22 um 13:27 schrieb Thomas Zimmermann:
>>
>>> Am 15.12.22 um 17:39 schrieb Paul Menzel:
>>
>> […]
>>
>>>> Between Linux 5.10.103 and 5.10.110/5.15.77, matrixfb fails to load.
>>>
>>> Off-topic, but related. matroxfb is obsolete and there's a maintained 
>>> DRM replacement (mgag200) for this hardware.
>>
>> I also remembered something like this in the back of my head. Though I 
>> thought about using simpledrm (`DRM_SIMPLEDRM`), we do not build though.
>>
>>> Is there anything missing from mgag200 that prevents you from switching?
>> No, it looks like the matroxfb modules take precedence over the 
>> mgag200 module:
>>
>>      $ grep -e FB_MATROX -e MGAG /boot/config-5.15.77.mx64.440
>>      CONFIG_DRM_MGAG200=m
>>      CONFIG_FB_MATROX=m
>>      CONFIG_FB_MATROX_MILLENIUM=y
>>      CONFIG_FB_MATROX_MYSTIQUE=y
>>      CONFIG_FB_MATROX_G=y
>>      CONFIG_FB_MATROX_I2C=m
>>      # CONFIG_FB_MATROX_MAVEN is not set
>>
>>      $ lsmod | grep matrox
>>      matroxfb_base          28672  0
>>      matroxfb_g450          16384  1 matroxfb_base
>>      matroxfb_Ti3026        16384  1 matroxfb_base
>>      matroxfb_accel         16384  1 matroxfb_base
>>      matroxfb_DAC1064       20480  1 matroxfb_base
>>      g450_pll               16384  2 matroxfb_g450,matroxfb_DAC1064
>>      matroxfb_misc          20480  5 
>> g450_pll,matroxfb_Ti3026,matroxfb_base,matroxfb_g450,matroxfb_DAC1064
> 
> The search string was incorrect. The module mgag200, is loaded:
> 
>      $ lsmod | grep mgag200
>      mgag200                36864  0
>      drm_kms_helper        241664  3 mgag200
>      drm                   524288  3 drm_kms_helper,mgag200
>      i2c_algo_bit           16384  1 mgag200
> 
> and it is used according to `lspci`:
> 
>      $ lspci -nn -k -s 09:03.
>      09:03.0 VGA compatible controller [0300]: Matrox Electronics 
> Systems Ltd. MGA G200eW WPCM450 [102b:0532] (rev 0a)
>          DeviceName: Embedded Video
>          Subsystem: Dell MGA G200eW WPCM450 [1028:02d3]
>          Kernel driver in use: mgag200
>          Kernel modules: matroxfb_base, mgag200
> 
> So, it was only a cosmetic issue.

Thanks for all the feedback. The output shown in your original bug 
report came from matroxfb, so it must have been loaded then. I don't 
know what the preferred order is if multiple modules serve the same 
hardware. Maybe it's random.

Best regards
Thomas

> 
> 
> Kind regards,
> 
> Paul

-- 
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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