[Assist] HDMI: AMD Ryzen 5 2500U Radeon Vega Mobile Gfx

edgar at openmail.cc edgar at openmail.cc
Mon Apr 15 04:41:55 UTC 2019

I am trying to understand what is important here (as compared to 

> As the upstream Linux driver refuses to load when the nonfree firmware
> is not used, linux-libre's deblob script patches the radeon driver to
> still be able to use it.

I gather that this is informative. It tells me that I am actually using 
the radeon drivers, right?

> While 3D acceleration still doesn't work, it still brings many
> benefits over fallbacks like VESA, such as being able to use the HDMI
> connector, having multi display support, being faster, handling native
> resolutions, etc.

I consider this important. My HDMI connector does not send a signal. Is 
there a way to test if the HDMI port is active? My tests have been 
trying to boot with an HDMI cable which is  connected from the computer 
to screens and flat TV (none of which detect any signal). xrandr does 
not show anything either, even if I boot with the device connected to 
that port.

> Here's an example of how the patching is done in deblob-5.0 for the 
> r600
> class of ATI/AMD GPUs:
>> clean_sed '
>> /r = r600_init_microcode(rdev);/,/}/ s,return r;,/*(DEBLOBBED)*/,
>> ' drivers/gpu/drm/radeon/r600.c 'enable blobless activation'
> I don't remember the exact details, but the code above makes sure that
> the driver doesn't return an error code when the firmware (which is
> called microcode here) cannot be loaded.

This also seems informative, but I would not know how to use it right 
now. Yes, I have seen some messages related to deblobbing in my logs. 
That made me think that the kernel does not work with my HDMI.

> When I worked on it, linux-libre maintainers required me to have
> the change tested on real hardware before enabling it for a given GPU
> family or file (like r600, evergreen, rv770, etc).

That's why I respect developers and appreciate the efforts of having 
free software :) . Thanks!

> So it's probably a matter of:
> - Finding the GPU class you have and understand which file to patch.
> - Downloading linux-libre scripts, which are also available in git[1]
> - Patching them and testing the change
> - Sending the patch to the linux-libre mailing list

Are you suggesting that I do this? (it may be dumb, but it's an actual 

> == Future directions ==
  ---8<--- Snip
>   - The patch enables the driver to load.

All of this looks like a message to someone else or general information 
that may be useful at some point. Is it meant for me?

>   Here what would need to be publicized would be how to blacklist the
>   radeon driver at boot, in the case something goes wrong and the user
>   is left with a black screen during the boot of linux-libre.
>   On Parabola adding "modprobe.blacklist=radeon" to the kernel command
>   line does that at boot. This enables users to easily use the
>   installation medias.
>   This is probably specific to systemd, so it probably doesn't work if
>   you use Parabola without systemd, or if you use GUIX, or Hyperbola,
>   but it may work on Trisquel 8, and PureOS.

I run OpenRC with Parabola. I think that the HDMI hasn't worked with 
Trisquel in the past (I did not try modprobe.blacklist=radeon). Is there 
anything that I need to install in Parabola, Trisquel or PureOS to test? 
Again, how do I test if the HDMI port is active?

>   Once the distribution is installed, users would also need to be able
>   to do again the change in grub to boot and then, once booted to
>   edit /etc/default/grub to add the change permanently.
>   It could also be automatized in some boot script, but that would
>   require more thinking/work.

I agree, and it seems that you are suggesting that I do this when I 
test. I would repeat my question. How do I test the HDMI output from my 

Thank you for your explanation.

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