Linux 5.10 Graphics Driver Changes From AMDGPU DC For GCN 1.0 To Continuing RDNA 2 Push

[bridgman]

You can still use amdgpu without DC, no?

IIRC you can for anything up to Polaris, ie not Vega or newer.

[illwieckz]

I understand very little bit about this but if you're not using a VGA analog connection can you change the default driver being used to the new one and expect performance gains?

Not necessarily performance gains, but you get the ability to run Vulkan apps.

And OpenCL apps with the amdgpu-pro OpenCL stack running on your distro's own amdgpu driver, which is, as far as I know, the only way to run OpenCL apps with image support on pre-GCN 3 hardware.

[andrei_me]

bridgman is there any mentoring or something like gsoc/evoc/help for an independent developer with no driver experience migrate/develop what is needed to implement VGA support?


E.g: walkthrough like
Git clone this and that
Check radeon code files X, Y, Z
Rewrite that for amdgpu
Run the tests
Create a patch
Send it to mailing list

[agd5f]

bridgman is there any mentoring or something like gsoc/evoc/help for an independent developer with no driver experience migrate/develop what is needed to implement VGA support?


E.g: walkthrough like
Git clone this and that
Check radeon code files X, Y, Z
Rewrite that for amdgpu
Run the tests
Create a patch
Send it to mailing list

Look at the DAC code the non-DC code in amdgpu (dce_v6_0.c) and port it to DC. For DC, you'll need to add an analog encoder type for the DAC. Older versions of DC had some remnants of DAC support which could possibly be salvaged.

[maurossi]

Some additional info on VGA connector topic that were provided by AMD developers (thanks)

SI (DCE6: Tahiti, pitcairn, verde, oland) and CIK (DCE8) had an on die DAC on some parts (Bonaire, kabini, mullins). Some other DCE8 parts (Kaveri) did not, and they used a DP to DAC translator chip called NUTMEG. See the display hardware section of this page for details:

https://www.x.org/wiki/RadeonFeature/

The radeon driver has code for the DACs and NUTMEG chip.

Older versions of DAL that were never upstreamed may have had DAC support.

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal/dc?h=drm-next-4.6-wip-dal-raw

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal?h=amd-staging

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal?h=amd-15.31

How to search the specific commits:

git log --grep VGA -- drivers/gpu/drm/amd/dal
git log --
drivers/gpu/drm/amd/dal/encoder/analog_encoder.c

[Guest]

Some additional info on VGA connector topic that were provided by AMD developers (thanks)

SI (DCE6: Tahiti, pitcairn, verde, oland) and CIK (DCE8) had an on die DAC on some parts (Bonaire, kabini, mullins). Some other DCE8 parts (Kaveri) did not, and they used a DP to DAC translator chip called NUTMEG. See the display hardware section of this page for details:

https://www.x.org/wiki/RadeonFeature/

The radeon driver has code for the DACs and NUTMEG chip.

Older versions of DAL that were never upstreamed may have had DAC support.

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal/dc?h=drm-next-4.6-wip-dal-raw

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal?h=amd-staging

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/dal?h=amd-15.31

How to search the specific commits:

git log --grep VGA -- drivers/gpu/drm/amd/dal
git log --
drivers/gpu/drm/amd/dal/encoder/analog_encoder.c

Ah Nutmeg. That delicious spice that caused suspend/resume headaches with my Llano/Sumo APU (too many codenames, forgot what means what).