AMD Linux Graphics Driver Preparing For Enabling New LSDMA Ring Mode

[phoronix]

Phoronix: AMD Linux Graphics Driver Preparing For Enabling New LSDMA Ring Mode

Going back to May 2022, AMD Linux graphics driver engineers were working on AMDGPU driver patches to enable a new Light System DMA "LSDMA" IP block. Since then we haven't heard much about LSDMA until some new patches surfaced yesterday for optionally enabling the LSDMA ring mode for the AMDGPU kernel driver...

https://www.phoronix.com/news/AMDGPU-LSDMA-Ring-Mode-Patches

[Kjell]

Does this improve gaming performance?

[DarkFoss]

In a Timothy Leary sort of way.

[agd5f]

Does this improve gaming performance?

No. It may be useful for saving power in certain use cases.

[linuxgeex]

Saving power can improve gaming performance where the GPU is throttling, but usually gains are small on dGPU, larger on iGPU due to tighter power/thermal constraints.

[agd5f]

Saving power can improve gaming performance where the GPU is throttling, but usually gains are small on dGPU, larger on iGPU due to tighter power/thermal constraints.

In this case, it would only save power in cases where GFX is not in use.

[Adarion]

It looks nice, like some BACO thing. Power-gate what you can power-gate and have a little controller do things separately. Sadly it seems to be RDNA3 only. My Polaris dGPUs are still fine, besides, I currently lack the money for RDNA3. Until I am ready for it, there'll probably be another new generation...

[agd5f]

It looks nice, like some BACO thing. Power-gate what you can power-gate and have a little controller do things separately. Sadly it seems to be RDNA3 only. My Polaris dGPUs are still fine, besides, I currently lack the money for RDNA3. Until I am ready for it, there'll probably be another new generation...

Not exactly. Since RDNA1, GFX and SDMA are on the same power domain so if either is in use the whole domain is powered up. On earlier chips (like vega and polaris), SDMA and GFX were on different power domains. The reason SDMA and GFX were put on the same power domain was to be able to have cache coherency which has its advantages in certain cases. LSDMA is on a separate power domain than GFX and SDMA, but it has lower bandwidth. Trade offs.

[Adarion]

Thanks for the clarification!