Vivante galcore module slow load time and NO_DMA_COHERENT

[francescodolcin]

Hi all,

I am using Vivante GPU on i.MX 6Q on Linux.

As already noticed by others (Imx6QP ：Why galcore spend a lot of time loading resources？ ) galcore module is too slow to load (>700ms).

This is not compatible with our application and we need a solution to have a faster loading.

After some investigation we found that setting NO_DMA_COHERENT config option is improving the situation a lot. We have not seen any evident problem doing this (just guessing ... maybe it is working because there is no IOMMU between GPU and i.MX6 processor?).

Any comments?

Any better solution to suggest?

Thanks,

Francesco

[Bio_TICFSL]

Hi Fancesco,

In case of alloc_pages, Pages are provided in sets of 2^N, that could be a big allocations memory wastage, however I agree that NO_DMA_COHERENT improve the galcore loading time.

Regards

[csoapy]

NO_DMA_COHERENT has no obvious improvement on official BSP imx-4.14.98-2.1.0

Here is my test:

[Bio_TICFSL]

Hi Francesco,

Thanks for the tip, however take in mind that when using NO_DMA_COHERENT kernel manages memory via "alloc_pages"

Regards

[francescodolcin]

Hi Bio_TICFSL,

could you please tell me what are the drawbacks of using NO_DMA_COHERENT config option?

And if no drawbacks are expected for what reason is not enabled by default?

Thanks,

Francesco