Questions about smmu

Hi everyone:
we have a pcie device(tw6869), we found if we disable pcie smmu, the driver could not use GFP_DMA32 in dma_alloc_coherent. But our tw6869 only support 32bit to solve it?


Did you ever solve this problem? I am working on the same issue right now.


This is not possible if SMMU is disabled for PCIe as the full system memory would be available to be used by the hardware.
BTW, what is the reason why SMMU is disabled in the first place? If the driver is written adhering to PCIe device driver writing guidelines, then, there shouldn’t be an issue for it to work in a system with/without SMMU.