AMD PTDMA Driver Revised Ahead Of Its Possible Inclusion For Linux 5.15
One of the AMD patch series that has been in the works for more than one year is the PTDMA driver providing pass-through DMA engine support on Linux. The driver is now up to its eleventh revision but the mainlining might happen soon.
The AMD PTDMA Linux driver effort dates back to September 2019 for enabling their PTDMA controller in performing high bandwidth memory-to-memory and I/O copy operations. Modern AMD CPUs support multiple PTDMA controllers, the PTDMA driver hooks into the kernel's direct memory access (DMA) subsystem and is intended to be used with AMD Non-Transparent Bridge (NTB) devices but not for general purpose peripheral DMA.
The prior AMD PTDMA v10 patches were sent back around the time of the Linux 5.14 merge window while the DMA subsystem maintainer Vinod Koul had commented the patches were still in his review queue when prompted by the AMD engineer involved over the status of getting the patches picked up.
This week the v11 patches were sent out with various code improvements. Given there is still a few weeks until the Linux 5.15 merge window, we'll see now if the work is in a state ready for mainlining.