AMD Continues Working To Mainline Their PTDMA Driver For Linux

Published all the way back in September 2019 was a Linux driver for supporting the Pass-Through DMA controller for EPYC processors. The PTDMA hardware allows for high bandwidth memory-to-memory and I/O copy operations. Now mid-way through 2021 that AMD PTDMA Linux driver remains in the works and is up to its tenth driver revision while waiting to see if it's now ready for mainline or further changes are still deemed necessary.

This AMD PTDMA controller and driver is optimized for use with AMD Non-Transparent Bridge (NTB) devices and not general purpose DMA. NTB is used for in connecting multiple separate memory systems to the same PCI Express fabric. The PTDMA driver supports the 0x1498 (PCI device ID) controller found within EPYC processors since 7002 "Rome".

Following the initial patch series in September 2019, the AMD PTDMA Linux driver quickly went through several rounds of review over the following months. Later revisions continued but took more time between patch submissions while now as of today is up to its tenth revision. This latest revision has various low-level code improvements and clean-ups. The v10 PTDMA patches can be found on the kernel mailing list.

We'll see in the days/weeks ahead if any other issues with the new driver submission are raised or if it's now deemed in good enough shape for finally mainlining in the Linux kernel. Hopefully with AMD continuing to hire more Linux engineers, issues like these with belated drivers will become a thing of the past.