AMD PTDMA Driver Landing For Linux 5.15 After Two Years In The Works
Going back to September 2019 was work on the AMD PTDMA driver for supporting this controller found on modern AMD processors for high bandwidth memory-to-memory and I/O copy operations. With the Linux 5.15 cycle the AMD PTDMA driver is finally being merged to the mainline kernel.
AMD EPYC processors feature multiple PTDMA device instances. While the PTDMA controllers have been found in AMD processors already, the upstreaming process has taken two years and gone through more than ten rounds of code review to address outstanding items and other suggestions for improvements.
The AMD PassThru DMA driver was last revised in August and after v11 was published was deemed ready to go. This driver interfaces with the Linux kernel's DMA subsystem.
The AMD PTDMA for high bandwidth memory-to-memory and I/O copies aren't good for general purpose peripheral DMA but cater to AMD Non-Transparent Bridge (NTB) device usage.
This driver, simply called "ptdma", comes in at a little more than one thousand lines of code. It was sent in yesterday as part of the dmaengine updates for Linux 5.15.