Improved Tear-Free Rendering For Radeon DDX With PRIME

For those making use of the xf86-video-ati DDX driver in a PRIME-capable system with Radeon GPU, there's more effective tear-free rendering support with the latest development code.

In addition to Michel Dänzer fixing a Mesa DRI3 performance issue, separately, he also landed commits today to improve the Radeon X.Org driver's TearFree rendering for PRIME systems.

He first had a big patch to synchronize scanout pixmaps for TearFree, the DDX option aimed to deliver tear-free rendering. With that he explained, "Copy the damaged areas which are still valid in the other scanout pixmap from there, then only copy the remaining damaged area from the screen pixmap. This is slightly more efficient (only needs one Damage record instead of two, and only needs to copy each screen update across PCIe once with ShadowPrimary and a discrete GPU), and will be significantly more efficient for PRIME with the following change."

That was followed by the change to make TearFree effective with PRIME slave scanouts to prevent tearing. But there can still be tearing with the Radeon DDX driver when enabling TearFree on PRIME setups if the primary GPU is using a different DDX driver.