One of the underlying features that has been lacking from the ATI R600/700 DRM / kernel mode-setting driver on Linux has been support for interrupts, which is needed for the sync-to-vblank operation and other important areas. Interrupts support has been lacking since AMD has not yet published any documentation concerning them for the Radeon HD 2000, 3000, and 4000 series ASICs, but today their code has cleared the legal review process for publishing. AMD's Alex Deucher has just pushed out the code that enables the use of interrupts for R600/700 graphics processors via a ring buffer. This interrupts support also requires two new firmware files to be loaded by the open-source driver.
The 700 line patch that adds interrupts support for the ATI R600/700 series in the DRM/KMS code-base can currently be found on the dri-devel list
along with the new firmware
for the interrupt controller. This is great timing to hopefully be pushed into the DRM pull request for the Linux 2.6.33 kernel.