I've got a 4k display that supports a refresh rate of 120Hz at 1920x1080 but can't get better than 60Hz from it at that resolution with the Linux Catalyst drivers. From section 1.3 of the AMD LGD Specification, this appears to be a normal, albeit unsatisfying behavior.
Has anyone successfully altered their GPU's pixel clock under Linux, or otherwise know of a way to configure around this limitation? Alternatively, does anyone know which video cards currently support at least a 1920x1080_120 native display mode under Linux? Any brand.