Quoting Maarten Lankhorst (2018-03-13 09:28:55)
On fi-cnl-y3 we have 2 modes that differ only by crtc_clock. This means that if we request the normal mode, we automatically get the downclocked mode.
This can be seen during boot: [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:101:eDP-1] probed modes : [drm:drm_mode_debug_printmodeline] Modeline 102:"3840x2160" 60 533250 3840 3888 3920 4000 2160 2163 2168 2222 0x48 0xa [drm:drm_mode_debug_printmodeline] Modeline 103:"3840x2160" 48 426600 3840 3888 3920 4000 2160 2163 2168 2222 0x40 0xa ... [drm:intel_dump_pipe_config [i915]] [CRTC:51:pipe A][modeset] [drm:intel_dump_pipe_config [i915]] output_types: EDP (0x100) [drm:intel_dump_pipe_config [i915]] cpu_transcoder: EDP, pipe bpp: 24, dithering: 0 [drm:intel_dump_pipe_config [i915]] dp m_n: lanes: 4; gmch_m: 4970250, gmch_n: 8388608, link_m: 828375, link_n: 1048576, tu: 64 [drm:intel_dump_pipe_config [i915]] dp m2_n2: lanes: 4; gmch_m: 4970250, gmch_n: 8388608, link_m: 828375, link_n: 1048576, tu: 64 [drm:intel_dump_pipe_config [i915]] audio: 0, infoframes: 0 [drm:intel_dump_pipe_config [i915]] requested mode: [drm:drm_mode_debug_printmodeline] Modeline 0:"3840x2160" 60 533250 3840 3888 3920 4000 2160 2163 2168 2222 0x48 0xa [drm:intel_dump_pipe_config [i915]] adjusted mode: [drm:drm_mode_debug_printmodeline] Modeline 0:"3840x2160" 48 426600 3840 3888 3920 4000 2160 2163 2168 2222 0x40 0xa
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105469 ?