Playing audio over DP MST or just enabling it during boot caused underruns on BDW and SKL. The underruns are followed by displays cycling on-off. Debugging the underruns led to the understanding this was not a MST specific issue but specific to the HBR2 configuration. There are two solutions depending on the platform:
a) BDW - Increase the cdclk to at least 432 MHz in DP HBR2, x4 configs. b) SKL, BXT and KBL - Enable DP stall fix (increasing the cdclk works too). I have tested this only on SKL and it would be great if somebody else can share the results for other platforms. Dhinakaran Pandiyan (2): drm/i915/dp: Enable DP audio stall fix for gen9 platforms drm/i915/dp: BDW cdclk fix for DP audio drivers/gpu/drm/i915/i915_reg.h | 5 +++++ drivers/gpu/drm/i915/intel_ddi.c | 38 ++++++++++++++++++++++++++++++++++++ drivers/gpu/drm/i915/intel_display.c | 28 +++++++++++++++++++++++--- drivers/gpu/drm/i915/intel_drv.h | 2 ++ 4 files changed, 70 insertions(+), 3 deletions(-) -- 2.7.4 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
