This series fixes two distinct classes of pipe FIFO underruns observed during modesets and back-to-back atomic commits.
1. Patch 1 avoids cdclk VCO-change glitches in bxt_modeset_calc_cdclk() by preferring a same-VCO table entry (pure squash, no DBUF ratio change) over an intermediate that drops below min_cdclk or flips the DBUF ratio mid-commit. 2. Patch 2 closes a brief DDB-overlap window when back-to-back commits reshuffle per-plane PLANE_BUF_CFG sub-ranges without changing the per-pipe DBUF allocation, MBUS join or slice mask. Shrinking ranges are pre- programmed and a vblank is awaited so hw retires the old (larger) ranges before grown/new planes occupy the freed space. Nemesa Garg (2): drm/i915/cdclk: Avoid VCO-change glitches drm/i915/wm: wait a vblank before shrinking plane DDB drivers/gpu/drm/i915/display/intel_cdclk.c | 47 +++++++++++++++++++ drivers/gpu/drm/i915/display/skl_watermark.c | 49 ++++++++++++++++++++ 2 files changed, 96 insertions(+) -- 2.25.1
