drm/i915/gen9: Compute DDB allocation at atomic check time (v4)
Calculate the DDB blocks needed to satisfy the current atomic transaction at atomic check time. This is a prerequisite to calculating SKL watermarks during the 'check' phase and rejecting any configurations that we can't find valid watermarks for. Due to the nature of DDB allocation, it's possible for the addition of a new CRTC to make the watermark configuration already in use on another, unchanged CRTC become invalid. A change in which CRTC's are active triggers a recompute of the entire DDB, which unfortunately means we need to disallow any other atomic commits from racing with such an update. If the active CRTC's change, we need to grab the lock on all CRTC's and run all CRTC's through their 'check' handler to recompute and re-check their per-CRTC DDB allocations. Note that with this patch we only compute the DDB allocation but we don't actually use the computed values during watermark programming yet. For ease of review/testing/bisecting, we still recompute the DDB at watermark programming time and just WARN() if it doesn't match the precomputed values. A future patch will switch over to using the precomputed values once we're sure they're being properly computed. Another clarifying note: DDB allocation itself shouldn't ever fail with the algorithm we use today (i.e., we have enough DDB blocks on BXT to support the minimum needs of the worst-case scenario of every pipe/plane enabled at full size). However the watermarks calculations based on the DDB may fail and we'll be moving those to the atomic check as well in future patches. v2: - Skip DDB calculations in the rare case where our transaction doesn't actually touch any CRTC's at all. Assuming at least one CRTC state is present in our transaction, then it means we can't race with any transactions that would update dev_priv->active_crtcs (which requires _all_ CRTC locks). v3: - Also calculate DDB during initial hw readout, to prevent using incorrect bios values. (Maarten) v4: - Use new distrust_bios_wm flag instead of skip_initial_wm (which was never actually set). - Set intel_state->active_pipe_changes instead of just realloc_pipes Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Lyude Paul <cpaul@redhat.com> Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com> Signed-off-by: NMatt Roper <matthew.d.roper@intel.com> Signed-off-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com> Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1463061971-19638-10-git-send-email-matthew.d.roper@intel.com
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