Commit 367d73d2 authored May 31, 2017 by Maarten Lankhorst

drm/i915: Always recompute watermarks when distrust_bios_wm is set, v2.



On some systems there can be a race condition in which no crtc state is
added to the first atomic commit. This results in all crtc's having a
null DDB allocation, causing a FIFO underrun on any update until the
first modeset.

Changes since v1:
- Do not take the connection_mutex, this is already done below.

Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Inspired-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: 98d39494 ("drm/i915/gen9: Compute DDB allocation at atomic
check time (v4)")
Cc: <stable@vger.kernel.org> # v4.8+
Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170531154236.27180-1-maarten.lankhorst@linux.intel.com


Reviewed-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

parent adfdf85d

drivers/gpu/drm/i915/intel_pm.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -4819,10 +4819,18 @@ skl_compute_wm(struct drm_atomic_state *state)
		struct drm_crtc_state *cstate;
		struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
		struct skl_wm_values *results = &intel_state->wm_results;
		struct drm_device *dev = state->dev;
		struct skl_pipe_wm *pipe_wm;
		bool changed = false;
		int ret, i;

		/*
		* When we distrust bios wm we always need to recompute to set the
		* expected DDB allocations for each CRTC.
		*/
		if (to_i915(dev)->wm.distrust_bios_wm)
		changed = true;

		/*
		* If this transaction isn't actually touching any CRTC's, don't
		* bother with watermark calculation. Note that if we pass this
		@@ -4833,6 +4841,7 @@ skl_compute_wm(struct drm_atomic_state *state)
		*/
		for_each_new_crtc_in_state(state, crtc, cstate, i)
		changed = true;

		if (!changed)
		return 0;