[Intel-gfx] [PATCH 3/4] drm/i915: Sanitize watermarks after hardware state readout

[Matt Roper]

Although we can do a good job of reading out hardware state, the
graphics firmware may have programmed the watermarks in a creative way
that doesn't match how i915 would have chosen to program them.  We
shouldn't trust the firmware's watermark programming, but should rather
re-calculate how we think WM's should be programmed and then shove those
values into the hardware.

We can do this pretty easily by creating a dummy top-level state,
running it through the check process to calculate all the values, and
then just programming the watermarks for each CRTC.

Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h      |  1 +
 drivers/gpu/drm/i915/intel_display.c | 51 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_pm.c      | 14 +++++-----
 3 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 20cd6d8..09807c8 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -629,6 +629,7 @@ struct drm_i915_display_funcs {
 			  struct dpll *best_clock);
 	int (*compute_pipe_wm)(struct intel_crtc *crtc,
 			       struct drm_atomic_state *state);
+	void (*program_watermarks)(struct intel_crtc_state *cstate);
 	void (*update_wm)(struct drm_crtc *crtc);
 	int (*modeset_calc_cdclk)(struct drm_atomic_state *state);
 	void (*modeset_commit_cdclk)(struct drm_atomic_state *state);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7b3cfb6..47a67e0 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15436,6 +15436,54 @@ static void intel_modeset_readout_hw_state(struct drm_device *dev)
 	}
 }
 
+/*
+ * Calculate what we think the watermarks should be for the state we've read
+ * out of the hardware and then immediately program those watermarks so that
+ * we ensure the hardware settings match our internal state.
+ */
+static void sanitize_watermarks(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_atomic_state *state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *cstate;
+	int ret;
+	int i;
+
+	/* Only supported on platforms that use atomic watermark design */
+	if (!dev_priv->display.program_watermarks)
+		return;
+
+	/*
+	 * Calculate what we think WM's should be by creating a dummy state and
+	 * running it through the atomic check code.
+	 */
+	state = drm_atomic_helper_duplicate_state(dev,
+						  dev->mode_config.acquire_ctx);
+	if (WARN_ON(IS_ERR(state)))
+		return;
+
+	ret = intel_atomic_check(dev, state);
+	if (ret) {
+		/*
+		 * Just give up and leave watermarks untouched if we get an
+		 * error back from 'check'
+		 */
+		DRM_DEBUG_KMS("Could not determine valid watermarks for inherited state\n");
+		return;
+	}
+
+	/* Write calculated watermark values back */
+	to_i915(dev)->wm.config = to_intel_atomic_state(state)->wm_config;
+	for_each_crtc_in_state(state, crtc, cstate, i) {
+		struct intel_crtc_state *cs = to_intel_crtc_state(cstate);
+
+		dev_priv->display.program_watermarks(cs);
+	}
+
+	drm_atomic_state_free(state);
+}
+
 /* Scan out the current hw modeset state,
  * and sanitizes it to the current state
  */
@@ -15491,6 +15539,9 @@ intel_modeset_setup_hw_state(struct drm_device *dev)
 			modeset_put_power_domains(dev_priv, put_domains);
 	}
 	intel_display_set_init_power(dev_priv, false);
+
+	/* Make sure hardware watermarks really match the state we read out */
+	sanitize_watermarks(dev);
 }
 
 void intel_display_resume(struct drm_device *dev)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 180348b..fbcb072 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3611,15 +3611,19 @@ static void skl_update_wm(struct drm_crtc *crtc)
 	dev_priv->wm.skl_hw = *results;
 }
 
-static void ilk_program_watermarks(struct drm_i915_private *dev_priv)
+static void ilk_program_watermarks(struct intel_crtc_state *cstate)
 {
-	struct drm_device *dev = dev_priv->dev;
+	struct drm_crtc *crtc = cstate->base.crtc;
+	struct drm_device *dev = crtc->dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_pipe_wm lp_wm_1_2 = {}, lp_wm_5_6 = {}, *best_lp_wm;
 	struct ilk_wm_maximums max;
 	struct intel_wm_config *config = &dev_priv->wm.config;
 	struct ilk_wm_values results = {};
 	enum intel_ddb_partitioning partitioning;
 
+	to_intel_crtc(crtc)->wm.active.ilk = cstate->wm.optimal.ilk;
+
 	ilk_compute_wm_maximums(dev, 1, config, INTEL_DDB_PART_1_2, &max);
 	ilk_wm_merge(dev, config, &max, &lp_wm_1_2);
 
@@ -3644,7 +3648,6 @@ static void ilk_program_watermarks(struct drm_i915_private *dev_priv)
 
 static void ilk_update_wm(struct drm_crtc *crtc)
 {
-	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	struct intel_crtc_state *cstate = to_intel_crtc_state(crtc->state);
 
@@ -3662,9 +3665,7 @@ static void ilk_update_wm(struct drm_crtc *crtc)
 		intel_wait_for_vblank(crtc->dev, intel_crtc->pipe);
 	}
 
-	intel_crtc->wm.active.ilk = cstate->wm.optimal.ilk;
-
-	ilk_program_watermarks(dev_priv);
+	ilk_program_watermarks(cstate);
 }
 
 static void skl_pipe_wm_active_state(uint32_t val,
@@ -6972,6 +6973,7 @@ void intel_init_pm(struct drm_device *dev)
 		     dev_priv->wm.spr_latency[0] && dev_priv->wm.cur_latency[0])) {
 			dev_priv->display.update_wm = ilk_update_wm;
 			dev_priv->display.compute_pipe_wm = ilk_compute_pipe_wm;
+			dev_priv->display.program_watermarks = ilk_program_watermarks;
 		} else {
 			DRM_DEBUG_KMS("Failed to read display plane latency. "
 				      "Disable CxSR\n");
-- 
2.1.4