[PATCH v4 08/17] drm/i915: Add distrust_bios_wm flag to dev_priv

[Matt Roper <matthew.d.roper@intel.com>]

SKL-style platforms can't fully trust the watermark/DDB settings
programmed by the BIOS and need to do extra sanitization on their first
atomic update.  Add a flag to dev_priv that is set during hardware
readout and cleared at the end of the first commit.

Note that for the somewhat common case where everything is turned off
when the driver starts up, we don't need to bother with a recompute...we
know exactly what the DDB should be (all zero's) so just setup the DDB
directly in that case.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h      |  7 +++++++
 drivers/gpu/drm/i915/intel_display.c |  7 +++++++
 drivers/gpu/drm/i915/intel_pm.c      | 15 ++++++++++++++-
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a67462a..27aaaca 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1993,6 +1993,13 @@ struct drm_i915_private {
 		 * cstate->wm.need_postvbl_update.
 		 */
 		struct mutex wm_mutex;
+
+		/*
+		 * Set during HW readout of watermarks/DDB.  Some platforms
+		 * need to know when we're still using BIOS-provided values
+		 * (which we don't fully trust).
+		 */
+		bool distrust_bios_wm;
 	} wm;
 
 	struct i915_runtime_pm pm;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7acdfa3..3028bf4 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13703,6 +13703,13 @@ static int intel_atomic_commit(struct drm_device *dev,
 			dev_priv->display.optimize_watermarks(intel_cstate);
 	}
 
+	/*
+	 * We've now finished at least one atomic commit following hw readout,
+	 * so any platforms that needed to do extra sanitization of watermarks
+	 * should have done it by now.
+	 */
+	dev_priv->wm.distrust_bios_wm = false;
+
 	for_each_crtc_in_state(state, crtc, old_crtc_state, i) {
 		intel_post_plane_update(to_intel_crtc_state(old_crtc_state));
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 90ba05c..e3877dc 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4021,11 +4021,24 @@ void skl_wm_get_hw_state(struct drm_device *dev)
 	struct skl_ddb_allocation *ddb = &dev_priv->wm.skl_hw.ddb;
 	struct drm_crtc *crtc;
 	struct intel_crtc *intel_crtc;
+	bool any_on = false;
 
 	skl_ddb_get_hw_state(dev_priv, ddb);
-	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
 		skl_pipe_wm_get_hw_state(crtc);
 
+		if (crtc->state->active)
+			any_on = true;
+	}
+
+	if (any_on) {
+		/* Fully recompute DDB on first atomic commit */
+		dev_priv->wm.distrust_bios_wm = true;
+	} else {
+		/* Easy/common case; just sanitize DDB now if everything off */
+		memset(ddb, 0, sizeof(*ddb));
+	}
+
 	/* Calculate plane data rates */
 	for_each_intel_crtc(dev, intel_crtc) {
 		struct intel_crtc_state *cstate = intel_crtc->config;
-- 
2.1.4

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