drm/i915: Adjust CDCLK accordingly to our DBuf bw needs

According to BSpec max BW per slice is calculated using formula
Max BW = CDCLK * 64. Currently when calculating min CDCLK we
account only per plane requirements, however in order to avoid
FIFO underruns we need to estimate accumulated BW consumed by
all planes(ddb entries basically) residing on that particular
DBuf slice. This will allow us to put CDCLK lower and save power
when we don't need that much bandwidth or gain additional
performance once plane consumption grows.

v2: - Fix long line warning
    - Limited new DBuf bw checks to only gens >= 11

v3: - Lets track used Dbuf bw per slice and per crtc in bw state
      (or may be in DBuf state in future), that way we don't need
      to have all crtcs in state and those only if we detect if
      are actually going to change cdclk, just same way as we
      do with other stuff, i.e intel_atomic_serialize_global_state
      and co. Just as per Ville's paradigm.
    - Made dbuf bw calculation procedure look nicer by introducing
      for_each_dbuf_slice_in_mask - we often will now need to iterate
      slices using mask.
    - According to experimental results CDCLK * 64 accounts for
      overall bandwidth across all dbufs, not per dbuf.

v4: - Fixed missing const(Ville)
    - Removed spurious whitespaces(Ville)
    - Fixed local variable init(reduced scope where not needed)
    - Added some comments about data rate for planar formats
    - Changed struct intel_crtc_bw to intel_dbuf_bw
    - Moved dbuf bw calculation to intel_compute_min_cdclk(Ville)

v5: - Removed unneeded macro

v6: - Prevent too frequent CDCLK switching back and forth:
      Always switch to higher CDCLK when needed to prevent bandwidth
      issues, however don't switch to lower CDCLK earlier than once
      in 30 minutes in order to prevent constant modeset blinking.
      We could of course not switch back at all, however this is
      bad from power consumption point of view.

v7: - Fixed to track cdclk using bw_state, modeset will be now
      triggered only when CDCLK change is really needed.

v8: - Lock global state if bw_state->min_cdclk is changed.
    - Try getting bw_state only if there are crtcs in the commit
      (need to have read-locked global state)

v9: - Do not do Dbuf bw check for gens < 9 - triggers WARN
      as ddb_size is 0.

v10: - Lock global state for older gens as well.

v11: - Define new bw_calc_min_cdclk hook, instead of using
       a condition(Manasi Navare)

v12: - Fixed rebase conflict

v13: - Added spaces after declarations to make checkpatch happy.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200520150058.16123-1-stanislav.lisovskiy@intel.com

drivers/gpu/drm/i915/display/intel_bw.c

@@ -6,11 +6,12 @@
 #include <drm/drm_atomic_state_helper.h>
 
 #include "intel_bw.h"
+#include "intel_pm.h"
 #include "intel_display_types.h"
 #include "intel_sideband.h"
 #include "intel_atomic.h"
 #include "intel_pm.h"
-
+#include "intel_cdclk.h"
 
 /* Parameters for Qclk Geyserville (QGV) */
 struct intel_qgv_point {
@@ -351,7 +352,6 @@ static unsigned int intel_bw_crtc_data_rate(const struct intel_crtc_state *crtc_
 
 	return data_rate;
 }
-
 void intel_bw_crtc_update(struct intel_bw_state *bw_state,
 			  const struct intel_crtc_state *crtc_state)
 {
@@ -428,6 +428,123 @@ intel_atomic_get_bw_state(struct intel_atomic_state *state)
 	return to_intel_bw_state(bw_state);
 }
 
+int skl_bw_calc_min_cdclk(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+	int i;
+	const struct intel_crtc_state *crtc_state;
+	struct intel_crtc *crtc;
+	int max_bw = 0;
+	int slice_id;
+	struct intel_bw_state *new_bw_state = NULL;
+	struct intel_bw_state *old_bw_state = NULL;
+
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		enum plane_id plane_id;
+		struct intel_dbuf_bw *crtc_bw;
+
+		new_bw_state = intel_atomic_get_bw_state(state);
+		if (IS_ERR(new_bw_state))
+			return PTR_ERR(new_bw_state);
+
+		crtc_bw = &new_bw_state->dbuf_bw[crtc->pipe];
+
+		memset(&crtc_bw->used_bw, 0, sizeof(crtc_bw->used_bw));
+
+		for_each_plane_id_on_crtc(crtc, plane_id) {
+			const struct skl_ddb_entry *plane_alloc =
+				&crtc_state->wm.skl.plane_ddb_y[plane_id];
+			const struct skl_ddb_entry *uv_plane_alloc =
+				&crtc_state->wm.skl.plane_ddb_uv[plane_id];
+			unsigned int data_rate = crtc_state->data_rate[plane_id];
+			unsigned int dbuf_mask = 0;
+
+			dbuf_mask |= skl_ddb_dbuf_slice_mask(dev_priv, plane_alloc);
+			dbuf_mask |= skl_ddb_dbuf_slice_mask(dev_priv, uv_plane_alloc);
+
+			/*
+			 * FIXME: To calculate that more properly we probably need to
+			 * to split per plane data_rate into data_rate_y and data_rate_uv
+			 * for multiplanar formats in order not to get accounted those twice
+			 * if they happen to reside on different slices.
+			 * However for pre-icl this would work anyway because we have only single
+			 * slice and for icl+ uv plane has non-zero data rate.
+			 * So in worst case those calculation are a bit pessimistic, which
+			 * shouldn't pose any significant problem anyway.
+			 */
+			for_each_dbuf_slice_in_mask(slice_id, dbuf_mask)
+				crtc_bw->used_bw[slice_id] += data_rate;
+		}
+
+		for_each_dbuf_slice(slice_id) {
+			/*
+			 * Current experimental observations show that contrary to BSpec
+			 * we get underruns once we exceed 64 * CDCLK for slices in total.
+			 * As a temporary measure in order not to keep CDCLK bumped up all the
+			 * time we calculate CDCLK according to this formula for  overall bw
+			 * consumed by slices.
+			 */
+			max_bw += crtc_bw->used_bw[slice_id];
+		}
+
+		new_bw_state->min_cdclk = max_bw / 64;
+
+		old_bw_state = intel_atomic_get_old_bw_state(state);
+	}
+
+	if (!old_bw_state)
+		return 0;
+
+	if (new_bw_state->min_cdclk != old_bw_state->min_cdclk) {
+		int ret = intel_atomic_lock_global_state(&new_bw_state->base);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+int intel_bw_calc_min_cdclk(struct intel_atomic_state *state)
+{
+	int i;
+	const struct intel_crtc_state *crtc_state;
+	struct intel_crtc *crtc;
+	int min_cdclk = 0;
+	struct intel_bw_state *new_bw_state = NULL;
+	struct intel_bw_state *old_bw_state = NULL;
+
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		struct intel_cdclk_state *cdclk_state;
+
+		new_bw_state = intel_atomic_get_bw_state(state);
+		if (IS_ERR(new_bw_state))
+			return PTR_ERR(new_bw_state);
+
+		cdclk_state = intel_atomic_get_cdclk_state(state);
+		if (IS_ERR(cdclk_state))
+			return PTR_ERR(cdclk_state);
+
+		min_cdclk = max(cdclk_state->min_cdclk[crtc->pipe], min_cdclk);
+
+		new_bw_state->min_cdclk = min_cdclk;
+
+		old_bw_state = intel_atomic_get_old_bw_state(state);
+	}
+
+	if (!old_bw_state)
+		return 0;
+
+	if (new_bw_state->min_cdclk != old_bw_state->min_cdclk) {
+		int ret = intel_atomic_lock_global_state(&new_bw_state->base);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int intel_bw_atomic_check(struct intel_atomic_state *state)
 {
 	struct drm_i915_private *dev_priv = to_i915(state->base.dev);

drivers/gpu/drm/i915/display/intel_bw.h

@@ -10,13 +10,19 @@
 
 #include "intel_display.h"
 #include "intel_global_state.h"
+#include "intel_display_power.h"
 
 struct drm_i915_private;
 struct intel_atomic_state;
 struct intel_crtc_state;
 
+struct intel_dbuf_bw {
+	int used_bw[I915_MAX_DBUF_SLICES];
+};
+
 struct intel_bw_state {
 	struct intel_global_state base;
+	struct intel_dbuf_bw dbuf_bw[I915_MAX_PIPES];
 
 	/*
 	 * Contains a bit mask, used to determine, whether correspondent
@@ -36,6 +42,8 @@ struct intel_bw_state {
 
 	/* bitmask of active pipes */
 	u8 active_pipes;
+
+	int min_cdclk;
 };
 
 #define to_intel_bw_state(x) container_of((x), struct intel_bw_state, base)
@@ -56,5 +64,7 @@ void intel_bw_crtc_update(struct intel_bw_state *bw_state,
 			  const struct intel_crtc_state *crtc_state);
 int icl_pcode_restrict_qgv_points(struct drm_i915_private *dev_priv,
 				  u32 points_mask);
+int intel_bw_calc_min_cdclk(struct intel_atomic_state *state);
+int skl_bw_calc_min_cdclk(struct intel_atomic_state *state);
 
 #endif /* __INTEL_BW_H__ */

drivers/gpu/drm/i915/display/intel_cdclk.c

@@ -21,10 +21,12 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include <linux/time.h>
 #include "intel_atomic.h"
 #include "intel_cdclk.h"
 #include "intel_display_types.h"
 #include "intel_sideband.h"
+#include "intel_bw.h"
 
 /**
  * DOC: CDCLK / RAWCLK
@@ -2093,11 +2095,9 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
 static int intel_compute_min_cdclk(struct intel_cdclk_state *cdclk_state)
 {
 	struct intel_atomic_state *state = cdclk_state->base.state;
-	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
 	struct intel_crtc *crtc;
 	struct intel_crtc_state *crtc_state;
 	int min_cdclk, i;
-	enum pipe pipe;
 
 	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
 		int ret;
@@ -2117,8 +2117,18 @@ static int intel_compute_min_cdclk(struct intel_cdclk_state *cdclk_state)
 	}
 
 	min_cdclk = cdclk_state->force_min_cdclk;
-	for_each_pipe(dev_priv, pipe)
-		min_cdclk = max(cdclk_state->min_cdclk[pipe], min_cdclk);
+
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		struct intel_bw_state *bw_state;
+
+		min_cdclk = max(cdclk_state->min_cdclk[crtc->pipe], min_cdclk);
+
+		bw_state = intel_atomic_get_bw_state(state);
+		if (IS_ERR(bw_state))
+			return PTR_ERR(bw_state);
+
+		min_cdclk = max(bw_state->min_cdclk, min_cdclk);
+	}
 
 	return min_cdclk;
 }
@@ -2790,25 +2800,30 @@ void intel_init_cdclk_hooks(struct drm_i915_private *dev_priv)
 {
 	if (INTEL_GEN(dev_priv) >= 12) {
 		dev_priv->display.set_cdclk = bxt_set_cdclk;
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bxt_modeset_calc_cdclk;
 		dev_priv->display.calc_voltage_level = tgl_calc_voltage_level;
 		dev_priv->cdclk.table = icl_cdclk_table;
 	} else if (IS_ELKHARTLAKE(dev_priv)) {
 		dev_priv->display.set_cdclk = bxt_set_cdclk;
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bxt_modeset_calc_cdclk;
 		dev_priv->display.calc_voltage_level = ehl_calc_voltage_level;
 		dev_priv->cdclk.table = icl_cdclk_table;
 	} else if (INTEL_GEN(dev_priv) >= 11) {
 		dev_priv->display.set_cdclk = bxt_set_cdclk;
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bxt_modeset_calc_cdclk;
 		dev_priv->display.calc_voltage_level = icl_calc_voltage_level;
 		dev_priv->cdclk.table = icl_cdclk_table;
 	} else if (IS_CANNONLAKE(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = bxt_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bxt_modeset_calc_cdclk;
 		dev_priv->display.calc_voltage_level = cnl_calc_voltage_level;
 		dev_priv->cdclk.table = cnl_cdclk_table;
 	} else if (IS_GEN9_LP(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = bxt_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bxt_modeset_calc_cdclk;
 		dev_priv->display.calc_voltage_level = bxt_calc_voltage_level;
@@ -2817,18 +2832,23 @@ void intel_init_cdclk_hooks(struct drm_i915_private *dev_priv)
 		else
 			dev_priv->cdclk.table = bxt_cdclk_table;
 	} else if (IS_GEN9_BC(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = skl_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = skl_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = skl_modeset_calc_cdclk;
 	} else if (IS_BROADWELL(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = intel_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = bdw_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = bdw_modeset_calc_cdclk;
 	} else if (IS_CHERRYVIEW(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = intel_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = chv_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = vlv_modeset_calc_cdclk;
 	} else if (IS_VALLEYVIEW(dev_priv)) {
+		dev_priv->display.bw_calc_min_cdclk = intel_bw_calc_min_cdclk;
 		dev_priv->display.set_cdclk = vlv_set_cdclk;
 		dev_priv->display.modeset_calc_cdclk = vlv_modeset_calc_cdclk;
 	} else {
+		dev_priv->display.bw_calc_min_cdclk = intel_bw_calc_min_cdclk;
 		dev_priv->display.modeset_calc_cdclk = fixed_modeset_calc_cdclk;
 	}
 

drivers/gpu/drm/i915/display/intel_cdclk.h

@@ -7,7 +7,6 @@
 #define __INTEL_CDCLK_H__
 
 #include <linux/types.h>
-
 #include "i915_drv.h"
 #include "intel_display.h"
 #include "intel_global_state.h"

drivers/gpu/drm/i915/display/intel_display.c

@@ -14708,16 +14708,14 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
 static int intel_atomic_check_cdclk(struct intel_atomic_state *state,
 				    bool *need_cdclk_calc)
 {
-	struct intel_cdclk_state *new_cdclk_state;
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
 	int i;
 	struct intel_plane_state *plane_state;
 	struct intel_plane *plane;
 	int ret;
-
-	new_cdclk_state = intel_atomic_get_new_cdclk_state(state);
-	if (new_cdclk_state && new_cdclk_state->force_min_cdclk_changed)
-		*need_cdclk_calc = true;
-
+	struct intel_cdclk_state *new_cdclk_state;
+	struct intel_crtc_state *new_crtc_state;
+	struct intel_crtc *crtc;
 	/*
 	 * active_planes bitmask has been updated, and potentially
 	 * affected planes are part of the state. We can now
@@ -14729,6 +14727,35 @@ static int intel_atomic_check_cdclk(struct intel_atomic_state *state,
 			return ret;
 	}
 
+	new_cdclk_state = intel_atomic_get_new_cdclk_state(state);
+
+	if (new_cdclk_state && new_cdclk_state->force_min_cdclk_changed)
+		*need_cdclk_calc = true;
+
+	ret = dev_priv->display.bw_calc_min_cdclk(state);
+	if (ret)
+		return ret;
+
+	if (!new_cdclk_state)
+		return 0;
+
+	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
+		struct intel_bw_state *bw_state;
+		int min_cdclk = 0;
+
+		min_cdclk = max(new_cdclk_state->min_cdclk[crtc->pipe], min_cdclk);
+
+		bw_state = intel_atomic_get_bw_state(state);
+		if (IS_ERR(bw_state))
+			return PTR_ERR(bw_state);
+
+		/*
+		 * Currently do this change only if we need to increase
+		 */
+		if (bw_state->min_cdclk > min_cdclk)
+			*need_cdclk_calc = true;
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/i915/i915_drv.h

@@ -273,6 +273,7 @@ struct drm_i915_display_funcs {
 	void (*set_cdclk)(struct drm_i915_private *dev_priv,
 			  const struct intel_cdclk_config *cdclk_config,
 			  enum pipe pipe);
+	int (*bw_calc_min_cdclk)(struct intel_atomic_state *state);
 	int (*get_fifo_size)(struct drm_i915_private *dev_priv,
 			     enum i9xx_plane_id i9xx_plane);
 	int (*compute_pipe_wm)(struct intel_crtc_state *crtc_state);