drm/i915/display: Do both crawl and squash when changing cdclk

For MTL, changing cdclk from between certain frequencies has
both squash and crawl. Use the current cdclk config and
the new(desired) cdclk config to construct a mid cdclk config.
Set the cdclk twice:
- Current cdclk -> mid cdclk
- mid cdclk -> desired cdclk

Driver should not take some Pcode mailbox communication
in the cdclk path for platforms that are Display version 14 and later.

v2: Add check in intel_modeset_calc_cdclk() to avoid cdclk
change via modeset for platforms that support squash_crawl sequences(Ville)

v3: Add checks for:
- scenario where only slow clock is used and
cdclk is actually 0 (bringing up display).
- PLLs are on before looking up the waveform.
- Squash and crawl capability checks.(Ville)

v4: Rebase
- Move checks to be more consistent (Ville)
- Add comments (Bala)
v5:
- Further small changes. Move checks around.
- Make if-else better looking (Ville)

v6: MTl should not follow PUnit mailbox communication as the rest of
gen11+ platforms.(Anusha)

Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221117230002.792096-2-anusha.srivatsa@intel.com

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

@@ -1727,37 +1727,79 @@ static bool cdclk_pll_is_unknown(unsigned int vco)
 	return vco == ~0;
 }
 
-static void bxt_set_cdclk(struct drm_i915_private *dev_priv,
-			  const struct intel_cdclk_config *cdclk_config,
-			  enum pipe pipe)
+static int cdclk_squash_divider(u16 waveform)
+{
+	return hweight16(waveform ?: 0xffff);
+}
+
+static bool cdclk_compute_crawl_and_squash_midpoint(struct drm_i915_private *i915,
+						    const struct intel_cdclk_config *old_cdclk_config,
+						    const struct intel_cdclk_config *new_cdclk_config,
+						    struct intel_cdclk_config *mid_cdclk_config)
+{
+	u16 old_waveform, new_waveform, mid_waveform;
+	int size = 16;
+	int div = 2;
+
+	/* Return if PLL is in an unknown state, force a complete disable and re-enable. */
+	if (cdclk_pll_is_unknown(old_cdclk_config->vco))
+		return false;
+
+	/* Return if both Squash and Crawl are not present */
+	if (!HAS_CDCLK_CRAWL(i915) || !HAS_CDCLK_SQUASH(i915))
+		return false;
+
+	old_waveform = cdclk_squash_waveform(i915, old_cdclk_config->cdclk);
+	new_waveform = cdclk_squash_waveform(i915, new_cdclk_config->cdclk);
+
+	/* Return if Squash only or Crawl only is the desired action */
+	if (old_cdclk_config->vco == 0 || new_cdclk_config->vco == 0 ||
+	    old_cdclk_config->vco == new_cdclk_config->vco ||
+	    old_waveform == new_waveform)
+		return false;
+
+	*mid_cdclk_config = *new_cdclk_config;
+
+	/*
+	 * Populate the mid_cdclk_config accordingly.
+	 * - If moving to a higher cdclk, the desired action is squashing.
+	 * The mid cdclk config should have the new (squash) waveform.
+	 * - If moving to a lower cdclk, the desired action is crawling.
+	 * The mid cdclk config should have the new vco.
+	 */
+
+	if (cdclk_squash_divider(new_waveform) > cdclk_squash_divider(old_waveform)) {
+		mid_cdclk_config->vco = old_cdclk_config->vco;
+		mid_waveform = new_waveform;
+	} else {
+		mid_cdclk_config->vco = new_cdclk_config->vco;
+		mid_waveform = old_waveform;
+	}
+
+	mid_cdclk_config->cdclk = DIV_ROUND_CLOSEST(cdclk_squash_divider(mid_waveform) *
+						    mid_cdclk_config->vco, size * div);
+
+	/* make sure the mid clock came out sane */
+
+	drm_WARN_ON(&i915->drm, mid_cdclk_config->cdclk <
+		    min(old_cdclk_config->cdclk, new_cdclk_config->cdclk));
+	drm_WARN_ON(&i915->drm, mid_cdclk_config->cdclk >
+		    i915->display.cdclk.max_cdclk_freq);
+	drm_WARN_ON(&i915->drm, cdclk_squash_waveform(i915, mid_cdclk_config->cdclk) !=
+		    mid_waveform);
+
+	return true;
+}
+
+static void _bxt_set_cdclk(struct drm_i915_private *dev_priv,
+			   const struct intel_cdclk_config *cdclk_config,
+			   enum pipe pipe)
 {
 	int cdclk = cdclk_config->cdclk;
 	int vco = cdclk_config->vco;
 	u32 val;
 	u16 waveform;
 	int clock;
-	int ret;
-
-	/* Inform power controller of upcoming frequency change. */
-	if (DISPLAY_VER(dev_priv) >= 11)
-		ret = skl_pcode_request(&dev_priv->uncore, SKL_PCODE_CDCLK_CONTROL,
-					SKL_CDCLK_PREPARE_FOR_CHANGE,
-					SKL_CDCLK_READY_FOR_CHANGE,
-					SKL_CDCLK_READY_FOR_CHANGE, 3);
-	else
-		/*
-		 * BSpec requires us to wait up to 150usec, but that leads to
-		 * timeouts; the 2ms used here is based on experiment.
-		 */
-		ret = snb_pcode_write_timeout(&dev_priv->uncore,
-					      HSW_PCODE_DE_WRITE_FREQ_REQ,
-					      0x80000000, 150, 2);
-	if (ret) {
-		drm_err(&dev_priv->drm,
-			"Failed to inform PCU about cdclk change (err %d, freq %d)\n",
-			ret, cdclk);
-		return;
-	}
 
 	if (HAS_CDCLK_CRAWL(dev_priv) && dev_priv->display.cdclk.hw.vco > 0 && vco > 0 &&
 	    !cdclk_pll_is_unknown(dev_priv->display.cdclk.hw.vco)) {
@@ -1793,11 +1835,62 @@ static void bxt_set_cdclk(struct drm_i915_private *dev_priv,
 
 	if (pipe != INVALID_PIPE)
 		intel_crtc_wait_for_next_vblank(intel_crtc_for_pipe(dev_priv, pipe));
+}
+
+static void bxt_set_cdclk(struct drm_i915_private *dev_priv,
+			  const struct intel_cdclk_config *cdclk_config,
+			  enum pipe pipe)
+{
+	struct intel_cdclk_config mid_cdclk_config;
+	int cdclk = cdclk_config->cdclk;
+	int ret = 0;
+
+	/*
+	 * Inform power controller of upcoming frequency change.
+	 * Display versions 14 and beyond do not follow the PUnit
+	 * mailbox communication, skip
+	 * this step.
+	 */
+	if (DISPLAY_VER(dev_priv) >= 14)
+		/* NOOP */;
+	else if (DISPLAY_VER(dev_priv) >= 11)
+		ret = skl_pcode_request(&dev_priv->uncore, SKL_PCODE_CDCLK_CONTROL,
+					SKL_CDCLK_PREPARE_FOR_CHANGE,
+					SKL_CDCLK_READY_FOR_CHANGE,
+					SKL_CDCLK_READY_FOR_CHANGE, 3);
+	else
+		/*
+		 * BSpec requires us to wait up to 150usec, but that leads to
+		 * timeouts; the 2ms used here is based on experiment.
+		 */
+		ret = snb_pcode_write_timeout(&dev_priv->uncore,
+					      HSW_PCODE_DE_WRITE_FREQ_REQ,
+					      0x80000000, 150, 2);
+
+	if (ret) {
+		drm_err(&dev_priv->drm,
+			"Failed to inform PCU about cdclk change (err %d, freq %d)\n",
+			ret, cdclk);
+		return;
+	}
 
-	if (DISPLAY_VER(dev_priv) >= 11) {
+	if (cdclk_compute_crawl_and_squash_midpoint(dev_priv, &dev_priv->display.cdclk.hw,
+						    cdclk_config, &mid_cdclk_config)) {
+		_bxt_set_cdclk(dev_priv, &mid_cdclk_config, pipe);
+		_bxt_set_cdclk(dev_priv, cdclk_config, pipe);
+	} else {
+		_bxt_set_cdclk(dev_priv, cdclk_config, pipe);
+	}
+
+	if (DISPLAY_VER(dev_priv) >= 14)
+		/*
+		 * NOOP - No Pcode communication needed for
+		 * Display versions 14 and beyond
+		 */;
+	else if (DISPLAY_VER(dev_priv) >= 11)
 		ret = snb_pcode_write(&dev_priv->uncore, SKL_PCODE_CDCLK_CONTROL,
 				      cdclk_config->voltage_level);
-	} else {
+	else
 		/*
 		 * The timeout isn't specified, the 2ms used here is based on
 		 * experiment.
@@ -1808,7 +1901,6 @@ static void bxt_set_cdclk(struct drm_i915_private *dev_priv,
 					      HSW_PCODE_DE_WRITE_FREQ_REQ,
 					      cdclk_config->voltage_level,
 					      150, 2);
-	}
 
 	if (ret) {
 		drm_err(&dev_priv->drm,
@@ -1965,6 +2057,28 @@ void intel_cdclk_uninit_hw(struct drm_i915_private *i915)
 		skl_cdclk_uninit_hw(i915);
 }
 
+static bool intel_cdclk_can_crawl_and_squash(struct drm_i915_private *i915,
+					     const struct intel_cdclk_config *a,
+					     const struct intel_cdclk_config *b)
+{
+	u16 old_waveform;
+	u16 new_waveform;
+
+	drm_WARN_ON(&i915->drm, cdclk_pll_is_unknown(a->vco));
+
+	if (a->vco == 0 || b->vco == 0)
+		return false;
+
+	if (!HAS_CDCLK_CRAWL(i915) || !HAS_CDCLK_SQUASH(i915))
+		return false;
+
+	old_waveform = cdclk_squash_waveform(i915, a->cdclk);
+	new_waveform = cdclk_squash_waveform(i915, b->cdclk);
+
+	return a->vco != b->vco &&
+	       old_waveform != new_waveform;
+}
+
 static bool intel_cdclk_can_crawl(struct drm_i915_private *dev_priv,
 				  const struct intel_cdclk_config *a,
 				  const struct intel_cdclk_config *b)
@@ -2771,9 +2885,14 @@ int intel_modeset_calc_cdclk(struct intel_atomic_state *state)
 			pipe = INVALID_PIPE;
 	}
 
-	if (intel_cdclk_can_squash(dev_priv,
-				   &old_cdclk_state->actual,
-				   &new_cdclk_state->actual)) {
+	if (intel_cdclk_can_crawl_and_squash(dev_priv,
+					     &old_cdclk_state->actual,
+					     &new_cdclk_state->actual)) {
+		drm_dbg_kms(&dev_priv->drm,
+			    "Can change cdclk via crawling and squashing\n");
+	} else if (intel_cdclk_can_squash(dev_priv,
+					&old_cdclk_state->actual,
+					&new_cdclk_state->actual)) {
 		drm_dbg_kms(&dev_priv->drm,
 			    "Can change cdclk via squashing\n");
 	} else if (intel_cdclk_can_crawl(dev_priv,