[Intel-gfx] [PATCH 2/3] drm/i915/display: Do both crawl and squash when changing cdclk

[Anusha Srivatsa <anusha.srivatsa@intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

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>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 177 +++++++++++++++++----
 1 file changed, 146 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 25d01271dc09..ddbe94aac293 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -1727,37 +1727,77 @@ 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;
+
+	drm_WARN_ON(&i915->drm, cdclk_pll_is_unknown(old_cdclk_config->vco));
+
+	/* 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 +1833,62 @@ 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;
 
-	if (DISPLAY_VER(dev_priv) >= 11) {
+	/*
+	 * 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 (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 +1899,6 @@ 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 +2055,26 @@ 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;
+
+	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 +2881,14 @@ 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,
-- 
2.25.1