[Intel-gfx] [PATCH 3/5] drm/i915/icl: Cross check the combo PLL WRPLL parameters wrt. hard-coded PLL freqs

[Imre Deak]

When selecting the WRPLL dividers for a given port clock/PLL freq, the
hard-coded PLL freq in a table entry can be calculated using the rest of
parameters in the same entry. Cross-check if the hard coded values match
what we calculate with the formula.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 26 ++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
index e3370c8dccc8..ded2b2dfe319 100644
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
@@ -3002,6 +3002,30 @@ static const struct skl_wrpll_params tgl_tbt_pll_38_4MHz_values = {
 	.pdiv = 0, .kdiv = 0, .qdiv_mode = 0, .qdiv_ratio = 0,
 };
 
+static int icl_wrpll_ref_clock(struct drm_i915_private *i915);
+
+static bool icl_dp_combo_pll_clock_match(struct drm_i915_private *i915, int clock,
+					 const struct icl_combo_pll_params *p)
+{
+	int ref_clock = icl_wrpll_ref_clock(i915);
+	int pll_freq;
+	u32 pdiv;
+	u32 qdiv;
+	u32 kdiv;
+
+	cnl_wrpll_decode_divs(&p->wrpll, &pdiv, &qdiv, &kdiv);
+
+	pll_freq = skl_wrpll_calc_freq(ref_clock,
+				       p->wrpll.dco_integer, p->wrpll.dco_fraction,
+				       pdiv, qdiv, kdiv);
+	drm_WARN_ON(&i915->drm, pll_freq != p->clock);
+
+	if (clock == pll_freq)
+		return true;
+
+	return false;
+}
+
 static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
 				  struct skl_wrpll_params *pll_params)
 {
@@ -3014,7 +3038,7 @@ static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(icl_dp_combo_pll_24MHz_values); i++) {
-		if (clock == params[i].clock) {
+		if (icl_dp_combo_pll_clock_match(dev_priv, clock, &params[i])) {
 			*pll_params = params[i].wrpll;
 			return true;
 		}
-- 
2.25.1