[Intel-gfx] [PATCH 5/5] drm/i915/tgl: Add workaround for incorrect BIOS combo PHY DPLL programming

[Imre Deak]

The TGL A stepping and some B stepping (display C stepping) BIOSes
program the combo PHY DPLL fractional divider value incorrectly, not
applying the Display #22010492432 workaround.

Add a workaround for such BIOS versions, so that the driver selects the
correct WRPLL parameter entry correctly (selecting the same entry from
the table whether or not the fractional divider was adjusted or not by
BIOS according to #22010492432).

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 10 +++++++++-
 1 file changed, 9 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 e7b058340a1a..7968ceb23ab6 100644
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
@@ -3026,7 +3026,15 @@ static bool icl_dp_combo_pll_clock_match(struct drm_i915_private *i915, int cloc
 	if (clock == pll_freq)
 		return true;
 
-	return false;
+	if (!tgl_combo_pll_div_frac_wa_needed(i915) ||
+	    !IS_TGL_DISP_REVID(i915, TGL_REVID_A0, TGL_REVID_C0))
+		return false;
+
+	pll_freq = skl_wrpll_calc_freq(ref_clock,
+				       p->wrpll.dco_integer, p->wrpll.dco_fraction * 2,
+				       pdiv, qdiv, kdiv);
+
+	return clock == pll_freq;
 }
 
 static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
-- 
2.25.1