drm/i915/bxt: add DDI port HW readout support

Add support for reading out the HW state for DDI ports. Since the actual
programming is very similar to the CHV/VLV DPIO PLL programming we can
reuse much of the logic from there.

This fixes the state checker failures I saw on my BXT with HDMI output.

v2:
- rebased on v2 of patch 4/5
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -1170,10 +1170,12 @@ enum skl_disp_power_wells {
 #define _PORT_PLL_EBB_0_A		0x162034
 #define _PORT_PLL_EBB_0_B		0x6C034
 #define _PORT_PLL_EBB_0_C		0x6C340
-#define   PORT_PLL_P1_MASK		(0x07 << 13)
-#define   PORT_PLL_P1(x)		((x)  << 13)
-#define   PORT_PLL_P2_MASK		(0x1f << 8)
-#define   PORT_PLL_P2(x)		((x)  << 8)
+#define   PORT_PLL_P1_SHIFT		13
+#define   PORT_PLL_P1_MASK		(0x07 << PORT_PLL_P1_SHIFT)
+#define   PORT_PLL_P1(x)		((x)  << PORT_PLL_P1_SHIFT)
+#define   PORT_PLL_P2_SHIFT		8
+#define   PORT_PLL_P2_MASK		(0x1f << PORT_PLL_P2_SHIFT)
+#define   PORT_PLL_P2(x)		((x)  << PORT_PLL_P2_SHIFT)
 #define BXT_PORT_PLL_EBB_0(port)	_PORT3(port, _PORT_PLL_EBB_0_A, \
 						_PORT_PLL_EBB_0_B,	\
 						_PORT_PLL_EBB_0_C)
@@ -1193,8 +1195,9 @@ enum skl_disp_power_wells {
 /* PORT_PLL_0_A */
 #define   PORT_PLL_M2_MASK		0xFF
 /* PORT_PLL_1_A */
-#define   PORT_PLL_N_MASK		(0x0F << 8)
-#define   PORT_PLL_N(x)			((x) << 8)
+#define   PORT_PLL_N_SHIFT		8
+#define   PORT_PLL_N_MASK		(0x0F << PORT_PLL_N_SHIFT)
+#define   PORT_PLL_N(x)			((x) << PORT_PLL_N_SHIFT)
 /* PORT_PLL_2_A */
 #define   PORT_PLL_M2_FRAC_MASK		0x3FFFFF
 /* PORT_PLL_3_A */

drivers/gpu/drm/i915/intel_ddi.c

@@ -1140,8 +1140,26 @@ static void hsw_ddi_clock_get(struct intel_encoder *encoder,
 static int bxt_calc_pll_link(struct drm_i915_private *dev_priv,
 				enum intel_dpll_id dpll)
 {
-	/* FIXME formula not available in bspec */
-	return 0;
+	struct intel_shared_dpll *pll;
+	struct intel_dpll_hw_state *state;
+	intel_clock_t clock;
+
+	/* For DDI ports we always use a shared PLL. */
+	if (WARN_ON(dpll == DPLL_ID_PRIVATE))
+		return 0;
+
+	pll = &dev_priv->shared_dplls[dpll];
+	state = &pll->config.hw_state;
+
+	clock.m1 = 2;
+	clock.m2 = (state->pll0 & PORT_PLL_M2_MASK) << 22;
+	if (state->pll3 & PORT_PLL_M2_FRAC_ENABLE)
+		clock.m2 |= state->pll2 & PORT_PLL_M2_FRAC_MASK;
+	clock.n = (state->pll1 & PORT_PLL_N_MASK) >> PORT_PLL_N_SHIFT;
+	clock.p1 = (state->ebb0 & PORT_PLL_P1_MASK) >> PORT_PLL_P1_SHIFT;
+	clock.p2 = (state->ebb0 & PORT_PLL_P2_MASK) >> PORT_PLL_P2_SHIFT;
+
+	return chv_calc_dpll_params(100000, &clock);
 }
 
 static void bxt_ddi_clock_get(struct intel_encoder *encoder,