drm/i915/icl: compute the MG PLL registers

This implements the "MG PLL Programming" sequence from our spec. The
biggest problem was that the spec assumes real numbers, so we had to
adjust some numbers and calculations due to the fact that the Kernel
prefers to deal with integers.

I recommend grabbing some coffee, a pen and paper before reviewing
this patch.

v2:
 - Correctly identify DP encoders after upstream change.
 - Small checkpatch issues.
 - Rebase.
v3:
 - Try to impove the comment on the tdc_targetcnt calculation based on
   Manasi's feedback (Manasi).
 - Rebase.
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180328215803.13835-7-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -2535,11 +2535,232 @@ static enum intel_dpll_id icl_port_to_mg_pll_id(enum port port)
 	return port - PORT_C + DPLL_ID_ICL_MGPLL1;
 }
 
+static bool icl_mg_pll_find_divisors(int clock_khz, bool is_dp, bool use_ssc,
+				     uint32_t *target_dco_khz,
+				     struct intel_dpll_hw_state *state)
+{
+	uint32_t dco_min_freq, dco_max_freq;
+	int div1_vals[] = {7, 5, 3, 2};
+	unsigned int i;
+	int div2;
+
+	dco_min_freq = is_dp ? 8100000 : use_ssc ? 8000000 : 7992000;
+	dco_max_freq = is_dp ? 8100000 : 10000000;
+
+	for (i = 0; i < ARRAY_SIZE(div1_vals); i++) {
+		int div1 = div1_vals[i];
+
+		for (div2 = 10; div2 > 0; div2--) {
+			int dco = div1 * div2 * clock_khz * 5;
+			int a_divratio, tlinedrv, inputsel, hsdiv;
+
+			if (dco < dco_min_freq || dco > dco_max_freq)
+				continue;
+
+			if (div2 >= 2) {
+				a_divratio = is_dp ? 10 : 5;
+				tlinedrv = 2;
+			} else {
+				a_divratio = 5;
+				tlinedrv = 0;
+			}
+			inputsel = is_dp ? 0 : 1;
+
+			switch (div1) {
+			default:
+				MISSING_CASE(div1);
+			case 2:
+				hsdiv = 0;
+				break;
+			case 3:
+				hsdiv = 1;
+				break;
+			case 5:
+				hsdiv = 2;
+				break;
+			case 7:
+				hsdiv = 3;
+				break;
+			}
+
+			*target_dco_khz = dco;
+
+			state->mg_refclkin_ctl = MG_REFCLKIN_CTL_OD_2_MUX(1);
+
+			state->mg_clktop2_coreclkctl1 =
+				MG_CLKTOP2_CORECLKCTL1_A_DIVRATIO(a_divratio);
+
+			state->mg_clktop2_hsclkctl =
+				MG_CLKTOP2_HSCLKCTL_TLINEDRV_CLKSEL(tlinedrv) |
+				MG_CLKTOP2_HSCLKCTL_CORE_INPUTSEL(inputsel) |
+				MG_CLKTOP2_HSCLKCTL_HSDIV_RATIO(hsdiv) |
+				MG_CLKTOP2_HSCLKCTL_DSDIV_RATIO(div2);
+
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/*
+ * The specification for this function uses real numbers, so the math had to be
+ * adapted to integer-only calculation, that's why it looks so different.
+ */
 static bool icl_calc_mg_pll_state(struct intel_crtc_state *crtc_state,
 				  struct intel_encoder *encoder, int clock,
 				  struct intel_dpll_hw_state *pll_state)
 {
-	/* TODO */
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	int refclk_khz = dev_priv->cdclk.hw.ref;
+	uint32_t dco_khz, m1div, m2div_int, m2div_rem, m2div_frac;
+	uint32_t iref_ndiv, iref_trim, iref_pulse_w;
+	uint32_t prop_coeff, int_coeff;
+	uint32_t tdc_targetcnt, feedfwgain;
+	uint64_t ssc_stepsize, ssc_steplen, ssc_steplog;
+	uint64_t tmp;
+	bool use_ssc = false;
+	bool is_dp = !intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI);
+
+	if (!icl_mg_pll_find_divisors(clock, is_dp, use_ssc, &dco_khz,
+				      pll_state)) {
+		DRM_DEBUG_KMS("Failed to find divisors for clock %d\n", clock);
+		return false;
+	}
+
+	m1div = 2;
+	m2div_int = dco_khz / (refclk_khz * m1div);
+	if (m2div_int > 255) {
+		m1div = 4;
+		m2div_int = dco_khz / (refclk_khz * m1div);
+		if (m2div_int > 255) {
+			DRM_DEBUG_KMS("Failed to find mdiv for clock %d\n",
+				      clock);
+			return false;
+		}
+	}
+	m2div_rem = dco_khz % (refclk_khz * m1div);
+
+	tmp = (uint64_t)m2div_rem * (1 << 22);
+	do_div(tmp, refclk_khz * m1div);
+	m2div_frac = tmp;
+
+	switch (refclk_khz) {
+	case 19200:
+		iref_ndiv = 1;
+		iref_trim = 28;
+		iref_pulse_w = 1;
+		break;
+	case 24000:
+		iref_ndiv = 1;
+		iref_trim = 25;
+		iref_pulse_w = 2;
+		break;
+	case 38400:
+		iref_ndiv = 2;
+		iref_trim = 28;
+		iref_pulse_w = 1;
+		break;
+	default:
+		MISSING_CASE(refclk_khz);
+		return false;
+	}
+
+	/*
+	 * tdc_res = 0.000003
+	 * tdc_targetcnt = int(2 / (tdc_res * 8 * 50 * 1.1) / refclk_mhz + 0.5)
+	 *
+	 * The multiplication by 1000 is due to refclk MHz to KHz conversion. It
+	 * was supposed to be a division, but we rearranged the operations of
+	 * the formula to avoid early divisions so we don't multiply the
+	 * rounding errors.
+	 *
+	 * 0.000003 * 8 * 50 * 1.1 = 0.00132, also known as 132 / 100000, which
+	 * we also rearrange to work with integers.
+	 *
+	 * The 0.5 transformed to 5 results in a multiplication by 10 and the
+	 * last division by 10.
+	 */
+	tdc_targetcnt = (2 * 1000 * 100000 * 10 / (132 * refclk_khz) + 5) / 10;
+
+	/*
+	 * Here we divide dco_khz by 10 in order to allow the dividend to fit in
+	 * 32 bits. That's not a problem since we round the division down
+	 * anyway.
+	 */
+	feedfwgain = (use_ssc || m2div_rem > 0) ?
+		m1div * 1000000 * 100 / (dco_khz * 3 / 10) : 0;
+
+	if (dco_khz >= 9000000) {
+		prop_coeff = 5;
+		int_coeff = 10;
+	} else {
+		prop_coeff = 4;
+		int_coeff = 8;
+	}
+
+	if (use_ssc) {
+		tmp = (uint64_t)dco_khz * 47 * 32;
+		do_div(tmp, refclk_khz * m1div * 10000);
+		ssc_stepsize = tmp;
+
+		tmp = (uint64_t)dco_khz * 1000;
+		ssc_steplen = DIV_ROUND_UP_ULL(tmp, 32 * 2 * 32);
+	} else {
+		ssc_stepsize = 0;
+		ssc_steplen = 0;
+	}
+	ssc_steplog = 4;
+
+	pll_state->mg_pll_div0 = (m2div_rem > 0 ? MG_PLL_DIV0_FRACNEN_H : 0) |
+				  MG_PLL_DIV0_FBDIV_FRAC(m2div_frac) |
+				  MG_PLL_DIV0_FBDIV_INT(m2div_int);
+
+	pll_state->mg_pll_div1 = MG_PLL_DIV1_IREF_NDIVRATIO(iref_ndiv) |
+				 MG_PLL_DIV1_DITHER_DIV_2 |
+				 MG_PLL_DIV1_NDIVRATIO(1) |
+				 MG_PLL_DIV1_FBPREDIV(m1div);
+
+	pll_state->mg_pll_lf = MG_PLL_LF_TDCTARGETCNT(tdc_targetcnt) |
+			       MG_PLL_LF_AFCCNTSEL_512 |
+			       MG_PLL_LF_GAINCTRL(1) |
+			       MG_PLL_LF_INT_COEFF(int_coeff) |
+			       MG_PLL_LF_PROP_COEFF(prop_coeff);
+
+	pll_state->mg_pll_frac_lock = MG_PLL_FRAC_LOCK_TRUELOCK_CRIT_32 |
+				      MG_PLL_FRAC_LOCK_EARLYLOCK_CRIT_32 |
+				      MG_PLL_FRAC_LOCK_LOCKTHRESH(10) |
+				      MG_PLL_FRAC_LOCK_DCODITHEREN |
+				      MG_PLL_FRAC_LOCK_FEEDFWRDGAIN(feedfwgain);
+	if (use_ssc || m2div_rem > 0)
+		pll_state->mg_pll_frac_lock |= MG_PLL_FRAC_LOCK_FEEDFWRDCAL_EN;
+
+	pll_state->mg_pll_ssc = (use_ssc ? MG_PLL_SSC_EN : 0) |
+				MG_PLL_SSC_TYPE(2) |
+				MG_PLL_SSC_STEPLENGTH(ssc_steplen) |
+				MG_PLL_SSC_STEPNUM(ssc_steplog) |
+				MG_PLL_SSC_FLLEN |
+				MG_PLL_SSC_STEPSIZE(ssc_stepsize);
+
+	pll_state->mg_pll_tdc_coldst_bias = MG_PLL_TDC_COLDST_COLDSTART;
+
+	if (refclk_khz != 38400) {
+		pll_state->mg_pll_tdc_coldst_bias |=
+			MG_PLL_TDC_COLDST_IREFINT_EN |
+			MG_PLL_TDC_COLDST_REFBIAS_START_PULSE_W(iref_pulse_w) |
+			MG_PLL_TDC_COLDST_COLDSTART |
+			MG_PLL_TDC_TDCOVCCORR_EN |
+			MG_PLL_TDC_TDCSEL(3);
+
+		pll_state->mg_pll_bias = MG_PLL_BIAS_BIAS_GB_SEL(3) |
+					 MG_PLL_BIAS_INIT_DCOAMP(0x3F) |
+					 MG_PLL_BIAS_BIAS_BONUS(10) |
+					 MG_PLL_BIAS_BIASCAL_EN |
+					 MG_PLL_BIAS_CTRIM(12) |
+					 MG_PLL_BIAS_VREF_RDAC(4) |
+					 MG_PLL_BIAS_IREFTRIM(iref_trim);
+	}
+
 	return true;
 }