drm/i915: Simplify i830 DVO 2x clock handling

Let's just always enable the DVO 2x clock on i830. This way we don't
have to track if DVO is being used or not. The spec does suggest we
should disable the clock when it isn't needed, but this does appear
to work just fine.

This removes another crtc->config usage.

v2: Split the DPLL enable sequence change to a separate patch

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190305192400.23121-2-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -1441,19 +1441,6 @@ static void chv_enable_pll(struct intel_crtc *crtc,
 	}
 }
 
-static int intel_num_dvo_pipes(struct drm_i915_private *dev_priv)
-{
-	struct intel_crtc *crtc;
-	int count = 0;
-
-	for_each_intel_crtc(&dev_priv->drm, crtc) {
-		count += crtc->base.state->active &&
-			intel_crtc_has_type(crtc->config, INTEL_OUTPUT_DVO);
-	}
-
-	return count;
-}
-
 static void i9xx_enable_pll(struct intel_crtc *crtc,
 			    const struct intel_crtc_state *crtc_state)
 {
@@ -1468,19 +1455,6 @@ static void i9xx_enable_pll(struct intel_crtc *crtc,
 	if (IS_MOBILE(dev_priv) && !IS_I830(dev_priv))
 		assert_panel_unlocked(dev_priv, crtc->pipe);
 
-	/* Enable DVO 2x clock on both PLLs if necessary */
-	if (IS_I830(dev_priv) && intel_num_dvo_pipes(dev_priv) > 0) {
-		/*
-		 * It appears to be important that we don't enable this
-		 * for the current pipe before otherwise configuring the
-		 * PLL. No idea how this should be handled if multiple
-		 * DVO outputs are enabled simultaneosly.
-		 */
-		dpll |= DPLL_DVO_2X_MODE;
-		I915_WRITE(DPLL(!crtc->pipe),
-			   I915_READ(DPLL(!crtc->pipe)) | DPLL_DVO_2X_MODE);
-	}
-
 	/*
 	 * Apparently we need to have VGA mode enabled prior to changing
 	 * the P1/P2 dividers. Otherwise the DPLL will keep using the old
@@ -1519,16 +1493,6 @@ static void i9xx_disable_pll(const struct intel_crtc_state *crtc_state)
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	enum pipe pipe = crtc->pipe;
 
-	/* Disable DVO 2x clock on both PLLs if necessary */
-	if (IS_I830(dev_priv) &&
-	    intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DVO) &&
-	    !intel_num_dvo_pipes(dev_priv)) {
-		I915_WRITE(DPLL(PIPE_B),
-			   I915_READ(DPLL(PIPE_B)) & ~DPLL_DVO_2X_MODE);
-		I915_WRITE(DPLL(PIPE_A),
-			   I915_READ(DPLL(PIPE_A)) & ~DPLL_DVO_2X_MODE);
-	}
-
 	/* Don't disable pipe or pipe PLLs if needed */
 	if (IS_I830(dev_priv))
 		return;
@@ -7493,7 +7457,19 @@ static void i8xx_compute_dpll(struct intel_crtc *crtc,
 			dpll |= PLL_P2_DIVIDE_BY_4;
 	}
 
-	if (!IS_I830(dev_priv) &&
+	/*
+	 * Bspec:
+	 * "[Almador Errata}: For the correct operation of the muxed DVO pins
+	 *  (GDEVSELB/I2Cdata, GIRDBY/I2CClk) and (GFRAMEB/DVI_Data,
+	 *  GTRDYB/DVI_Clk): Bit 31 (DPLL VCO Enable) and Bit 30 (2X Clock
+	 *  Enable) must be set to “1” in both the DPLL A Control Register
+	 *  (06014h-06017h) and DPLL B Control Register (06018h-0601Bh)."
+	 *
+	 * For simplicity We simply keep both bits always enabled in
+	 * both DPLLS. The spec says we should disable the DVO 2X clock
+	 * when not needed, but this seems to work fine in practice.
+	 */
+	if (IS_I830(dev_priv) ||
 	    intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DVO))
 		dpll |= DPLL_DVO_2X_MODE;
 
@@ -8217,14 +8193,6 @@ static bool i9xx_get_pipe_config(struct intel_crtc *crtc,
 	}
 	pipe_config->dpll_hw_state.dpll = I915_READ(DPLL(crtc->pipe));
 	if (!IS_VALLEYVIEW(dev_priv) && !IS_CHERRYVIEW(dev_priv)) {
-		/*
-		 * DPLL_DVO_2X_MODE must be enabled for both DPLLs
-		 * on 830. Filter it out here so that we don't
-		 * report errors due to that.
-		 */
-		if (IS_I830(dev_priv))
-			pipe_config->dpll_hw_state.dpll &= ~DPLL_DVO_2X_MODE;
-
 		pipe_config->dpll_hw_state.fp0 = I915_READ(FP0(crtc->pipe));
 		pipe_config->dpll_hw_state.fp1 = I915_READ(FP1(crtc->pipe));
 	} else {
@@ -15616,7 +15584,7 @@ void i830_enable_pipe(struct drm_i915_private *dev_priv, enum pipe pipe)
 		      pipe_name(pipe), clock.vco, clock.dot);
 
 	fp = i9xx_dpll_compute_fp(&clock);
-	dpll = (I915_READ(DPLL(pipe)) & DPLL_DVO_2X_MODE) |
+	dpll = DPLL_DVO_2X_MODE |
 		DPLL_VGA_MODE_DIS |
 		((clock.p1 - 2) << DPLL_FPA01_P1_POST_DIV_SHIFT) |
 		PLL_P2_DIVIDE_BY_4 |