drm/i915: rewrite the LCPLL code

Right now, we're trying to enable LCPLL at every mode set, but we're
never disabling it. Also, we really don't want to be disabling LCPLL
since it requires a very complex disable/enable sequence. This
register should really be set by the BIOS and we shouldn't be touching
it. Still, let's try to check its value and print some errors in case
we find something wrong. We're also adding intel_ddi_get_cdclk_freq
which will be used later in other places.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -3456,6 +3456,9 @@
 #define GEN7_SQ_CHICKEN_MBCUNIT_CONFIG		0x9030
 #define  GEN7_SQ_CHICKEN_MBCUNIT_SQINTMOB	(1<<11)
 
+#define HSW_FUSE_STRAP		0x42014
+#define  HSW_CDCLK_LIMIT	(1 << 24)
+
 /* PCH */
 
 /* south display engine interrupt: IBX */
@@ -4531,8 +4534,11 @@
 #define LCPLL_CTL			0x130040
 #define  LCPLL_PLL_DISABLE		(1<<31)
 #define  LCPLL_PLL_LOCK			(1<<30)
+#define  LCPLL_CLK_FREQ_MASK		(3<<26)
+#define  LCPLL_CLK_FREQ_450		(0<<26)
 #define  LCPLL_CD_CLOCK_DISABLE		(1<<25)
 #define  LCPLL_CD2X_CLOCK_DISABLE	(1<<23)
+#define  LCPLL_CD_SOURCE_FCLK		(1<<21)
 
 /* Pipe WM_LINETIME - watermark line time */
 #define PIPE_WM_LINETIME_A		0x45270

drivers/gpu/drm/i915/intel_ddi.c

@@ -682,12 +682,6 @@ void intel_ddi_mode_set(struct drm_encoder *encoder,
 	DRM_DEBUG_KMS("WR PLL: %dKHz refresh rate with p=%d, n2=%d r2=%d\n",
 		      crtc->mode.clock, p, n2, r2);
 
-	/* Enable LCPLL if disabled */
-	temp = I915_READ(LCPLL_CTL);
-	if (temp & LCPLL_PLL_DISABLE)
-		I915_WRITE(LCPLL_CTL,
-				temp & ~LCPLL_PLL_DISABLE);
-
 	/* Configure WR PLL 1, program the correct divider values for
 	 * the desired frequency and wait for warmup */
 	I915_WRITE(WRPLL_CTL1,
@@ -817,3 +811,34 @@ void intel_disable_ddi(struct intel_encoder *encoder)
 
 	I915_WRITE(DDI_BUF_CTL(port), temp);
 }
+
+static int intel_ddi_get_cdclk_freq(struct drm_i915_private *dev_priv)
+{
+	if (I915_READ(HSW_FUSE_STRAP) & HSW_CDCLK_LIMIT)
+		return 450;
+	else if ((I915_READ(LCPLL_CTL) & LCPLL_CLK_FREQ_MASK) ==
+		 LCPLL_CLK_FREQ_450)
+		return 450;
+	else
+		return 540;
+}
+
+void intel_ddi_pll_init(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	uint32_t val = I915_READ(LCPLL_CTL);
+
+	/* The LCPLL register should be turned on by the BIOS. For now let's
+	 * just check its state and print errors in case something is wrong.
+	 * Don't even try to turn it on.
+	 */
+
+	DRM_DEBUG_KMS("CDCLK running at %dMHz\n",
+		      intel_ddi_get_cdclk_freq(dev_priv));
+
+	if (val & LCPLL_CD_SOURCE_FCLK)
+		DRM_ERROR("CDCLK source is not LCPLL\n");
+
+	if (val & LCPLL_PLL_DISABLE)
+		DRM_ERROR("LCPLL is disabled\n");
+}

drivers/gpu/drm/i915/intel_display.c

@@ -7477,6 +7477,12 @@ static const struct drm_crtc_funcs intel_crtc_funcs = {
 	.page_flip = intel_crtc_page_flip,
 };
 
+static void intel_cpu_pll_init(struct drm_device *dev)
+{
+	if (IS_HASWELL(dev))
+		intel_ddi_pll_init(dev);
+}
+
 static void intel_pch_pll_init(struct drm_device *dev)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
@@ -8085,6 +8091,7 @@ void intel_modeset_init(struct drm_device *dev)
 			DRM_DEBUG_KMS("plane %d init failed: %d\n", i, ret);
 	}
 
+	intel_cpu_pll_init(dev);
 	intel_pch_pll_init(dev);
 
 	/* Just disable it once at startup */

drivers/gpu/drm/i915/intel_drv.h

@@ -580,5 +580,6 @@ extern bool intel_ddi_get_hw_state(struct intel_encoder *encoder,
 extern void intel_ddi_mode_set(struct drm_encoder *encoder,
 				struct drm_display_mode *mode,
 				struct drm_display_mode *adjusted_mode);
+extern void intel_ddi_pll_init(struct drm_device *dev);
 
 #endif /* __INTEL_DRV_H__ */