drm/i915: extend lpt_enable_clkout_dp

Now it implements 3 different sequences from BSpec and also has
support for ULT.

v2: - Change IS_ULT checks for LPT-LP checks
    - Add check for LPT-LP + with_fdi (Ben)
    - Merge DBUFF0/GEN0 bit definitions since they're the same
      register (Ben)
    - DBUFF0 (1<<0) is Disable, not Enable
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -4942,7 +4942,8 @@
 #define  SBI_SSCAUXDIV6				0x0610
 #define   SBI_SSCAUXDIV_FINALDIV2SEL(x)		((x)<<4)
 #define  SBI_DBUFF0				0x2a00
-#define   SBI_DBUFF0_ENABLE			(1<<0)
+#define  SBI_GEN0				0x1f00
+#define   SBI_GEN0_CFG_BUFFENABLE_DISABLE	(1<<0)
 
 /* LPT PIXCLK_GATE */
 #define PIXCLK_GATE			0xC6020

drivers/gpu/drm/i915/intel_display.c

@@ -5263,11 +5263,23 @@ static void lpt_program_fdi_mphy(struct drm_i915_private *dev_priv)
 	intel_sbi_write(dev_priv, 0x21EC, tmp, SBI_MPHY);
 }
 
-/* Sequence to enable CLKOUT_DP for FDI usage and configure PCH FDI I/O. */
-static void lpt_enable_clkout_dp(struct drm_device *dev)
+/* Implements 3 different sequences from BSpec chapter "Display iCLK
+ * Programming" based on the parameters passed:
+ * - Sequence to enable CLKOUT_DP
+ * - Sequence to enable CLKOUT_DP without spread
+ * - Sequence to enable CLKOUT_DP for FDI usage and configure PCH FDI I/O
+ */
+static void lpt_enable_clkout_dp(struct drm_device *dev, bool with_spread,
+				 bool with_fdi)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	uint32_t tmp;
+	uint32_t reg, tmp;
+
+	if (WARN(with_fdi && !with_spread, "FDI requires downspread\n"))
+		with_spread = true;
+	if (WARN(dev_priv->pch_id == INTEL_PCH_LPT_LP_DEVICE_ID_TYPE &&
+		 with_fdi, "LP PCH doesn't have FDI\n"))
+		with_fdi = false;
 
 	mutex_lock(&dev_priv->dpio_lock);
 
@@ -5278,17 +5290,22 @@ static void lpt_enable_clkout_dp(struct drm_device *dev)
 
 	udelay(24);
 
+	if (with_spread) {
 		tmp = intel_sbi_read(dev_priv, SBI_SSCCTL, SBI_ICLK);
 		tmp &= ~SBI_SSCCTL_PATHALT;
 		intel_sbi_write(dev_priv, SBI_SSCCTL, tmp, SBI_ICLK);
 
+		if (with_fdi) {
 			lpt_reset_fdi_mphy(dev_priv);
 			lpt_program_fdi_mphy(dev_priv);
+		}
+	}
 
-	/* ULT uses SBI_GEN0, but ULT doesn't have VGA, so we don't care. */
-	tmp = intel_sbi_read(dev_priv, SBI_DBUFF0, SBI_ICLK);
-	tmp |= SBI_DBUFF0_ENABLE;
-	intel_sbi_write(dev_priv, SBI_DBUFF0, tmp, SBI_ICLK);
+	reg = (dev_priv->pch_id == INTEL_PCH_LPT_LP_DEVICE_ID_TYPE) ?
+	       SBI_GEN0 : SBI_DBUFF0;
+	tmp = intel_sbi_read(dev_priv, reg, SBI_ICLK);
+	tmp |= SBI_GEN0_CFG_BUFFENABLE_DISABLE;
+	intel_sbi_write(dev_priv, reg, tmp, SBI_ICLK);
 
 	mutex_unlock(&dev_priv->dpio_lock);
 }
@@ -5310,7 +5327,7 @@ static void lpt_init_pch_refclk(struct drm_device *dev)
 	if (!has_vga)
 		return;
 
-	lpt_enable_clkout_dp(dev);
+	lpt_enable_clkout_dp(dev, true, true);
 }
 
 /*