drm/i915: use the HDMI DDI buffer translations from VBT

We currently use the recommended values from BSpec, but the VBT
specifies the correct value to use for the hardware we have, so use
it. We also fall back to the recommended value in case we can't find
the VBT.

In addition, this code also provides some infrastructure to parse more
information about the DDI ports. There's a lot more information we
could extract and use in the future.

v2: - Move some code to init_vbt_defaults.
v3: - Rebase
    - Clarify the "DVO Port" matching code
v4: - Use I915_MAX_PORTS
    - Change the HAS_DDI checks
    - Replace DRM_ERROR with DRM_DEBUG_KMS

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 351e21a..963245a 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -42,7 +42,6 @@
 	0x80C30FFF, 0x000B0000,
 	0x00FFFFFF, 0x00040006,
 	0x80D75FFF, 0x000B0000,
-	0x00FFFFFF, 0x00040006		/* HDMI parameters */
 };
 
 static const u32 hsw_ddi_translations_fdi[] = {
@@ -55,7 +54,22 @@
 	0x00C30FFF, 0x001E0000,
 	0x00FFFFFF, 0x00060006,
 	0x00D75FFF, 0x001E0000,
-	0x00FFFFFF, 0x00040006		/* HDMI parameters */
+};
+
+static const u32 hsw_ddi_translations_hdmi[] = {
+				/* Idx	NT mV diff	T mV diff	db  */
+	0x00FFFFFF, 0x0006000E, /* 0:	400		400		0   */
+	0x00E79FFF, 0x000E000C, /* 1:	400		500		2   */
+	0x00D75FFF, 0x0005000A, /* 2:	400		600		3.5 */
+	0x00FFFFFF, 0x0005000A, /* 3:	600		600		0   */
+	0x00E79FFF, 0x001D0007, /* 4:	600		750		2   */
+	0x00D75FFF, 0x000C0004, /* 5:	600		900		3.5 */
+	0x00FFFFFF, 0x00040006, /* 6:	800		800		0   */
+	0x80E79FFF, 0x00030002, /* 7:	800		1000		2   */
+	0x00FFFFFF, 0x00140005, /* 8:	850		850		0   */
+	0x00FFFFFF, 0x000C0004, /* 9:	900		900		0   */
+	0x00FFFFFF, 0x001C0003, /* 10:	950		950		0   */
+	0x80FFFFFF, 0x00030002, /* 11:	1000		1000		0   */
 };
 
 enum port intel_ddi_get_encoder_port(struct intel_encoder *intel_encoder)
@@ -92,12 +106,18 @@
 	const u32 *ddi_translations = (port == PORT_E) ?
 		hsw_ddi_translations_fdi :
 		hsw_ddi_translations_dp;
+	int hdmi_level = dev_priv->vbt.ddi_port_info[port].hdmi_level_shift;
 
 	for (i = 0, reg = DDI_BUF_TRANS(port);
 	     i < ARRAY_SIZE(hsw_ddi_translations_fdi); i++) {
 		I915_WRITE(reg, ddi_translations[i]);
 		reg += 4;
 	}
+	/* Entry 9 is for HDMI: */
+	for (i = 0; i < 2; i++) {
+		I915_WRITE(reg, hsw_ddi_translations_hdmi[hdmi_level * 2 + i]);
+		reg += 4;
+	}
 }
 
 /* Program DDI buffers translations for DP. By default, program ports A-D in DP