drm/i915: Per-DDI I_boost override

An OEM may request increased I_boost beyond the recommended values
by specifying an I_boost value to be applied to all swing entries for
a port. These override values are specified in VBT.

v2: rebase and remove unused iboost_bit variable

Issue: VIZ-5676
Signed-off-by: Antti Koskipaa <antti.koskipaa@linux.intel.com>
Reviewed-by: David Weinehall <david.weinehall@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1429,6 +1429,9 @@ struct ddi_vbt_port_info {
 	uint8_t supports_dp:1;
 
 	uint8_t alternate_aux_channel;
+
+	uint8_t dp_boost_level;
+	uint8_t hdmi_boost_level;
 };
 
 enum psr_lines_to_wait {

drivers/gpu/drm/i915/intel_bios.c

@@ -886,6 +886,17 @@ parse_mipi(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 	memset(dev_priv->vbt.dsi.sequence, 0, sizeof(dev_priv->vbt.dsi.sequence));
 }
 
+static u8 translate_iboost(u8 val)
+{
+	static const u8 mapping[] = { 1, 3, 7 }; /* See VBT spec */
+
+	if (val >= ARRAY_SIZE(mapping)) {
+		DRM_DEBUG_KMS("Unsupported I_boost value found in VBT (%d), display may not work properly\n", val);
+		return 0;
+	}
+	return mapping[val];
+}
+
 static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
 			   const struct bdb_header *bdb)
 {
@@ -1001,6 +1012,16 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
 			      hdmi_level_shift);
 		info->hdmi_level_shift = hdmi_level_shift;
 	}
+
+	/* Parse the I_boost config for SKL and above */
+	if (bdb->version >= 196 && (child->common.flags_1 & IBOOST_ENABLE)) {
+		info->dp_boost_level = translate_iboost(child->common.iboost_level & 0xF);
+		DRM_DEBUG_KMS("VBT (e)DP boost level for port %c: %d\n",
+			      port_name(port), info->dp_boost_level);
+		info->hdmi_boost_level = translate_iboost(child->common.iboost_level >> 4);
+		DRM_DEBUG_KMS("VBT HDMI boost level for port %c: %d\n",
+			      port_name(port), info->hdmi_boost_level);
+	}
 }
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv,

drivers/gpu/drm/i915/intel_bios.h

@@ -231,6 +231,10 @@ struct old_child_dev_config {
 /* This one contains field offsets that are known to be common for all BDB
  * versions. Notice that the meaning of the contents contents may still change,
  * but at least the offsets are consistent. */
+
+/* Definitions for flags_1 */
+#define IBOOST_ENABLE (1<<3)
+
 struct common_child_dev_config {
 	u16 handle;
 	u16 device_type;
@@ -239,8 +243,13 @@ struct common_child_dev_config {
 	u8 not_common2[2];
 	u8 ddc_pin;
 	u16 edid_ptr;
+	u8 obsolete;
+	u8 flags_1;
+	u8 not_common3[13];
+	u8 iboost_level;
 } __packed;
 
+
 /* This field changes depending on the BDB version, so the most reliable way to
  * read it is by checking the BDB version and reading the raw pointer. */
 union child_device_config {

drivers/gpu/drm/i915/intel_ddi.c

@@ -440,6 +440,7 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 reg;
+	u32 iboost_bit = 0;
 	int i, n_hdmi_entries, n_dp_entries, n_edp_entries, hdmi_default_entry,
 	    size;
 	int hdmi_level = dev_priv->vbt.ddi_port_info[port].hdmi_level_shift;
@@ -466,6 +467,10 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
 		ddi_translations_hdmi =
 				skl_get_buf_trans_hdmi(dev, &n_hdmi_entries);
 		hdmi_default_entry = 8;
+		/* If we're boosting the current, set bit 31 of trans1 */
+		if (dev_priv->vbt.ddi_port_info[port].hdmi_boost_level ||
+		    dev_priv->vbt.ddi_port_info[port].dp_boost_level)
+			iboost_bit = 1<<31;
 	} else if (IS_BROADWELL(dev)) {
 		ddi_translations_fdi = bdw_ddi_translations_fdi;
 		ddi_translations_dp = bdw_ddi_translations_dp;
@@ -526,7 +531,7 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
 	}
 
 	for (i = 0, reg = DDI_BUF_TRANS(port); i < size; i++) {
-		I915_WRITE(reg, ddi_translations[i].trans1);
+		I915_WRITE(reg, ddi_translations[i].trans1 | iboost_bit);
 		reg += 4;
 		I915_WRITE(reg, ddi_translations[i].trans2);
 		reg += 4;
@@ -541,7 +546,7 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
 		hdmi_level = hdmi_default_entry;
 
 	/* Entry 9 is for HDMI: */
-	I915_WRITE(reg, ddi_translations_hdmi[hdmi_level].trans1);
+	I915_WRITE(reg, ddi_translations_hdmi[hdmi_level].trans1 | iboost_bit);
 	reg += 4;
 	I915_WRITE(reg, ddi_translations_hdmi[hdmi_level].trans2);
 	reg += 4;
@@ -2078,18 +2083,35 @@ static void skl_ddi_set_iboost(struct drm_device *dev, u32 level,
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	const struct ddi_buf_trans *ddi_translations;
 	uint8_t iboost;
+	uint8_t dp_iboost, hdmi_iboost;
 	int n_entries;
 	u32 reg;
 
+	/* VBT may override standard boost values */
+	dp_iboost = dev_priv->vbt.ddi_port_info[port].dp_boost_level;
+	hdmi_iboost = dev_priv->vbt.ddi_port_info[port].hdmi_boost_level;
+
 	if (type == INTEL_OUTPUT_DISPLAYPORT) {
-		ddi_translations = skl_get_buf_trans_dp(dev, &n_entries);
-		iboost = ddi_translations[port].i_boost;
+		if (dp_iboost) {
+			iboost = dp_iboost;
+		} else {
+			ddi_translations = skl_get_buf_trans_dp(dev, &n_entries);
+			iboost = ddi_translations[port].i_boost;
+		}
 	} else if (type == INTEL_OUTPUT_EDP) {
-		ddi_translations = skl_get_buf_trans_edp(dev, &n_entries);
-		iboost = ddi_translations[port].i_boost;
+		if (dp_iboost) {
+			iboost = dp_iboost;
+		} else {
+			ddi_translations = skl_get_buf_trans_edp(dev, &n_entries);
+			iboost = ddi_translations[port].i_boost;
+		}
 	} else if (type == INTEL_OUTPUT_HDMI) {
-		ddi_translations = skl_get_buf_trans_hdmi(dev, &n_entries);
-		iboost = ddi_translations[port].i_boost;
+		if (hdmi_iboost) {
+			iboost = hdmi_iboost;
+		} else {
+			ddi_translations = skl_get_buf_trans_hdmi(dev, &n_entries);
+			iboost = ddi_translations[port].i_boost;
+		}
 	} else {
 		return;
 	}