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>

1 files changed, 77 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 33003b97f1f..2f434297246 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -583,6 +583,76 @@ parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 	dev_priv->vbt.dsi.panel_id = mipi->panel_id;
 }
 
+static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
+			   struct bdb_header *bdb)
+{
+	union child_device_config *it, *child = NULL;
+	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
+	uint8_t hdmi_level_shift;
+	int i, j;
+	/* Each DDI port can have more than one value on the "DVO Port" field,
+	 * so look for all the possible values for each port and abort if more
+	 * than one is found. */
+	int dvo_ports[][2] = {
+		{DVO_PORT_HDMIA, DVO_PORT_DPA},
+		{DVO_PORT_HDMIB, DVO_PORT_DPB},
+		{DVO_PORT_HDMIC, DVO_PORT_DPC},
+		{DVO_PORT_HDMID, DVO_PORT_DPD},
+		{DVO_PORT_CRT, -1 /* Port E can only be DVO_PORT_CRT */ },
+	};
+
+	/* Find the child device to use, abort if more than one found. */
+	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
+		it = dev_priv->vbt.child_dev + i;
+
+		for (j = 0; j < 2; j++) {
+			if (dvo_ports[port][j] == -1)
+				break;
+
+			if (it->common.dvo_port == dvo_ports[port][j]) {
+				if (child) {
+					DRM_DEBUG_KMS("More than one child device for port %c in VBT.\n",
+						      port_name(port));
+					return;
+				}
+				child = it;
+			}
+		}
+	}
+	if (!child)
+		return;
+
+	if (bdb->version >= 158) {
+		/* The VBT HDMI level shift values match the table we have. */
+		hdmi_level_shift = child->raw[7] & 0xF;
+		if (hdmi_level_shift < 0xC) {
+			DRM_DEBUG_KMS("VBT HDMI level shift for port %c: %d\n",
+				      port_name(port),
+				      hdmi_level_shift);
+			info->hdmi_level_shift = hdmi_level_shift;
+		}
+	}
+}
+
+static void parse_ddi_ports(struct drm_i915_private *dev_priv,
+			    struct bdb_header *bdb)
+{
+	struct drm_device *dev = dev_priv->dev;
+	enum port port;
+
+	if (!HAS_DDI(dev))
+		return;
+
+	if (!dev_priv->vbt.child_dev_num)
+		return;
+
+	if (bdb->version < 155)
+		return;
+
+	for (port = PORT_A; port < I915_MAX_PORTS; port++)
+		parse_ddi_port(dev_priv, port, bdb);
+}
+
 static void
 parse_device_mapping(struct drm_i915_private *dev_priv,
 		       struct bdb_header *bdb)
@@ -652,6 +722,7 @@ static void
 init_vbt_defaults(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = dev_priv->dev;
+	enum port port;
 
 	dev_priv->vbt.crt_ddc_pin = GMBUS_PORT_VGADDC;
 
@@ -670,6 +741,11 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
 	dev_priv->vbt.lvds_use_ssc = 1;
 	dev_priv->vbt.lvds_ssc_freq = intel_bios_ssc_frequency(dev, 1);
 	DRM_DEBUG_KMS("Set default to SSC at %dMHz\n", dev_priv->vbt.lvds_ssc_freq);
+
+	for (port = PORT_A; port < I915_MAX_PORTS; port++) {
+		/* Recommended BSpec default: 800mV 0dB. */
+		dev_priv->vbt.ddi_port_info[port].hdmi_level_shift = 6;
+	}
 }
 
 static int __init intel_no_opregion_vbt_callback(const struct dmi_system_id *id)
@@ -761,6 +837,7 @@ intel_parse_bios(struct drm_device *dev)
 	parse_driver_features(dev_priv, bdb);
 	parse_edp(dev_priv, bdb);
 	parse_mipi(dev_priv, bdb);
+	parse_ddi_ports(dev_priv, bdb);
 
 	if (bios)
 		pci_unmap_rom(pdev, bios);