drm/imx: imx-ldb: Add DDC support

Add support for reading EDID over Display Data Channel. If no DDC
adapter is available, falls back to hardcoded EDID or display-timings
node as before.

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Akshay Bhat <akshay.bhat@timesys.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

1 files changed, 34 insertions, 8 deletions

diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index a58eee59550a..f506e8dd76cb 100644
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -59,6 +59,7 @@ struct imx_ldb_channel {
         struct drm_encoder encoder;
         struct drm_panel *panel;
         struct device_node *child;
+        struct i2c_adapter *ddc;
         int chno;
         void *edid;
         int edid_len;
@@ -107,6 +108,9 @@ static int imx_ldb_connector_get_modes(struct drm_connector *connector)
                         return num_modes;
         }
 
+        if (!imx_ldb_ch->edid && imx_ldb_ch->ddc)
+                imx_ldb_ch->edid = drm_get_edid(connector, imx_ldb_ch->ddc);
+
         if (imx_ldb_ch->edid) {
                 drm_mode_connector_update_edid_property(connector,
                                                         imx_ldb_ch->edid);
@@ -553,6 +557,7 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
 
         for_each_child_of_node(np, child) {
                 struct imx_ldb_channel *channel;
+                struct device_node *ddc_node;
                 struct device_node *port;
 
                 ret = of_property_read_u32(child, "reg", &i);
@@ -595,14 +600,34 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
                         }
                 }
 
-                edidp = of_get_property(child, "edid", &channel->edid_len);
-                if (edidp) {
-                        channel->edid = kmemdup(edidp, channel->edid_len,
-                                                GFP_KERNEL);
-                } else if (!channel->panel) {
-                        ret = of_get_drm_display_mode(child, &channel->mode, 0);
-                        if (!ret)
-                                channel->mode_valid = 1;
+                ddc_node = of_parse_phandle(child, "ddc-i2c-bus", 0);
+                if (ddc_node) {
+                        channel->ddc = of_find_i2c_adapter_by_node(ddc_node);
+                        of_node_put(ddc_node);
+                        if (!channel->ddc) {
+                                dev_warn(dev, "failed to get ddc i2c adapter\n");
+                                return -EPROBE_DEFER;
+                        }
+                }
+
+                if (!channel->ddc) {
+                        /* if no DDC available, fallback to hardcoded EDID */
+                        dev_dbg(dev, "no ddc available\n");
+
+                        edidp = of_get_property(child, "edid",
+                                                &channel->edid_len);
+                        if (edidp) {
+                                channel->edid = kmemdup(edidp,
+                                                        channel->edid_len,
+                                                        GFP_KERNEL);
+                        } else if (!channel->panel) {
+                                /* fallback to display-timings node */
+                                ret = of_get_drm_display_mode(child,
+                                                              &channel->mode,
+                                                              0);
+                                if (!ret)
+                                        channel->mode_valid = 1;
+                        }
                 }
 
                 channel->bus_format = of_get_bus_format(dev, child);
@@ -647,6 +672,7 @@ static void imx_ldb_unbind(struct device *dev, struct device *master,
                 channel->encoder.funcs->destroy(&channel->encoder);
 
                 kfree(channel->edid);
+                i2c_put_adapter(channel->ddc);
         }
 }