[RFC] drm/imx: parallel-display: add ddc support

[linux-kernel-dev at beckhoff.com]

From: Patrick Brünn <p.bruenn at beckhoff.com>

Add ddc-i2c-bus as an additional source to read edid.

If you convert the 24-bit parallel-display signal to DVI and combine it
with I2C, you can connect DVI-D displays to your imx powered devices. An
example for this setup is the CX9020 Embedded PC.

Signed-off-by: Patrick Brünn <p.bruenn at beckhoff.com>
---
 drivers/gpu/drm/imx/parallel-display.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
index b4deb9c..32b745a 100644
--- a/drivers/gpu/drm/imx/parallel-display.c
+++ b/drivers/gpu/drm/imx/parallel-display.c
@@ -15,6 +15,7 @@
 
 #include <linux/component.h>
 #include <linux/module.h>
+#include <linux/i2c.h>
 #include <drm/drmP.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_crtc_helper.h>
@@ -38,6 +39,7 @@ struct imx_parallel_display {
 	int mode_valid;
 	struct drm_display_mode mode;
 	struct drm_panel *panel;
+	struct i2c_adapter *ddc;
 };
 
 static enum drm_connector_status imx_pd_connector_detect(
@@ -52,6 +54,16 @@ static int imx_pd_connector_get_modes(struct drm_connector *connector)
 	struct device_node *np = imxpd->dev->of_node;
 	int num_modes = 0;
 
+	if (imxpd->ddc) {
+		kfree(imxpd->edid);
+		imxpd->edid = drm_get_edid(connector, imxpd->ddc);
+		drm_mode_connector_update_edid_property(connector, imxpd->edid);
+		num_modes = drm_add_edid_modes(connector, imxpd->edid);
+		if (num_modes > 0)
+			return num_modes;
+	}
+
+
 	if (imxpd->panel && imxpd->panel->funcs &&
 	    imxpd->panel->funcs->get_modes) {
 		num_modes = imxpd->panel->funcs->get_modes(imxpd->panel);
@@ -90,6 +102,16 @@ static int imx_pd_connector_get_modes(struct drm_connector *connector)
 	return num_modes;
 }
 
+static enum drm_mode_status imx_pd_connector_mode_valid(struct drm_connector *connector,
+							struct drm_display_mode *mode)
+{
+	static const int IMX53_MAX_PIXEL_CLOCK_KHZ = 170000;
+
+	if (mode->clock > IMX53_MAX_PIXEL_CLOCK_KHZ)
+		return MODE_CLOCK_HIGH;
+	return MODE_OK;
+}
+
 static struct drm_encoder *imx_pd_connector_best_encoder(
 		struct drm_connector *connector)
 {
@@ -153,6 +175,7 @@ static struct drm_connector_funcs imx_pd_connector_funcs = {
 
 static struct drm_connector_helper_funcs imx_pd_connector_helper_funcs = {
 	.get_modes = imx_pd_connector_get_modes,
+	.mode_valid = imx_pd_connector_mode_valid,
 	.best_encoder = imx_pd_connector_best_encoder,
 };
 
@@ -209,6 +232,7 @@ static int imx_pd_bind(struct device *dev, struct device *master, void *data)
 {
 	struct drm_device *drm = data;
 	struct device_node *np = dev->of_node;
+	struct device_node *ddc_node;
 	struct device_node *port;
 	const u8 *edidp;
 	struct imx_parallel_display *imxpd;
@@ -219,6 +243,12 @@ static int imx_pd_bind(struct device *dev, struct device *master, void *data)
 	if (!imxpd)
 		return -ENOMEM;
 
+	ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
+	if (ddc_node) {
+		imxpd->ddc = of_find_i2c_adapter_by_node(ddc_node);
+		of_node_put(ddc_node);
+	}
+
 	edidp = of_get_property(np, "edid", &imxpd->edid_len);
 	if (edidp)
 		imxpd->edid = kmemdup(edidp, imxpd->edid_len, GFP_KERNEL);
-- 
1.9.1