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

[linux-kernel-...@beckhoff.com]

From: Patrick Brünn <p.bru...@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