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Subject[PATCH v5 5/6] drm/tegra: output: rgb: Support LVDS encoder bridge
Date
Newer Tegra device-trees will specify a video output graph, which involves
LVDS encoder bridge. This patch adds support for the LVDS encoder bridge
to the RGB output, allowing us to model the display hardware properly.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/gpu/drm/tegra/rgb.c | 58 +++++++++++++++++++++++++++++++------
1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
index 0562a7eb793f..9a7024ec96bc 100644
--- a/drivers/gpu/drm/tegra/rgb.c
+++ b/drivers/gpu/drm/tegra/rgb.c
@@ -7,6 +7,7 @@
#include <linux/clk.h>

#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge_connector.h>
#include <drm/drm_panel.h>
#include <drm/drm_simple_kms_helper.h>

@@ -267,24 +268,63 @@ int tegra_dc_rgb_remove(struct tegra_dc *dc)
int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
{
struct tegra_output *output = dc->rgb;
+ struct drm_connector *connector;
int err;

if (!dc->rgb)
return -ENODEV;

- drm_connector_init(drm, &output->connector, &tegra_rgb_connector_funcs,
- DRM_MODE_CONNECTOR_LVDS);
- drm_connector_helper_add(&output->connector,
- &tegra_rgb_connector_helper_funcs);
- output->connector.dpms = DRM_MODE_DPMS_OFF;
-
drm_simple_encoder_init(drm, &output->encoder, DRM_MODE_ENCODER_LVDS);
drm_encoder_helper_add(&output->encoder,
&tegra_rgb_encoder_helper_funcs);

- drm_connector_attach_encoder(&output->connector,
- &output->encoder);
- drm_connector_register(&output->connector);
+ /*
+ * Tegra devices that have LVDS panel utilize LVDS encoder bridge
+ * for converting up to 28 LCD LVTTL lanes into 5/4 LVDS lanes that
+ * go to display panel's receiver.
+ *
+ * Encoder usually have a power-down control which needs to be enabled
+ * in order to transmit data to the panel. Historically devices that
+ * use an older device-tree version didn't model the bridge, assuming
+ * that encoder is turned ON by default, while today's DRM allows us
+ * to model LVDS encoder properly.
+ *
+ * Newer device-trees utilize LVDS encoder bridge, which provides
+ * us with a connector and handles the display panel.
+ *
+ * For older device-trees we fall back to our own connector and use
+ * nvidia,panel phandle.
+ */
+ if (output->bridge) {
+ err = drm_bridge_attach(&output->encoder, output->bridge,
+ NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+ if (err) {
+ dev_err(output->dev, "failed to attach bridge: %d\n",
+ err);
+ return err;
+ }
+
+ connector = drm_bridge_connector_init(drm, &output->encoder);
+ if (IS_ERR(connector)) {
+ dev_err(output->dev,
+ "failed to initialize bridge connector: %pe\n",
+ connector);
+ return PTR_ERR(connector);
+ }
+
+ drm_connector_attach_encoder(connector, &output->encoder);
+ } else {
+ drm_connector_init(drm, &output->connector,
+ &tegra_rgb_connector_funcs,
+ DRM_MODE_CONNECTOR_LVDS);
+ drm_connector_helper_add(&output->connector,
+ &tegra_rgb_connector_helper_funcs);
+ output->connector.dpms = DRM_MODE_DPMS_OFF;
+
+ drm_connector_attach_encoder(&output->connector,
+ &output->encoder);
+ drm_connector_register(&output->connector);
+ }

err = tegra_output_init(drm, output);
if (err < 0) {
--
2.26.0
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