In general, for MIPI DSI there are three ways to represent the
pipeline for an upstream bridge to find the connected downstream
panel or bridge.
1. Child panel or bridge as a conventional device tree child node.
2. Child panel or bridge as an OF-graph port node.
3. Child panel or bridge as an OF-graph ports node.
There are three different downstream panels or bridges that are
possible to connect an upstream DSI host bridge - DSI Panel,
DSI Bridge, and I2C-Configured DSI bridge.
An example of the downstream panel represented as a child node,
&dsi {
compatible = "samsung,exynos5433-mipi-dsi";
ports {
port@0 {
reg = <0>;
dsi_to_mic: endpoint {
remote-endpoint = <&mic_to_dsi>;
};
};
};
panel@0 {
reg = <0>;
};
};
An example of the downstream bridge represented as a port node,
&i2c4 {
bridge@2c {
compatible = "ti,sn65dsi84";
ports {
port@0 {
reg = <0>;
bridge_in_dsi: endpoint {
remote-endpoint = <&dsi_out_bridge>;
data-lanes = <1 2>;
};
};
port@2 {
reg = <2>;
bridge_out_panel: endpoint {
remote-endpoint = <&panel_out_bridge>;
};
};
};
};
};
&dsi {
compatible = "fsl,imx8mm-mipi-dsim";
port {
dsi_in_lcdif: endpoint@0 {
reg = <0>;
remote-endpoint = <&lcdif_out_dsi>;
};
dsi_out_bridge: endpoint@1 {
reg = <1>;
remote-endpoint = <&bridge_in_dsi>;
};
};
};
An example of the downstream bridge represented as a ports node,
&dsi {
compatible = "fsl,imx8mm-mipi-dsim";
ports {
port@0 {
reg = <0>;
dsi_in_lcdif: endpoint@0 {
reg = <0>;
remote-endpoint = <&lcdif_out_dsi>;
};
};
port@1 {
reg = <1>;
dsi_out_bridge: endpoint {
remote-endpoint = <&bridge_in_dsi>;
};
};
};
In, summary it is possible to represent all three downstream slaves
devices using OF-graph port or ports node however only DSI Panel and
DSI Bridge are possible but not possible to represent I2C-Configured
DSI bridge child nodes since I2C-Configure bridges are child of I2C
node, not upstream DSI host bridge and it is must represent them
endpoint port linking.
This indeed means, the OF-graph port or ports representation is
mandatory for I2C-Configured DSI bridges.
This patch tries to add an OF-graph port or ports representation
detection code on top of existing child node detection.
It is possible to replace the entire detection code using existing
drm_of helper drm_of_find_panel_or_bridge but it will break the
Exynos DSI since the pipeline doesn't support OF-graph port or ports
node.
Overall, this patch has a combination of child and OF-graph pipeline
detections in order to support the backward compatibility of Exynos
DSI child node and i.MX8M Mini/Nano/Plus OF-graph port or ports
node pipelines.
This is the first common DSI host bridge driver that needs to support
all possible downstream connection pipeline combinations.
Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
---
Changes for v15:
- droped from drm_of
- added in exynos dsi
- updated commit messages
Changes for v13, v12:
- none
Changes for v11:
- drop extra line
Changes for v10:
- new patch
drivers/gpu/drm/exynos/exynos_drm_dsi.c | 38 +++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
index df15501b1075..f44a5a702ad5 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
@@ -1470,18 +1470,52 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
struct device *dev = dsi->dev;
struct drm_encoder *encoder = &dsi->encoder;
struct drm_device *drm = encoder->dev;
+ struct device_node *np = dev->of_node;
+ struct device_node *remote;
struct drm_panel *panel;
int ret;
- panel = of_drm_find_panel(device->dev.of_node);
+ /**
+ * Devices can also be child nodes when we also control that device
+ * through the upstream device (ie, MIPI-DCS for a MIPI-DSI device).
+ *
+ * Lookup for a child node of the given parent that isn't either port
+ * or ports.
+ */
+ for_each_available_child_of_node(np, remote) {
+ if (of_node_name_eq(remote, "port") ||
+ of_node_name_eq(remote, "ports"))
+ continue;
+
+ goto of_find_panel_or_bridge;
+ }
+
+ /*
+ * of_graph_get_remote_node() produces a noisy error message if port
+ * node isn't found and the absence of the port is a legit case here,
+ * so at first we silently check whether graph presents in the
+ * device-tree node.
+ */
+ if (!of_graph_is_present(np))
+ return -ENODEV;
+
+ remote = of_graph_get_remote_node(np, 1, 0);
+
+of_find_panel_or_bridge:
+ if (!remote)
+ return -ENODEV;
+
+ panel = of_drm_find_panel(remote);
if (!IS_ERR(panel)) {
dsi->out_bridge = devm_drm_panel_bridge_add(dev, panel);
} else {
- dsi->out_bridge = of_drm_find_bridge(device->dev.of_node);
+ dsi->out_bridge = of_drm_find_bridge(remote);
if (!dsi->out_bridge)
dsi->out_bridge = ERR_PTR(-EINVAL);
}
+ of_node_put(remote);
+
if (IS_ERR(dsi->out_bridge)) {
ret = PTR_ERR(dsi->out_bridge);
DRM_DEV_ERROR(dev, "failed to find the bridge: %d\n", ret);
--
2.25.1
