Some boards have an entirely passive RGB to VGA bridge, based on either
DACs or resistor ladders.
Those might or might not have an i2c bus routed to the VGA connector in
order to access the screen EDIDs.
Add a bridge that doesn't do anything but expose the modes available on the
screen, either based on the EDIDs if available, or based on the XGA
standards.
Acked-by: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
Documentation/devicetree/bindings/display/bridge/simple-vga-dac.txt | 48 +++++++++++++++-
drivers/gpu/drm/bridge/Kconfig | 7 ++-
drivers/gpu/drm/bridge/Makefile | 1 +-
drivers/gpu/drm/bridge/simple-vga-dac.c | 229 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 285 insertions(+), 0 deletions(-)
create mode 100644 Documentation/devicetree/bindings/display/bridge/simple-vga-dac.txt
create mode 100644 drivers/gpu/drm/bridge/simple-vga-dac.c
diff --git a/Documentation/devicetree/bindings/display/bridge/simple-vga-dac.txt b/Documentation/devicetree/bindings/display/bridge/simple-vga-dac.txt
new file mode 100644
index 000000000000..7143c54ea88c
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/simple-vga-dac.txt
@@ -0,0 +1,48 @@
+Dumb RGB to VGA bridge
+----------------------
+
+This binding is aimed for dumb RGB to VGA bridges that do not require
+any configuration.
+
+Required properties:
+
+- compatible: Must be "simple-vga-dac"
+
+Required nodes:
+
+This device has two video ports. Their connections are modeled using the OF
+graph bindings specified in Documentation/devicetree/bindings/graph.txt.
+
+- Video port 0 for RGB input
+- Video port 1 for VGA output
+
+
+Example
+-------
+
+bridge {
+ compatible = "simple-vga-dac";
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ ports {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ port@0 {
+ reg = <0>;
+
+ vga_bridge_in: endpoint {
+ remote-endpoint = <&tcon0_out_vga>;
+ };
+ };
+
+ port@1 {
+ reg = <1>;
+
+ vga_bridge_out: endpoint {
+ remote-endpoint = <&vga_con_in>;
+ };
+ };
+ };
+};
diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index b590e678052d..5fe8c7829052 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -58,6 +58,13 @@ config DRM_SII902X
---help---
Silicon Image sii902x bridge chip driver.
+config DRM_SIMPLE_VGA_DAC
+ tristate "Simple VGA DAC support"
+ depends on OF
+ select DRM_KMS_HELPER
+ ---help---
+ Support for RGB to VGA bridges
+
config DRM_TOSHIBA_TC358767
tristate "Toshiba TC358767 eDP bridge"
depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index efdb07e878f5..2cdd99035f38 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
obj-$(CONFIG_DRM_SII902X) += sii902x.o
+obj-$(CONFIG_DRM_SIMPLE_VGA_DAC) += simple-vga-dac.o
obj-$(CONFIG_DRM_TOSHIBA_TC358767) += tc358767.o
obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix/
obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
diff --git a/drivers/gpu/drm/bridge/simple-vga-dac.c b/drivers/gpu/drm/bridge/simple-vga-dac.c
new file mode 100644
index 000000000000..c81a25ab0b0d
--- /dev/null
+++ b/drivers/gpu/drm/bridge/simple-vga-dac.c
@@ -0,0 +1,229 @@
+/*
+ * Copyright (C) 2015-2016 Free Electrons
+ * Copyright (C) 2015-2016 NextThing Co
+ *
+ * Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/of_graph.h>
+
+#include <drm/drmP.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_crtc_helper.h>
+
+struct simple_vga {
+ struct drm_bridge bridge;
+ struct drm_connector connector;
+
+ struct i2c_adapter *ddc;
+};
+
+static inline struct simple_vga *
+drm_bridge_to_simple_vga(struct drm_bridge *bridge)
+{
+ return container_of(bridge, struct simple_vga, bridge);
+}
+
+static inline struct simple_vga *
+drm_connector_to_simple_vga(struct drm_connector *connector)
+{
+ return container_of(connector, struct simple_vga, connector);
+}
+
+static int simple_vga_get_modes(struct drm_connector *connector)
+{
+ struct simple_vga *vga = drm_connector_to_simple_vga(connector);
+ struct edid *edid;
+ int ret;
+
+ if (IS_ERR(vga->ddc))
+ goto fallback;
+
+ edid = drm_get_edid(connector, vga->ddc);
+ if (!edid) {
+ DRM_INFO("EDID readout failed, falling back to standard modes\n");
+ goto fallback;
+ }
+
+ drm_mode_connector_update_edid_property(connector, edid);
+ return drm_add_edid_modes(connector, edid);
+
+fallback:
+ /*
+ * In case we cannot retrieve the EDIDs (broken or missing i2c
+ * bus), fallback on the XGA standards
+ */
+ ret = drm_add_modes_noedid(connector, 1920, 1200);
+
+ /* And prefer a mode pretty much anyone can handle */
+ drm_set_preferred_mode(connector, 1024, 768);
+
+ return ret;
+}
+
+static const struct drm_connector_helper_funcs simple_vga_con_helper_funcs = {
+ .get_modes = simple_vga_get_modes,
+};
+
+static enum drm_connector_status
+simple_vga_connector_detect(struct drm_connector *connector, bool force)
+{
+ struct simple_vga *vga = drm_connector_to_simple_vga(connector);
+
+ /*
+ * Even if we have an I2C bus, we can't assume that the cable
+ * is disconnected if drm_probe_ddc fails. Some cables don't
+ * wire the DDC pins, or the I2C bus might not be working at
+ * all.
+ */
+ if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
+ return connector_status_connected;
+
+ return connector_status_unknown;
+}
+
+static void
+simple_vga_connector_destroy(struct drm_connector *connector)
+{
+ drm_connector_cleanup(connector);
+}
+
+static const struct drm_connector_funcs simple_vga_con_funcs = {
+ .dpms = drm_atomic_helper_connector_dpms,
+ .detect = simple_vga_connector_detect,
+ .fill_modes = drm_helper_probe_single_connector_modes,
+ .destroy = simple_vga_connector_destroy,
+ .reset = drm_atomic_helper_connector_reset,
+ .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+ .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static int simple_vga_attach(struct drm_bridge *bridge)
+{
+ struct simple_vga *vga = drm_bridge_to_simple_vga(bridge);
+ int ret;
+
+ if (!bridge->encoder) {
+ DRM_ERROR("Missing encoder\n");
+ return -ENODEV;
+ }
+
+ drm_connector_helper_add(&vga->connector,
+ &simple_vga_con_helper_funcs);
+ ret = drm_connector_init(bridge->dev, &vga->connector,
+ &simple_vga_con_funcs, DRM_MODE_CONNECTOR_VGA);
+ if (ret) {
+ DRM_ERROR("Failed to initialize connector\n");
+ return ret;
+ }
+
+ drm_mode_connector_attach_encoder(&vga->connector,
+ bridge->encoder);
+
+ return 0;
+}
+
+static const struct drm_bridge_funcs simple_vga_bridge_funcs = {
+ .attach = simple_vga_attach,
+};
+
+static struct i2c_adapter *simple_vga_retrieve_ddc(struct device *dev)
+{
+ struct device_node *end_node, *phandle, *remote;
+ struct i2c_adapter *ddc;
+
+ end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
+ if (!end_node) {
+ dev_err(dev, "Missing connector endpoint\n");
+ return ERR_PTR(-ENODEV);
+ }
+
+ remote = of_graph_get_remote_port_parent(end_node);
+ of_node_put(end_node);
+ if (!remote) {
+ dev_err(dev, "Enable to parse remote node\n");
+ return ERR_PTR(-EINVAL);
+ }
+
+ phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
+ of_node_put(remote);
+ if (!phandle)
+ return ERR_PTR(-ENODEV);
+
+ ddc = of_get_i2c_adapter_by_node(phandle);
+ of_node_put(phandle);
+ if (!ddc)
+ return ERR_PTR(-EPROBE_DEFER);
+
+ return ddc;
+}
+
+static int simple_vga_probe(struct platform_device *pdev)
+{
+ struct simple_vga *vga;
+ int ret;
+
+ vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
+ if (!vga)
+ return -ENOMEM;
+ platform_set_drvdata(pdev, vga);
+
+ vga->ddc = simple_vga_retrieve_ddc(&pdev->dev);
+ if (IS_ERR(vga->ddc)) {
+ if (PTR_ERR(vga->ddc) == -ENODEV) {
+ dev_info(&pdev->dev,
+ "No i2c bus specified... Disabling EDID readout\n");
+ } else {
+ dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
+ return PTR_ERR(vga->ddc);
+ }
+ }
+
+ vga->bridge.funcs = &simple_vga_bridge_funcs;
+ vga->bridge.of_node = pdev->dev.of_node;
+
+ ret = drm_bridge_add(&vga->bridge);
+ if (ret && !IS_ERR(vga->ddc))
+ i2c_put_adapter(vga->ddc);
+
+ return ret;
+}
+
+static int simple_vga_remove(struct platform_device *pdev)
+{
+ struct simple_vga *vga = platform_get_drvdata(pdev);
+
+ drm_bridge_remove(&vga->bridge);
+
+ if (!IS_ERR(vga->ddc))
+ i2c_put_adapter(vga->ddc);
+
+ return 0;
+}
+
+static const struct of_device_id simple_vga_match[] = {
+ { .compatible = "simple-vga-dac" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, simple_vga_match);
+
+struct platform_driver simple_vga_driver = {
+ .probe = simple_vga_probe,
+ .remove = simple_vga_remove,
+ .driver = {
+ .name = "simple-vga-dac",
+ .of_match_table = simple_vga_match,
+ },
+};
+module_platform_driver(simple_vga_driver);
+
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Simple VGA DAC driver");
+MODULE_LICENSE("GPL");
--
git-series 0.8.10
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