Add transparent LVDS decoder driver.

A transparent LVDS decoder is a DRM bridge device that does not require
any configuration and converts LVDS input to digital CMOS/TTL parallel
data output.

Signed-off-by: Jacopo Mondi <jacopo+rene...@jmondi.org>
---
 drivers/gpu/drm/bridge/Kconfig        |   8 +++
 drivers/gpu/drm/bridge/Makefile       |   1 +
 drivers/gpu/drm/bridge/lvds-decoder.c | 129 ++++++++++++++++++++++++++++++++++
 3 files changed, 138 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/lvds-decoder.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 3b99d5a..e52a5af 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -32,6 +32,14 @@ config DRM_DUMB_VGA_DAC
        help
          Support for RGB to VGA DAC based bridges

+config DRM_LVDS_DECODER
+       tristate "Transparent LVDS to parallel decoder support"
+       depends on OF
+       select DRM_PANEL_BRIDGE
+       help
+         Support for transparent LVDS to parallel decoders that don't require
+         any configuration.
+
 config DRM_LVDS_ENCODER
        tristate "Transparent parallel to LVDS encoder support"
        depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 373eb28..edc2332 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
 obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
+obj-$(CONFIG_DRM_LVDS_DECODER) += lvds-decoder.o
 obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
 obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += 
megachips-stdpxxxx-ge-b850v3-fw.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
diff --git a/drivers/gpu/drm/bridge/lvds-decoder.c 
b/drivers/gpu/drm/bridge/lvds-decoder.c
new file mode 100644
index 0000000..319f4d5
--- /dev/null
+++ b/drivers/gpu/drm/bridge/lvds-decoder.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LVDS to parallel data DRM bridge driver.
+ *
+ * Copyright (C) 2018 Jacopo Mondi <jacopo+rene...@jmondi.org>
+ */
+
+#include <drm/drmP.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_panel.h>
+
+#include <linux/of_graph.h>
+
+struct lvds_decoder {
+       struct device *dev;
+
+       struct drm_bridge bridge;
+       struct drm_bridge *next;
+       struct drm_encoder *bridge_encoder;
+};
+
+static inline struct lvds_decoder *to_lvds_decoder(struct drm_bridge *bridge)
+{
+       return container_of(bridge, struct lvds_decoder, bridge);
+}
+
+static int lvds_decoder_attach(struct drm_bridge *bridge)
+{
+       struct lvds_decoder *lvds = to_lvds_decoder(bridge);
+
+       return drm_bridge_attach(bridge->encoder, lvds->next, bridge);
+}
+
+struct drm_bridge_funcs lvds_dec_bridge_func = {
+       .attach = lvds_decoder_attach,
+};
+
+static int lvds_decoder_parse_dt(struct lvds_decoder *lvds)
+{
+       struct device_node *lvds_output;
+       struct device_node *remote;
+       int ret = 0;
+
+       lvds_output = of_graph_get_endpoint_by_regs(lvds->dev->of_node, 1, -1);
+       if (!lvds_output) {
+               dev_err(lvds->dev, "Missing endpoint in Port@1\n");
+               return -ENODEV;
+       }
+
+       remote = of_graph_get_remote_port_parent(lvds_output);
+       if (!remote) {
+               dev_err(lvds->dev, "Endpoint in Port@1 unconnected\n");
+               ret = -ENODEV;
+               goto error_put_lvds_node;
+       }
+
+       if (!of_device_is_available(remote)) {
+               dev_err(lvds->dev, "Port@1 remote endpoint is disabled\n");
+               ret = -ENODEV;
+               goto error_put_remote_node;
+       }
+
+       lvds->next = of_drm_find_bridge(remote);
+       if (!lvds->next)
+               ret = -EPROBE_DEFER;
+
+error_put_remote_node:
+       of_node_put(remote);
+error_put_lvds_node:
+       of_node_put(lvds_output);
+
+       return ret;
+}
+
+static int lvds_decoder_probe(struct platform_device *pdev)
+{
+       struct lvds_decoder *lvds;
+       int ret;
+
+       lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
+       if (!lvds)
+               return -ENOMEM;
+
+       lvds->dev = &pdev->dev;
+       platform_set_drvdata(pdev, lvds);
+
+       ret = lvds_decoder_parse_dt(lvds);
+       if (ret)
+               return ret;
+
+       lvds->bridge.driver_private = lvds;
+       lvds->bridge.of_node = pdev->dev.of_node;
+       lvds->bridge.funcs = &lvds_dec_bridge_func;
+
+       drm_bridge_add(&lvds->bridge);
+
+       return 0;
+}
+
+static int lvds_decoder_remove(struct platform_device *pdev)
+{
+       struct lvds_decoder *lvds = platform_get_drvdata(pdev);
+
+       drm_bridge_remove(&lvds->bridge);
+
+       return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id lvds_decoder_match[] = {
+       { .compatible = "lvds-decoder", },
+       { },
+};
+MODULE_DEVICE_TABLE(of, lvds_decoder_match);
+#endif
+
+static struct platform_driver lvds_decoder_driver = {
+       .probe  = lvds_decoder_probe,
+       .remove = lvds_decoder_remove,
+       .driver = {
+               .name           = "lvds_decoder",
+               .of_match_table = lvds_decoder_match,
+       },
+};
+module_platform_driver(lvds_decoder_driver);
+
+MODULE_AUTHOR("Jacopo Mondi <jac...@jmondi.org>");
+MODULE_DESCRIPTION("Transparent LVDS to parallel data decoder");
+MODULE_LICENSE("GPL v2");
--
2.7.4

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