--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (c) 2018 Jernej Skrabec <jernej.skrabec@siol.net> */
+
+#include <drm/drmP.h>
+
+#include <dt-bindings/clock/sun8i-tcon-top.h>
+
+#include <linux/bitfield.h>
+#include <linux/component.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of_graph.h>
+#include <linux/platform_device.h>
+
+#include "sun8i_tcon_top.h"
+
+static int sun8i_tcon_top_get_connected_ep_id(struct device_node *node,
+                                             int port_id)
+{
+       struct device_node *ep, *remote, *port;
+       struct of_endpoint endpoint;
+
+       port = of_graph_get_port_by_id(node, port_id);
+       if (!port)
+               return -ENOENT;
+
+       for_each_available_child_of_node(port, ep) {
+               remote = of_graph_get_remote_port_parent(ep);
+               if (!remote)
+                       continue;
+
+               if (of_device_is_available(remote)) {
+                       of_graph_parse_endpoint(ep, &endpoint);
+
+                       of_node_put(remote);
+
+                       return endpoint.id;
+               }
+
+               of_node_put(remote);
+       }
+
+       return -ENOENT;
+}
+
+static struct clk_hw *sun8i_tcon_top_register_gate(struct device *dev,
+                                                  struct clk *parent,
+                                                  void __iomem *regs,
+                                                  spinlock_t *lock,
+                                                  u8 bit, int name_index)
+{
+       const char *clk_name, *parent_name;
+       int ret;
+
+       parent_name = __clk_get_name(parent);
+       ret = of_property_read_string_index(dev->of_node,
+                                           "clock-output-names", name_index,
+                                           &clk_name);
+       if (ret)
+               return ERR_PTR(ret);
+
+       return clk_hw_register_gate(dev, clk_name, parent_name,
+                                   CLK_SET_RATE_PARENT,
+                                   regs + TCON_TOP_GATE_SRC_REG,
+                                   bit, 0, lock);
+};
+
+static int sun8i_tcon_top_bind(struct device *dev, struct device *master,
+                              void *data)
+{
+       struct platform_device *pdev = to_platform_device(dev);
+       struct clk *dsi, *tcon_tv0, *tcon_tv1, *tve0, *tve1;
+       struct clk_hw_onecell_data *clk_data;
+       struct sun8i_tcon_top *tcon_top;
+       bool mixer0_unused = false;
+       struct resource *res;
+       void __iomem *regs;
+       int ret, i, id;
+       u32 val;
+
+       tcon_top = devm_kzalloc(dev, sizeof(*tcon_top), GFP_KERNEL);
+       if (!tcon_top)
+               return -ENOMEM;
+
+       clk_data = devm_kzalloc(dev, sizeof(*clk_data) +
+                               sizeof(*clk_data->hws) * CLK_NUM,
+                               GFP_KERNEL);
+       if (!clk_data)
+               return -ENOMEM;
+       tcon_top->clk_data = clk_data;
+
+       spin_lock_init(&tcon_top->reg_lock);
+
+       tcon_top->rst = devm_reset_control_get(dev, NULL);
+       if (IS_ERR(tcon_top->rst)) {
+               dev_err(dev, "Couldn't get our reset line\n");
+               return PTR_ERR(tcon_top->rst);
+       }
+
+       tcon_top->bus = devm_clk_get(dev, "bus");
+       if (IS_ERR(tcon_top->bus)) {
+               dev_err(dev, "Couldn't get the bus clock\n");
+               return PTR_ERR(tcon_top->bus);
+       }
+
+       dsi = devm_clk_get(dev, "dsi");
+       if (IS_ERR(dsi)) {
+               dev_err(dev, "Couldn't get the dsi clock\n");
+               return PTR_ERR(dsi);
+       }
+
+       tcon_tv0 = devm_clk_get(dev, "tcon-tv0");
+       if (IS_ERR(tcon_tv0)) {
+               dev_err(dev, "Couldn't get the tcon-tv0 clock\n");
+               return PTR_ERR(tcon_tv0);
+       }
+
+       tcon_tv1 = devm_clk_get(dev, "tcon-tv1");
+       if (IS_ERR(tcon_tv1)) {
+               dev_err(dev, "Couldn't get the tcon-tv1 clock\n");
+               return PTR_ERR(tcon_tv1);
+       }
+
+       tve0 = devm_clk_get(dev, "tve0");
+       if (IS_ERR(tve0)) {
+               dev_err(dev, "Couldn't get the tve0 clock\n");
+               return PTR_ERR(tve0);
+       }
+
+       tve1 = devm_clk_get(dev, "tve1");
+       if (IS_ERR(tve1)) {
+               dev_err(dev, "Couldn't get the tve1 clock\n");
+               return PTR_ERR(tve1);
+       }
+
+       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       regs = devm_ioremap_resource(dev, res);
+       if (IS_ERR(regs))
+               return PTR_ERR(regs);
+
+       ret = reset_control_deassert(tcon_top->rst);
+       if (ret) {
+               dev_err(dev, "Could not deassert ctrl reset control\n");
+               return ret;
+       }
+
+       ret = clk_prepare_enable(tcon_top->bus);
+       if (ret) {
+               dev_err(dev, "Could not enable bus clock\n");
+               goto err_assert_reset;
+       }
+
+       val = 0;
+
+       /* check if HDMI mux output is connected */
+       if (sun8i_tcon_top_get_connected_ep_id(dev->of_node, 5) >= 0) {
+               /* find HDMI input endpoint id, if it is connected at all*/
+               id = sun8i_tcon_top_get_connected_ep_id(dev->of_node, 4);
+               if (id >= 0)
+                       val = FIELD_PREP(TCON_TOP_HDMI_SRC_MSK, id + 1);
+               else
+                       DRM_DEBUG_DRIVER("TCON TOP HDMI input is not connected\n");
+       } else {
+               DRM_DEBUG_DRIVER("TCON TOP HDMI output is not connected\n");
+       }
+
+       writel(val, regs + TCON_TOP_GATE_SRC_REG);
+
+       val = 0;
+
+       /* process mixer0 mux output */
+       id = sun8i_tcon_top_get_connected_ep_id(dev->of_node, 1);
+       if (id >= 0) {
+               val = FIELD_PREP(TCON_TOP_PORT_DE0_MSK, id);
+       } else {
+               DRM_DEBUG_DRIVER("TCON TOP mixer0 output is not connected\n");
+               mixer0_unused = true;
+       }
+
+       /* process mixer1 mux output */
+       id = sun8i_tcon_top_get_connected_ep_id(dev->of_node, 3);
+       if (id >= 0) {
+               val |= FIELD_PREP(TCON_TOP_PORT_DE1_MSK, id);
+
+               /*
+                * mixer0 mux has priority over mixer1 mux. We have to
+                * make sure mixer0 doesn't overtake TCON from mixer1.
+                */
+               if (mixer0_unused && id == 0)
+                       val |= FIELD_PREP(TCON_TOP_PORT_DE0_MSK, 1);
+       } else {
+               DRM_DEBUG_DRIVER("TCON TOP mixer1 output is not connected\n");
+       }
+
+       writel(val, regs + TCON_TOP_PORT_SEL_REG);
+
+       /*
+        * TCON TOP has two muxes, which select parent clock for each TCON TV
+        * channel clock. Parent could be either TCON TV or TVE clock. For now
+        * we leave this fixed to TCON TV, since TVE driver for R40 is not yet
+        * implemented. Once it is, graph needs to be traversed to determine
+        * if TVE is active on each TCON TV. If it is, mux should be switched
+        * to TVE clock parent.
+        */
+       clk_data->hws[CLK_TCON_TOP_TV0] =
+               sun8i_tcon_top_register_gate(dev, tcon_tv0, regs,
+                                            &tcon_top->reg_lock,
+                                            TCON_TOP_TCON_TV0_GATE, 0);
+
+       clk_data->hws[CLK_TCON_TOP_TV1] =
+               sun8i_tcon_top_register_gate(dev, tcon_tv1, regs,
+                                            &tcon_top->reg_lock,
+                                            TCON_TOP_TCON_TV1_GATE, 1);
+
+       clk_data->hws[CLK_TCON_TOP_DSI] =
+               sun8i_tcon_top_register_gate(dev, dsi, regs,
+                                            &tcon_top->reg_lock,
+                                            TCON_TOP_TCON_DSI_GATE, 2);
+
+       for (i = 0; i < CLK_NUM; i++)
+               if (IS_ERR(clk_data->hws[i])) {
+                       ret = PTR_ERR(clk_data->hws[i]);
+                       goto err_unregister_gates;
+               }
+
+       clk_data->num = CLK_NUM;
+
+       ret = of_clk_add_hw_provider(dev->of_node, of_clk_hw_onecell_get,
+                                    clk_data);
+       if (ret)
+               goto err_unregister_gates;
+
+       dev_set_drvdata(dev, tcon_top);
+
+       return 0;
+
+err_unregister_gates:
+       for (i = 0; i < CLK_NUM; i++)
+               if (clk_data->hws[i])
+                       clk_hw_unregister_gate(clk_data->hws[i]);
+       clk_disable_unprepare(tcon_top->bus);
+err_assert_reset:
+       reset_control_assert(tcon_top->rst);
+
+       return ret;
+}
+
+static void sun8i_tcon_top_unbind(struct device *dev, struct device *master,
+                                 void *data)
+{
+       struct sun8i_tcon_top *tcon_top = dev_get_drvdata(dev);
+       struct clk_hw_onecell_data *clk_data = tcon_top->clk_data;
+       int i;
+
+       of_clk_del_provider(dev->of_node);
+       for (i = 0; i < CLK_NUM; i++)
+               clk_hw_unregister_gate(clk_data->hws[i]);
+
+       clk_disable_unprepare(tcon_top->bus);
+       reset_control_assert(tcon_top->rst);
+}
+
+static const struct component_ops sun8i_tcon_top_ops = {
+       .bind   = sun8i_tcon_top_bind,
+       .unbind = sun8i_tcon_top_unbind,
+};
+
+static int sun8i_tcon_top_probe(struct platform_device *pdev)
+{
+       return component_add(&pdev->dev, &sun8i_tcon_top_ops);
+}
+
+static int sun8i_tcon_top_remove(struct platform_device *pdev)
+{
+       component_del(&pdev->dev, &sun8i_tcon_top_ops);
+
+       return 0;
+}
+
+/* sun4i_drv uses this list to check if a device node is a TCON TOP */
+const struct of_device_id sun8i_tcon_top_of_table[] = {
+       { .compatible = "allwinner,sun8i-r40-tcon-top" },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, sun8i_tcon_top_of_table);
+EXPORT_SYMBOL(sun8i_tcon_top_of_table);
+
+static struct platform_driver sun8i_tcon_top_platform_driver = {
+       .probe          = sun8i_tcon_top_probe,
+       .remove         = sun8i_tcon_top_remove,
+       .driver         = {
+               .name           = "sun8i-tcon-top",
+               .of_match_table = sun8i_tcon_top_of_table,
+       },
+};
+module_platform_driver(sun8i_tcon_top_platform_driver);
+
+MODULE_AUTHOR("Jernej Skrabec <jernej.skrabec@siol.net>");
+MODULE_DESCRIPTION("Allwinner R40 TCON TOP driver");
+MODULE_LICENSE("GPL");