drivers/gpu/drm/bridge/dumb-vga-dac.c

   1 /*
   2  * Copyright (C) 2015-2016 Free Electrons
   3  * Copyright (C) 2015-2016 NextThing Co
   4  *
   5  * Maxime Ripard <maxime.ripard@free-electrons.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2 of
  10  * the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/of_graph.h>
  15
  16 #include <drm/drmP.h>
  17 #include <drm/drm_atomic_helper.h>
  18 #include <drm/drm_crtc.h>
  19 #include <drm/drm_crtc_helper.h>
  20
  21 struct dumb_vga {
  22         struct drm_bridge       bridge;
  23         struct drm_connector    connector;
  24
  25         struct i2c_adapter      *ddc;
  26 };
  27
  28 static inline struct dumb_vga *
  29 drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
  30 {
  31         return container_of(bridge, struct dumb_vga, bridge);
  32 }
  33
  34 static inline struct dumb_vga *
  35 drm_connector_to_dumb_vga(struct drm_connector *connector)
  36 {
  37         return container_of(connector, struct dumb_vga, connector);
  38 }
  39
  40 static int dumb_vga_get_modes(struct drm_connector *connector)
  41 {
  42         struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
  43         struct edid *edid;
  44         int ret;
  45
  46         if (IS_ERR(vga->ddc))
  47                 goto fallback;
  48
  49         edid = drm_get_edid(connector, vga->ddc);
  50         if (!edid) {
  51                 DRM_INFO("EDID readout failed, falling back to standard modes\n");
  52                 goto fallback;
  53         }
  54
  55         drm_mode_connector_update_edid_property(connector, edid);
  56         ret = drm_add_edid_modes(connector, edid);
  57         kfree(edid);
  58         return ret;
  59
  60 fallback:
  61         /*
  62          * In case we cannot retrieve the EDIDs (broken or missing i2c
  63          * bus), fallback on the XGA standards
  64          */
  65         ret = drm_add_modes_noedid(connector, 1920, 1200);
  66
  67         /* And prefer a mode pretty much anyone can handle */
  68         drm_set_preferred_mode(connector, 1024, 768);
  69
  70         return ret;
  71 }
  72
  73 static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
  74         .get_modes      = dumb_vga_get_modes,
  75 };
  76
  77 static enum drm_connector_status
  78 dumb_vga_connector_detect(struct drm_connector *connector, bool force)
  79 {
  80         struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
  81
  82         /*
  83          * Even if we have an I2C bus, we can't assume that the cable
  84          * is disconnected if drm_probe_ddc fails. Some cables don't
  85          * wire the DDC pins, or the I2C bus might not be working at
  86          * all.
  87          */
  88         if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
  89                 return connector_status_connected;
  90
  91         return connector_status_unknown;
  92 }
  93
  94 static const struct drm_connector_funcs dumb_vga_con_funcs = {
  95         .dpms                   = drm_atomic_helper_connector_dpms,
  96         .detect                 = dumb_vga_connector_detect,
  97         .fill_modes             = drm_helper_probe_single_connector_modes,
  98         .destroy                = drm_connector_cleanup,
  99         .reset                  = drm_atomic_helper_connector_reset,
 100         .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
 101         .atomic_destroy_state   = drm_atomic_helper_connector_destroy_state,
 102 };
 103
 104 static int dumb_vga_attach(struct drm_bridge *bridge)
 105 {
 106         struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
 107         int ret;
 108
 109         if (!bridge->encoder) {
 110                 DRM_ERROR("Missing encoder\n");
 111                 return -ENODEV;
 112         }
 113
 114         drm_connector_helper_add(&vga->connector,
 115                                  &dumb_vga_con_helper_funcs);
 116         ret = drm_connector_init(bridge->dev, &vga->connector,
 117                                  &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA);
 118         if (ret) {
 119                 DRM_ERROR("Failed to initialize connector\n");
 120                 return ret;
 121         }
 122
 123         drm_mode_connector_attach_encoder(&vga->connector,
 124                                           bridge->encoder);
 125
 126         return 0;
 127 }
 128
 129 static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
 130         .attach         = dumb_vga_attach,
 131 };
 132
 133 static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
 134 {
 135         struct device_node *end_node, *phandle, *remote;
 136         struct i2c_adapter *ddc;
 137
 138         end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
 139         if (!end_node) {
 140                 dev_err(dev, "Missing connector endpoint\n");
 141                 return ERR_PTR(-ENODEV);
 142         }
 143
 144         remote = of_graph_get_remote_port_parent(end_node);
 145         of_node_put(end_node);
 146         if (!remote) {
 147                 dev_err(dev, "Enable to parse remote node\n");
 148                 return ERR_PTR(-EINVAL);
 149         }
 150
 151         phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
 152         of_node_put(remote);
 153         if (!phandle)
 154                 return ERR_PTR(-ENODEV);
 155
 156         ddc = of_get_i2c_adapter_by_node(phandle);
 157         of_node_put(phandle);
 158         if (!ddc)
 159                 return ERR_PTR(-EPROBE_DEFER);
 160
 161         return ddc;
 162 }
 163
 164 static int dumb_vga_probe(struct platform_device *pdev)
 165 {
 166         struct dumb_vga *vga;
 167         int ret;
 168
 169         vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
 170         if (!vga)
 171                 return -ENOMEM;
 172         platform_set_drvdata(pdev, vga);
 173
 174         vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
 175         if (IS_ERR(vga->ddc)) {
 176                 if (PTR_ERR(vga->ddc) == -ENODEV) {
 177                         dev_dbg(&pdev->dev,
 178                                 "No i2c bus specified. Disabling EDID readout\n");
 179                 } else {
 180                         dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
 181                         return PTR_ERR(vga->ddc);
 182                 }
 183         }
 184
 185         vga->bridge.funcs = &dumb_vga_bridge_funcs;
 186         vga->bridge.of_node = pdev->dev.of_node;
 187
 188         ret = drm_bridge_add(&vga->bridge);
 189         if (ret && !IS_ERR(vga->ddc))
 190                 i2c_put_adapter(vga->ddc);
 191
 192         return ret;
 193 }
 194
 195 static int dumb_vga_remove(struct platform_device *pdev)
 196 {
 197         struct dumb_vga *vga = platform_get_drvdata(pdev);
 198
 199         drm_bridge_remove(&vga->bridge);
 200
 201         if (!IS_ERR(vga->ddc))
 202                 i2c_put_adapter(vga->ddc);
 203
 204         return 0;
 205 }
 206
 207 static const struct of_device_id dumb_vga_match[] = {
 208         { .compatible = "dumb-vga-dac" },
 209         {},
 210 };
 211 MODULE_DEVICE_TABLE(of, dumb_vga_match);
 212
 213 static struct platform_driver dumb_vga_driver = {
 214         .probe  = dumb_vga_probe,
 215         .remove = dumb_vga_remove,
 216         .driver         = {
 217                 .name           = "dumb-vga-dac",
 218                 .of_match_table = dumb_vga_match,
 219         },
 220 };
 221 module_platform_driver(dumb_vga_driver);
 222
 223 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 224 MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
 225 MODULE_LICENSE("GPL");