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         return drm_add_edid_modes(connector, edid);
  57
  58 fallback:
  59         /*
  60          * In case we cannot retrieve the EDIDs (broken or missing i2c
  61          * bus), fallback on the XGA standards
  62          */
  63         ret = drm_add_modes_noedid(connector, 1920, 1200);
  64
  65         /* And prefer a mode pretty much anyone can handle */
  66         drm_set_preferred_mode(connector, 1024, 768);
  67
  68         return ret;
  69 }
  70
  71 static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
  72         .get_modes      = dumb_vga_get_modes,
  73 };
  74
  75 static enum drm_connector_status
  76 dumb_vga_connector_detect(struct drm_connector *connector, bool force)
  77 {
  78         struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
  79
  80         /*
  81          * Even if we have an I2C bus, we can't assume that the cable
  82          * is disconnected if drm_probe_ddc fails. Some cables don't
  83          * wire the DDC pins, or the I2C bus might not be working at
  84          * all.
  85          */
  86         if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
  87                 return connector_status_connected;
  88
  89         return connector_status_unknown;
  90 }
  91
  92 static const struct drm_connector_funcs dumb_vga_con_funcs = {
  93         .dpms                   = drm_atomic_helper_connector_dpms,
  94         .detect                 = dumb_vga_connector_detect,
  95         .fill_modes             = drm_helper_probe_single_connector_modes,
  96         .destroy                = drm_connector_cleanup,
  97         .reset                  = drm_atomic_helper_connector_reset,
  98         .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
  99         .atomic_destroy_state   = drm_atomic_helper_connector_destroy_state,
 100 };
 101
 102 static int dumb_vga_attach(struct drm_bridge *bridge)
 103 {
 104         struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
 105         int ret;
 106
 107         if (!bridge->encoder) {
 108                 DRM_ERROR("Missing encoder\n");
 109                 return -ENODEV;
 110         }
 111
 112         drm_connector_helper_add(&vga->connector,
 113                                  &dumb_vga_con_helper_funcs);
 114         ret = drm_connector_init(bridge->dev, &vga->connector,
 115                                  &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA);
 116         if (ret) {
 117                 DRM_ERROR("Failed to initialize connector\n");
 118                 return ret;
 119         }
 120
 121         drm_mode_connector_attach_encoder(&vga->connector,
 122                                           bridge->encoder);
 123
 124         return 0;
 125 }
 126
 127 static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
 128         .attach         = dumb_vga_attach,
 129 };
 130
 131 static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
 132 {
 133         struct device_node *end_node, *phandle, *remote;
 134         struct i2c_adapter *ddc;
 135
 136         end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
 137         if (!end_node) {
 138                 dev_err(dev, "Missing connector endpoint\n");
 139                 return ERR_PTR(-ENODEV);
 140         }
 141
 142         remote = of_graph_get_remote_port_parent(end_node);
 143         of_node_put(end_node);
 144         if (!remote) {
 145                 dev_err(dev, "Enable to parse remote node\n");
 146                 return ERR_PTR(-EINVAL);
 147         }
 148
 149         phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
 150         of_node_put(remote);
 151         if (!phandle)
 152                 return ERR_PTR(-ENODEV);
 153
 154         ddc = of_get_i2c_adapter_by_node(phandle);
 155         of_node_put(phandle);
 156         if (!ddc)
 157                 return ERR_PTR(-EPROBE_DEFER);
 158
 159         return ddc;
 160 }
 161
 162 static int dumb_vga_probe(struct platform_device *pdev)
 163 {
 164         struct dumb_vga *vga;
 165         int ret;
 166
 167         vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
 168         if (!vga)
 169                 return -ENOMEM;
 170         platform_set_drvdata(pdev, vga);
 171
 172         vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
 173         if (IS_ERR(vga->ddc)) {
 174                 if (PTR_ERR(vga->ddc) == -ENODEV) {
 175                         dev_dbg(&pdev->dev,
 176                                 "No i2c bus specified. Disabling EDID readout\n");
 177                 } else {
 178                         dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
 179                         return PTR_ERR(vga->ddc);
 180                 }
 181         }
 182
 183         vga->bridge.funcs = &dumb_vga_bridge_funcs;
 184         vga->bridge.of_node = pdev->dev.of_node;
 185
 186         ret = drm_bridge_add(&vga->bridge);
 187         if (ret && !IS_ERR(vga->ddc))
 188                 i2c_put_adapter(vga->ddc);
 189
 190         return ret;
 191 }
 192
 193 static int dumb_vga_remove(struct platform_device *pdev)
 194 {
 195         struct dumb_vga *vga = platform_get_drvdata(pdev);
 196
 197         drm_bridge_remove(&vga->bridge);
 198
 199         if (!IS_ERR(vga->ddc))
 200                 i2c_put_adapter(vga->ddc);
 201
 202         return 0;
 203 }
 204
 205 static const struct of_device_id dumb_vga_match[] = {
 206         { .compatible = "dumb-vga-dac" },
 207         {},
 208 };
 209 MODULE_DEVICE_TABLE(of, dumb_vga_match);
 210
 211 static struct platform_driver dumb_vga_driver = {
 212         .probe  = dumb_vga_probe,
 213         .remove = dumb_vga_remove,
 214         .driver         = {
 215                 .name           = "dumb-vga-dac",
 216                 .of_match_table = dumb_vga_match,
 217         },
 218 };
 219 module_platform_driver(dumb_vga_driver);
 220
 221 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 222 MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
 223 MODULE_LICENSE("GPL");