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

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2016 Free Electrons
   4  * Copyright (C) 2015-2016 NextThing Co
   5  *
   6  * Maxime Ripard <maxime.ripard@free-electrons.com>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/of_device.h>
  11 #include <linux/of_graph.h>
  12 #include <linux/regulator/consumer.h>
  13
  14 #include <drm/drm_atomic_helper.h>
  15 #include <drm/drm_crtc.h>
  16 #include <drm/drm_print.h>
  17 #include <drm/drm_probe_helper.h>
  18
  19 struct dumb_vga {
  20         struct drm_bridge       bridge;
  21         struct drm_connector    connector;
  22
  23         struct i2c_adapter      *ddc;
  24         struct regulator        *vdd;
  25 };
  26
  27 static inline struct dumb_vga *
  28 drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
  29 {
  30         return container_of(bridge, struct dumb_vga, bridge);
  31 }
  32
  33 static inline struct dumb_vga *
  34 drm_connector_to_dumb_vga(struct drm_connector *connector)
  35 {
  36         return container_of(connector, struct dumb_vga, connector);
  37 }
  38
  39 static int dumb_vga_get_modes(struct drm_connector *connector)
  40 {
  41         struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
  42         struct edid *edid;
  43         int ret;
  44
  45         if (IS_ERR(vga->ddc))
  46                 goto fallback;
  47
  48         edid = drm_get_edid(connector, vga->ddc);
  49         if (!edid) {
  50                 DRM_INFO("EDID readout failed, falling back to standard modes\n");
  51                 goto fallback;
  52         }
  53
  54         drm_connector_update_edid_property(connector, edid);
  55         ret = drm_add_edid_modes(connector, edid);
  56         kfree(edid);
  57         return ret;
  58
  59 fallback:
  60         /*
  61          * In case we cannot retrieve the EDIDs (broken or missing i2c
  62          * bus), fallback on the XGA standards
  63          */
  64         ret = drm_add_modes_noedid(connector, 1920, 1200);
  65
  66         /* And prefer a mode pretty much anyone can handle */
  67         drm_set_preferred_mode(connector, 1024, 768);
  68
  69         return ret;
  70 }
  71
  72 static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
  73         .get_modes      = dumb_vga_get_modes,
  74 };
  75
  76 static enum drm_connector_status
  77 dumb_vga_connector_detect(struct drm_connector *connector, bool force)
  78 {
  79         struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
  80
  81         /*
  82          * Even if we have an I2C bus, we can't assume that the cable
  83          * is disconnected if drm_probe_ddc fails. Some cables don't
  84          * wire the DDC pins, or the I2C bus might not be working at
  85          * all.
  86          */
  87         if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
  88                 return connector_status_connected;
  89
  90         return connector_status_unknown;
  91 }
  92
  93 static const struct drm_connector_funcs dumb_vga_con_funcs = {
  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_connector_attach_encoder(&vga->connector,
 122                                           bridge->encoder);
 123
 124         return 0;
 125 }
 126
 127 static void dumb_vga_enable(struct drm_bridge *bridge)
 128 {
 129         struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
 130         int ret = 0;
 131
 132         if (vga->vdd)
 133                 ret = regulator_enable(vga->vdd);
 134
 135         if (ret)
 136                 DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
 137 }
 138
 139 static void dumb_vga_disable(struct drm_bridge *bridge)
 140 {
 141         struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
 142
 143         if (vga->vdd)
 144                 regulator_disable(vga->vdd);
 145 }
 146
 147 static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
 148         .attach         = dumb_vga_attach,
 149         .enable         = dumb_vga_enable,
 150         .disable        = dumb_vga_disable,
 151 };
 152
 153 static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
 154 {
 155         struct device_node *phandle, *remote;
 156         struct i2c_adapter *ddc;
 157
 158         remote = of_graph_get_remote_node(dev->of_node, 1, -1);
 159         if (!remote)
 160                 return ERR_PTR(-EINVAL);
 161
 162         phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
 163         of_node_put(remote);
 164         if (!phandle)
 165                 return ERR_PTR(-ENODEV);
 166
 167         ddc = of_get_i2c_adapter_by_node(phandle);
 168         of_node_put(phandle);
 169         if (!ddc)
 170                 return ERR_PTR(-EPROBE_DEFER);
 171
 172         return ddc;
 173 }
 174
 175 static int dumb_vga_probe(struct platform_device *pdev)
 176 {
 177         struct dumb_vga *vga;
 178
 179         vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
 180         if (!vga)
 181                 return -ENOMEM;
 182         platform_set_drvdata(pdev, vga);
 183
 184         vga->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
 185         if (IS_ERR(vga->vdd)) {
 186                 int ret = PTR_ERR(vga->vdd);
 187                 if (ret == -EPROBE_DEFER)
 188                         return -EPROBE_DEFER;
 189                 vga->vdd = NULL;
 190                 dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
 191         }
 192
 193         vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
 194         if (IS_ERR(vga->ddc)) {
 195                 if (PTR_ERR(vga->ddc) == -ENODEV) {
 196                         dev_dbg(&pdev->dev,
 197                                 "No i2c bus specified. Disabling EDID readout\n");
 198                 } else {
 199                         dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
 200                         return PTR_ERR(vga->ddc);
 201                 }
 202         }
 203
 204         vga->bridge.funcs = &dumb_vga_bridge_funcs;
 205         vga->bridge.of_node = pdev->dev.of_node;
 206         vga->bridge.timings = of_device_get_match_data(&pdev->dev);
 207
 208         drm_bridge_add(&vga->bridge);
 209
 210         return 0;
 211 }
 212
 213 static int dumb_vga_remove(struct platform_device *pdev)
 214 {
 215         struct dumb_vga *vga = platform_get_drvdata(pdev);
 216
 217         drm_bridge_remove(&vga->bridge);
 218
 219         if (!IS_ERR(vga->ddc))
 220                 i2c_put_adapter(vga->ddc);
 221
 222         return 0;
 223 }
 224
 225 /*
 226  * We assume the ADV7123 DAC is the "default" for historical reasons
 227  * Information taken from the ADV7123 datasheet, revision D.
 228  * NOTE: the ADV7123EP seems to have other timings and need a new timings
 229  * set if used.
 230  */
 231 static const struct drm_bridge_timings default_dac_timings = {
 232         /* Timing specifications, datasheet page 7 */
 233         .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
 234         .setup_time_ps = 500,
 235         .hold_time_ps = 1500,
 236 };
 237
 238 /*
 239  * Information taken from the THS8134, THS8134A, THS8134B datasheet named
 240  * "SLVS205D", dated May 1990, revised March 2000.
 241  */
 242 static const struct drm_bridge_timings ti_ths8134_dac_timings = {
 243         /* From timing diagram, datasheet page 9 */
 244         .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
 245         /* From datasheet, page 12 */
 246         .setup_time_ps = 3000,
 247         /* I guess this means latched input */
 248         .hold_time_ps = 0,
 249 };
 250
 251 /*
 252  * Information taken from the THS8135 datasheet named "SLAS343B", dated
 253  * May 2001, revised April 2013.
 254  */
 255 static const struct drm_bridge_timings ti_ths8135_dac_timings = {
 256         /* From timing diagram, datasheet page 14 */
 257         .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
 258         /* From datasheet, page 16 */
 259         .setup_time_ps = 2000,
 260         .hold_time_ps = 500,
 261 };
 262
 263 static const struct of_device_id dumb_vga_match[] = {
 264         {
 265                 .compatible = "dumb-vga-dac",
 266                 .data = NULL,
 267         },
 268         {
 269                 .compatible = "adi,adv7123",
 270                 .data = &default_dac_timings,
 271         },
 272         {
 273                 .compatible = "ti,ths8135",
 274                 .data = &ti_ths8135_dac_timings,
 275         },
 276         {
 277                 .compatible = "ti,ths8134",
 278                 .data = &ti_ths8134_dac_timings,
 279         },
 280         {},
 281 };
 282 MODULE_DEVICE_TABLE(of, dumb_vga_match);
 283
 284 static struct platform_driver dumb_vga_driver = {
 285         .probe  = dumb_vga_probe,
 286         .remove = dumb_vga_remove,
 287         .driver         = {
 288                 .name           = "dumb-vga-dac",
 289                 .of_match_table = dumb_vga_match,
 290         },
 291 };
 292 module_platform_driver(dumb_vga_driver);
 293
 294 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 295 MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
 296 MODULE_LICENSE("GPL");