LXR linux/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
  19struct dumb_vga {
  20        struct drm_bridge       bridge;
  21        struct drm_connector    connector;
  22
  23        struct i2c_adapter      *ddc;
  24        struct regulator        *vdd;
  25};
  26
  27static inline struct dumb_vga *
  28drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
  29{
  30        return container_of(bridge, struct dumb_vga, bridge);
  31}
  32
  33static inline struct dumb_vga *
  34drm_connector_to_dumb_vga(struct drm_connector *connector)
  35{
  36        return container_of(connector, struct dumb_vga, connector);
  37}
  38
  39static 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
  59fallback:
  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
  72static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
  73        .get_modes      = dumb_vga_get_modes,
  74};
  75
  76static enum drm_connector_status
  77dumb_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
  93static 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
 102static 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
 127static 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
 139static 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
 147static 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
 153static 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
 175static 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
 213static 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 */
 231static 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 */
 242static 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 */
 255static 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
 263static 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};
 282MODULE_DEVICE_TABLE(of, dumb_vga_match);
 283
 284static 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};
 292module_platform_driver(dumb_vga_driver);
 293
 294MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 295MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
 296MODULE_LICENSE("GPL");
 297