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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 (!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 (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_with_ddc(bridge->dev, &vga->connector,
115 &dumb_vga_con_funcs,
116 DRM_MODE_CONNECTOR_VGA,
117 vga->ddc);
118 if (ret) {
119 DRM_ERROR("Failed to initialize connector\n");
120 return ret;
121 }
122
123 drm_connector_attach_encoder(&vga->connector,
124 bridge->encoder);
125
126 return 0;
127}
128
129static void dumb_vga_enable(struct drm_bridge *bridge)
130{
131 struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
132 int ret = 0;
133
134 if (vga->vdd)
135 ret = regulator_enable(vga->vdd);
136
137 if (ret)
138 DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
139}
140
141static void dumb_vga_disable(struct drm_bridge *bridge)
142{
143 struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
144
145 if (vga->vdd)
146 regulator_disable(vga->vdd);
147}
148
149static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
150 .attach = dumb_vga_attach,
151 .enable = dumb_vga_enable,
152 .disable = dumb_vga_disable,
153};
154
155static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
156{
157 struct device_node *phandle, *remote;
158 struct i2c_adapter *ddc;
159
160 remote = of_graph_get_remote_node(dev->of_node, 1, -1);
161 if (!remote)
162 return ERR_PTR(-EINVAL);
163
164 phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
165 of_node_put(remote);
166 if (!phandle)
167 return ERR_PTR(-ENODEV);
168
169 ddc = of_get_i2c_adapter_by_node(phandle);
170 of_node_put(phandle);
171 if (!ddc)
172 return ERR_PTR(-EPROBE_DEFER);
173
174 return ddc;
175}
176
177static int dumb_vga_probe(struct platform_device *pdev)
178{
179 struct dumb_vga *vga;
180
181 vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
182 if (!vga)
183 return -ENOMEM;
184 platform_set_drvdata(pdev, vga);
185
186 vga->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
187 if (IS_ERR(vga->vdd)) {
188 int ret = PTR_ERR(vga->vdd);
189 if (ret == -EPROBE_DEFER)
190 return -EPROBE_DEFER;
191 vga->vdd = NULL;
192 dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
193 }
194
195 vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
196 if (IS_ERR(vga->ddc)) {
197 if (PTR_ERR(vga->ddc) == -ENODEV) {
198 dev_dbg(&pdev->dev,
199 "No i2c bus specified. Disabling EDID readout\n");
200 vga->ddc = NULL;
201 } else {
202 dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
203 return PTR_ERR(vga->ddc);
204 }
205 }
206
207 vga->bridge.funcs = &dumb_vga_bridge_funcs;
208 vga->bridge.of_node = pdev->dev.of_node;
209 vga->bridge.timings = of_device_get_match_data(&pdev->dev);
210
211 drm_bridge_add(&vga->bridge);
212
213 return 0;
214}
215
216static int dumb_vga_remove(struct platform_device *pdev)
217{
218 struct dumb_vga *vga = platform_get_drvdata(pdev);
219
220 drm_bridge_remove(&vga->bridge);
221
222 if (vga->ddc)
223 i2c_put_adapter(vga->ddc);
224
225 return 0;
226}
227
228/*
229 * We assume the ADV7123 DAC is the "default" for historical reasons
230 * Information taken from the ADV7123 datasheet, revision D.
231 * NOTE: the ADV7123EP seems to have other timings and need a new timings
232 * set if used.
233 */
234static const struct drm_bridge_timings default_dac_timings = {
235 /* Timing specifications, datasheet page 7 */
236 .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
237 .setup_time_ps = 500,
238 .hold_time_ps = 1500,
239};
240
241/*
242 * Information taken from the THS8134, THS8134A, THS8134B datasheet named
243 * "SLVS205D", dated May 1990, revised March 2000.
244 */
245static const struct drm_bridge_timings ti_ths8134_dac_timings = {
246 /* From timing diagram, datasheet page 9 */
247 .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
248 /* From datasheet, page 12 */
249 .setup_time_ps = 3000,
250 /* I guess this means latched input */
251 .hold_time_ps = 0,
252};
253
254/*
255 * Information taken from the THS8135 datasheet named "SLAS343B", dated
256 * May 2001, revised April 2013.
257 */
258static const struct drm_bridge_timings ti_ths8135_dac_timings = {
259 /* From timing diagram, datasheet page 14 */
260 .input_bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
261 /* From datasheet, page 16 */
262 .setup_time_ps = 2000,
263 .hold_time_ps = 500,
264};
265
266static const struct of_device_id dumb_vga_match[] = {
267 {
268 .compatible = "dumb-vga-dac",
269 .data = NULL,
270 },
271 {
272 .compatible = "adi,adv7123",
273 .data = &default_dac_timings,
274 },
275 {
276 .compatible = "ti,ths8135",
277 .data = &ti_ths8135_dac_timings,
278 },
279 {
280 .compatible = "ti,ths8134",
281 .data = &ti_ths8134_dac_timings,
282 },
283 {},
284};
285MODULE_DEVICE_TABLE(of, dumb_vga_match);
286
287static struct platform_driver dumb_vga_driver = {
288 .probe = dumb_vga_probe,
289 .remove = dumb_vga_remove,
290 .driver = {
291 .name = "dumb-vga-dac",
292 .of_match_table = dumb_vga_match,
293 },
294};
295module_platform_driver(dumb_vga_driver);
296
297MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
298MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
299MODULE_LICENSE("GPL");