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_device.h>
 15#include <linux/of_graph.h>
 16#include <linux/regulator/consumer.h>
 17
 18#include <drm/drmP.h>
 19#include <drm/drm_atomic_helper.h>
 20#include <drm/drm_crtc.h>
 21#include <drm/drm_crtc_helper.h>
 22
 23struct dumb_vga {
 24	struct drm_bridge	bridge;
 25	struct drm_connector	connector;
 26
 27	struct i2c_adapter	*ddc;
 28	struct regulator	*vdd;
 29};
 30
 31static inline struct dumb_vga *
 32drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
 33{
 34	return container_of(bridge, struct dumb_vga, bridge);
 35}
 36
 37static inline struct dumb_vga *
 38drm_connector_to_dumb_vga(struct drm_connector *connector)
 39{
 40	return container_of(connector, struct dumb_vga, connector);
 41}
 42
 43static int dumb_vga_get_modes(struct drm_connector *connector)
 44{
 45	struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
 46	struct edid *edid;
 47	int ret;
 48
 49	if (IS_ERR(vga->ddc))
 50		goto fallback;
 51
 52	edid = drm_get_edid(connector, vga->ddc);
 53	if (!edid) {
 54		DRM_INFO("EDID readout failed, falling back to standard modes\n");
 55		goto fallback;
 56	}
 57
 58	drm_mode_connector_update_edid_property(connector, edid);
 59	ret = drm_add_edid_modes(connector, edid);
 60	kfree(edid);
 61	return ret;
 62
 63fallback:
 64	/*
 65	 * In case we cannot retrieve the EDIDs (broken or missing i2c
 66	 * bus), fallback on the XGA standards
 67	 */
 68	ret = drm_add_modes_noedid(connector, 1920, 1200);
 69
 70	/* And prefer a mode pretty much anyone can handle */
 71	drm_set_preferred_mode(connector, 1024, 768);
 72
 73	return ret;
 74}
 75
 76static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
 77	.get_modes	= dumb_vga_get_modes,
 78};
 79
 80static enum drm_connector_status
 81dumb_vga_connector_detect(struct drm_connector *connector, bool force)
 82{
 83	struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
 84
 85	/*
 86	 * Even if we have an I2C bus, we can't assume that the cable
 87	 * is disconnected if drm_probe_ddc fails. Some cables don't
 88	 * wire the DDC pins, or the I2C bus might not be working at
 89	 * all.
 90	 */
 91	if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
 92		return connector_status_connected;
 93
 94	return connector_status_unknown;
 95}
 96
 97static const struct drm_connector_funcs dumb_vga_con_funcs = {
 98	.detect			= dumb_vga_connector_detect,
 99	.fill_modes		= drm_helper_probe_single_connector_modes,
100	.destroy		= drm_connector_cleanup,
101	.reset			= drm_atomic_helper_connector_reset,
102	.atomic_duplicate_state	= drm_atomic_helper_connector_duplicate_state,
103	.atomic_destroy_state	= drm_atomic_helper_connector_destroy_state,
104};
105
106static int dumb_vga_attach(struct drm_bridge *bridge)
107{
108	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
109	int ret;
110
111	if (!bridge->encoder) {
112		DRM_ERROR("Missing encoder\n");
113		return -ENODEV;
114	}
115
116	drm_connector_helper_add(&vga->connector,
117				 &dumb_vga_con_helper_funcs);
118	ret = drm_connector_init(bridge->dev, &vga->connector,
119				 &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA);
120	if (ret) {
121		DRM_ERROR("Failed to initialize connector\n");
122		return ret;
123	}
124
125	drm_mode_connector_attach_encoder(&vga->connector,
126					  bridge->encoder);
127
128	return 0;
129}
130
131static void dumb_vga_enable(struct drm_bridge *bridge)
132{
133	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
134	int ret = 0;
135
136	if (vga->vdd)
137		ret = regulator_enable(vga->vdd);
138
139	if (ret)
140		DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
141}
142
143static void dumb_vga_disable(struct drm_bridge *bridge)
144{
145	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
146
147	if (vga->vdd)
148		regulator_disable(vga->vdd);
149}
150
151static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
152	.attach		= dumb_vga_attach,
153	.enable		= dumb_vga_enable,
154	.disable	= dumb_vga_disable,
155};
156
157static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
158{
159	struct device_node *phandle, *remote;
160	struct i2c_adapter *ddc;
161
162	remote = of_graph_get_remote_node(dev->of_node, 1, -1);
163	if (!remote)
164		return ERR_PTR(-EINVAL);
165
166	phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
167	of_node_put(remote);
168	if (!phandle)
169		return ERR_PTR(-ENODEV);
170
171	ddc = of_get_i2c_adapter_by_node(phandle);
172	of_node_put(phandle);
173	if (!ddc)
174		return ERR_PTR(-EPROBE_DEFER);
175
176	return ddc;
177}
178
179static int dumb_vga_probe(struct platform_device *pdev)
180{
181	struct dumb_vga *vga;
182
183	vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
184	if (!vga)
185		return -ENOMEM;
186	platform_set_drvdata(pdev, vga);
187
188	vga->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
189	if (IS_ERR(vga->vdd)) {
190		int ret = PTR_ERR(vga->vdd);
191		if (ret == -EPROBE_DEFER)
192			return -EPROBE_DEFER;
193		vga->vdd = NULL;
194		dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
195	}
196
197	vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
198	if (IS_ERR(vga->ddc)) {
199		if (PTR_ERR(vga->ddc) == -ENODEV) {
200			dev_dbg(&pdev->dev,
201				"No i2c bus specified. Disabling EDID readout\n");
202		} else {
203			dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
204			return PTR_ERR(vga->ddc);
205		}
206	}
207
208	vga->bridge.funcs = &dumb_vga_bridge_funcs;
209	vga->bridge.of_node = pdev->dev.of_node;
210	vga->bridge.timings = of_device_get_match_data(&pdev->dev);
211
212	drm_bridge_add(&vga->bridge);
213
214	return 0;
215}
216
217static int dumb_vga_remove(struct platform_device *pdev)
218{
219	struct dumb_vga *vga = platform_get_drvdata(pdev);
220
221	drm_bridge_remove(&vga->bridge);
222
223	if (!IS_ERR(vga->ddc))
224		i2c_put_adapter(vga->ddc);
225
226	return 0;
227}
228
229/*
230 * We assume the ADV7123 DAC is the "default" for historical reasons
231 * Information taken from the ADV7123 datasheet, revision D.
232 * NOTE: the ADV7123EP seems to have other timings and need a new timings
233 * set if used.
234 */
235static const struct drm_bridge_timings default_dac_timings = {
236	/* Timing specifications, datasheet page 7 */
237	.sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
238	.setup_time_ps = 500,
239	.hold_time_ps = 1500,
240};
241
242/*
243 * Information taken from the THS8134, THS8134A, THS8134B datasheet named
244 * "SLVS205D", dated May 1990, revised March 2000.
245 */
246static const struct drm_bridge_timings ti_ths8134_dac_timings = {
247	/* From timing diagram, datasheet page 9 */
248	.sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
249	/* From datasheet, page 12 */
250	.setup_time_ps = 3000,
251	/* I guess this means latched input */
252	.hold_time_ps = 0,
253};
254
255/*
256 * Information taken from the THS8135 datasheet named "SLAS343B", dated
257 * May 2001, revised April 2013.
258 */
259static const struct drm_bridge_timings ti_ths8135_dac_timings = {
260	/* From timing diagram, datasheet page 14 */
261	.sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
262	/* From datasheet, page 16 */
263	.setup_time_ps = 2000,
264	.hold_time_ps = 500,
265};
266
267static const struct of_device_id dumb_vga_match[] = {
268	{
269		.compatible = "dumb-vga-dac",
270		.data = NULL,
271	},
272	{
273		.compatible = "adi,adv7123",
274		.data = &default_dac_timings,
275	},
276	{
277		.compatible = "ti,ths8135",
278		.data = &ti_ths8135_dac_timings,
279	},
280	{
281		.compatible = "ti,ths8134",
282		.data = &ti_ths8134_dac_timings,
283	},
284	{},
285};
286MODULE_DEVICE_TABLE(of, dumb_vga_match);
287
288static struct platform_driver dumb_vga_driver = {
289	.probe	= dumb_vga_probe,
290	.remove	= dumb_vga_remove,
291	.driver		= {
292		.name		= "dumb-vga-dac",
293		.of_match_table	= dumb_vga_match,
294	},
295};
296module_platform_driver(dumb_vga_driver);
297
298MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
299MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
300MODULE_LICENSE("GPL");