1 /*
2 * Copyright (c) 2015 NVIDIA Corporation. All rights reserved.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sub license,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the
12 * next paragraph) shall be included in all copies or substantial portions
13 * of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24 #include <linux/slab.h>
25 #include <linux/delay.h>
26
27 #include <drm/drm_print.h>
28 #include <drm/drm_scdc_helper.h>
29
30 /**
31 * DOC: scdc helpers
32 *
33 * Status and Control Data Channel (SCDC) is a mechanism introduced by the
34 * HDMI 2.0 specification. It is a point-to-point protocol that allows the
35 * HDMI source and HDMI sink to exchange data. The same I2C interface that
36 * is used to access EDID serves as the transport mechanism for SCDC.
37 */
38
39 #define SCDC_I2C_SLAVE_ADDRESS 0x54
40
41 /**
42 * drm_scdc_read - read a block of data from SCDC
43 * @adapter: I2C controller
44 * @offset: start offset of block to read
45 * @buffer: return location for the block to read
46 * @size: size of the block to read
47 *
48 * Reads a block of data from SCDC, starting at a given offset.
49 *
50 * Returns:
51 * 0 on success, negative error code on failure.
52 */
53 ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer,
54 size_t size)
55 {
56 int ret;
57 struct i2c_msg msgs[2] = {
58 {
59 .addr = SCDC_I2C_SLAVE_ADDRESS,
60 .flags = 0,
61 .len = 1,
62 .buf = &offset,
63 }, {
64 .addr = SCDC_I2C_SLAVE_ADDRESS,
65 .flags = I2C_M_RD,
66 .len = size,
67 .buf = buffer,
68 }
69 };
70
71 ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
72 if (ret < 0)
73 return ret;
74 if (ret != ARRAY_SIZE(msgs))
75 return -EPROTO;
76
77 return 0;
78 }
79 EXPORT_SYMBOL(drm_scdc_read);
80
81 /**
82 * drm_scdc_write - write a block of data to SCDC
83 * @adapter: I2C controller
84 * @offset: start offset of block to write
85 * @buffer: block of data to write
86 * @size: size of the block to write
87 *
88 * Writes a block of data to SCDC, starting at a given offset.
89 *
90 * Returns:
91 * 0 on success, negative error code on failure.
92 */
93 ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
94 const void *buffer, size_t size)
95 {
96 struct i2c_msg msg = {
97 .addr = SCDC_I2C_SLAVE_ADDRESS,
98 .flags = 0,
99 .len = 1 + size,
100 .buf = NULL,
101 };
102 void *data;
103 int err;
104
105 data = kmalloc(1 + size, GFP_KERNEL);
106 if (!data)
107 return -ENOMEM;
108
109 msg.buf = data;
110
111 memcpy(data, &offset, sizeof(offset));
112 memcpy(data + 1, buffer, size);
113
114 err = i2c_transfer(adapter, &msg, 1);
115
116 kfree(data);
117
118 if (err < 0)
119 return err;
120 if (err != 1)
121 return -EPROTO;
122
123 return 0;
124 }
125 EXPORT_SYMBOL(drm_scdc_write);
126
127 /**
128 * drm_scdc_check_scrambling_status - what is status of scrambling?
129 * @adapter: I2C adapter for DDC channel
130 *
131 * Reads the scrambler status over SCDC, and checks the
132 * scrambling status.
133 *
134 * Returns:
135 * True if the scrambling is enabled, false otherwise.
136 */
137 bool drm_scdc_get_scrambling_status(struct i2c_adapter *adapter)
138 {
139 u8 status;
140 int ret;
141
142 ret = drm_scdc_readb(adapter, SCDC_SCRAMBLER_STATUS, &status);
143 if (ret < 0) {
144 DRM_DEBUG_KMS("Failed to read scrambling status: %d\n", ret);
145 return false;
146 }
147
148 return status & SCDC_SCRAMBLING_STATUS;
149 }
150 EXPORT_SYMBOL(drm_scdc_get_scrambling_status);
151
152 /**
153 * drm_scdc_set_scrambling - enable scrambling
154 * @adapter: I2C adapter for DDC channel
155 * @enable: bool to indicate if scrambling is to be enabled/disabled
156 *
157 * Writes the TMDS config register over SCDC channel, and:
158 * enables scrambling when enable = 1
159 * disables scrambling when enable = 0
160 *
161 * Returns:
162 * True if scrambling is set/reset successfully, false otherwise.
163 */
164 bool drm_scdc_set_scrambling(struct i2c_adapter *adapter, bool enable)
165 {
166 u8 config;
167 int ret;
168
169 ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
170 if (ret < 0) {
171 DRM_DEBUG_KMS("Failed to read TMDS config: %d\n", ret);
172 return false;
173 }
174
175 if (enable)
176 config |= SCDC_SCRAMBLING_ENABLE;
177 else
178 config &= ~SCDC_SCRAMBLING_ENABLE;
179
180 ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
181 if (ret < 0) {
182 DRM_DEBUG_KMS("Failed to enable scrambling: %d\n", ret);
183 return false;
184 }
185
186 return true;
187 }
188 EXPORT_SYMBOL(drm_scdc_set_scrambling);
189
190 /**
191 * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
192 * @adapter: I2C adapter for DDC channel
193 * @set: ret or reset the high clock ratio
194 *
195 *
196 * TMDS clock ratio calculations go like this:
197 * TMDS character = 10 bit TMDS encoded value
198 *
199 * TMDS character rate = The rate at which TMDS characters are
200 * transmitted (Mcsc)
201 *
202 * TMDS bit rate = 10x TMDS character rate
203 *
204 * As per the spec:
205 * TMDS clock rate for pixel clock < 340 MHz = 1x the character
206 * rate = 1/10 pixel clock rate
207 *
208 * TMDS clock rate for pixel clock > 340 MHz = 0.25x the character
209 * rate = 1/40 pixel clock rate
210 *
211 * Writes to the TMDS config register over SCDC channel, and:
212 * sets TMDS clock ratio to 1/40 when set = 1
213 *
214 * sets TMDS clock ratio to 1/10 when set = 0
215 *
216 * Returns:
217 * True if write is successful, false otherwise.
218 */
219 bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter, bool set)
220 {
221 u8 config;
222 int ret;
223
224 ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
225 if (ret < 0) {
226 DRM_DEBUG_KMS("Failed to read TMDS config: %d\n", ret);
227 return false;
228 }
229
230 if (set)
231 config |= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
232 else
233 config &= ~SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
234
235 ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
236 if (ret < 0) {
237 DRM_DEBUG_KMS("Failed to set TMDS clock ratio: %d\n", ret);
238 return false;
239 }
240
241 /*
242 * The spec says that a source should wait minimum 1ms and maximum
243 * 100ms after writing the TMDS config for clock ratio. Lets allow a
244 * wait of upto 2ms here.
245 */
246 usleep_range(1000, 2000);
247 return true;
248 }
249 EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);