SN65DSI86: Screen become blank after sometime on sleep

Mani

How do you put the DSI86 into the sleep state? 

Does the issue show up with semi-auto link training?

For fast link training, SW needs to program both the DSI86 and the eDP panel with the calibrated settings, have you done that?

Thanks

David

Hi David,

Actually we are using semi auto link training and sorry for the confusion. If you look at the register dump the F8 reg is set to 0x06 when the issue happened. so it proves that the link training failure bit and semi auto link training bit are set. Why the link training suddenly failed and what causes that? We are only seeing 3 or 4 units with this failure and other units are working fine. Is this related to bad chip or SW?

Also when the issue happened we were tried writing 0x96 reg with 0x0a but after writing read back saying the value is 0x0.

Test starts
0 = 0x36
1 = 0x38
2 = 0x49
3 = 0x53
4 = 0x44
5 = 0x20
6 = 0x20
7 = 0x20
8 = 0x02
9 = 0x00
10 = 0x86
11 = 0x00
12 = 0x00
13 = 0x01
14 = 0x00
15 = 0x00
16 = 0x20
17 = 0x00
18 = 0x7b
19 = 0x00
20 = 0x00
21 = 0x00
22 = 0x00
23 = 0x00
24 = 0x00
25 = 0x00
26 = 0x00
27 = 0x00
28 = 0x00
29 = 0x00
30 = 0x00
31 = 0x00
32 = 0x70
33 = 0x08
34 = 0x00
35 = 0x00
36 = 0xa0
37 = 0x05
38 = 0x00
39 = 0x00
40 = 0x00
41 = 0x00
42 = 0x00
43 = 0x00
44 = 0x20
45 = 0x00
46 = 0x00
47 = 0x00
48 = 0x0a
49 = 0x00
50 = 0x00
51 = 0x00
52 = 0x50
53 = 0x00
54 = 0x1b
55 = 0x00
56 = 0x30
57 = 0x00
58 = 0x03
59 = 0x00
60 = 0x00
61 = 0x00
62 = 0x00
63 = 0x00
64 = 0xaf
65 = 0x61
66 = 0x00
67 = 0x00
68 = 0x80
69 = 0x00
70 = 0x10
71 = 0x09
72 = 0xc8
73 = 0x05
74 = 0x70
75 = 0x00
76 = 0x25
77 = 0x00
78 = 0x20
79 = 0x00
80 = 0x0a
81 = 0x00
82 = 0x70
83 = 0x08
84 = 0xa0
85 = 0x05
86 = 0x20
87 = 0x00
88 = 0x40
89 = 0xe4
90 = 0x0d
91 = 0x00
92 = 0x10
93 = 0x00
94 = 0xb0
95 = 0x00
96 = 0xa0
97 = 0x60
98 = 0xa4
99 = 0x00
100 = 0x00
101 = 0x00
102 = 0x00
103 = 0x00
104 = 0x00
105 = 0x00
106 = 0x00
107 = 0x00
108 = 0x00
109 = 0x00
110 = 0x00
111 = 0x00
112 = 0x00
113 = 0x00
114 = 0x00
115 = 0x00
116 = 0x00
117 = 0x01
118 = 0x02
119 = 0x01
120 = 0x80
121 = 0x00
122 = 0x00
123 = 0x00
124 = 0x00
125 = 0x00
126 = 0x00
127 = 0x00
128 = 0x00
129 = 0x00
130 = 0x00
131 = 0x00
132 = 0x00
133 = 0x00
134 = 0x00
135 = 0x00
136 = 0x00
137 = 0x1f
138 = 0x7c
139 = 0xf0
140 = 0xc1
141 = 0x07
142 = 0x1f
143 = 0x7c
144 = 0xf0
145 = 0xc1
146 = 0x07
147 = 0x30
148 = 0x80
149 = 0x00
150 = 0x00
151 = 0x04
152 = 0x01
153 = 0x00
154 = 0x00
155 = 0x00
156 = 0x00
157 = 0x00
158 = 0x00
159 = 0x00
160 = 0x01
161 = 0xff
162 = 0xff
163 = 0x00
164 = 0x00
165 = 0x00
166 = 0x00
167 = 0x00
168 = 0x00
169 = 0x00
170 = 0x00
171 = 0x00
172 = 0x00
173 = 0x00
174 = 0x00
175 = 0x00
176 = 0x04
177 = 0x78
178 = 0xac
179 = 0xac
180 = 0x08
181 = 0x6c
182 = 0x9c
183 = 0x9c
184 = 0x0c
185 = 0x5c
186 = 0x5c
187 = 0x5c
188 = 0x0c
189 = 0x0c
190 = 0x0c
191 = 0x0c
192 = 0x3f
193 = 0x3f
194 = 0x0f
195 = 0x00
196 = 0x00
197 = 0x00
198 = 0x00
199 = 0x00
200 = 0x00
201 = 0x00
202 = 0x00
203 = 0x00
204 = 0x00
205 = 0x00
206 = 0x00
207 = 0x00
208 = 0x00
209 = 0x00
210 = 0x00
211 = 0x00
212 = 0x00
213 = 0x00
214 = 0x00
215 = 0x00
216 = 0x00
217 = 0x00
218 = 0x00
219 = 0x00
220 = 0x00
221 = 0x00
222 = 0x00
223 = 0x00
224 = 0x00
225 = 0x00
226 = 0x00
227 = 0x00
228 = 0x00
229 = 0x00
230 = 0x00
231 = 0x00
232 = 0x00
233 = 0x00
234 = 0x00
235 = 0x00
236 = 0x00
237 = 0x00
238 = 0x00
239 = 0x00
240 = 0x00
241 = 0x00
242 = 0x00
243 = 0x00
244 = 0x01
245 = 0x02
246 = 0x00
247 = 0x00
248 = 0x06
249 = 0x00
250 = 0x00
251 = 0x00
252 = 0x00
253 = 0x00
254 = 0x00
255 = 0x00

Thanks

Mani

Mani

For the 3 or 4 units, do they work in normal mode and only have issue after waking up from the sleep state? If these units work in normal mode but only fail after waking up from the sleep state, then I don't think it is a unit issue, more a wake up timing issue. 

If training is unsuccessful, the SN65DSI86 will transition the ML_TX_MODE to Main Link Off. So if you start the semi-auto link training and training is unsuccessful, then I would expect the register 0x96 read back 0x00.

The register 0xF8 indicates link training failed because the clock recovery portion of the link training failed. Does the panel also go into sleep state when DSI86 goes into the sleep state? Do you wait until the panel comes out of the sleep state before start the semi-auto link training?

How does the DSI86 go into the sleep state?

Thanks

David

HI David,

This Link training failure is happening all the time. Right after the boot display backlight is ON  but nothing is on the screen (blank). It has nothing to do with sleep mode or wake up. sorry for the confusion in the tittle.

How to fix the clock recovery portion of the training?

Thanks

Mani

Mani

Can you do a unit swap and see if the issue follows the unit or the board? If the issue follows the unit, then I may need the unit back for further failure analysis.

For clock recovery failure, the DSI86 sends the TPS1 clock pattern at the Nyquist frequency of the data rate to the sink and the sink needs to lock to the TPS1 clock pattern. If it fails,

• Check the physical connection between the DSI86 and the sink
• Make sure the output lane order is correct
• Clock pattern amplitude may be too low
  • Use a shorter cable between the DSI86 and the sink
  • Change DSI86 VOD in the DP Link Training LUT registers

Thanks

David

Hi David,

The failure units are production product so physical connection and lane order are correct. The issue is not happening all the time so the physical connection should be good. We don't have shorter cable because the panel is connected through FPC to main board (fixed length). We can try changing the VOD in LUT but how to do that? Just random value or any specific value to reg 0xB0 thru 0xC3? 

We will try display swap test.

Thanks

Mani

Mani

I would focus on increasing the V(n)_P0_VOD. For clock signal, you shouldn't need pre-emphasis, only SWING.

Thanks

David

Hi David,

I have changed the TX swing but it didn't help for passing link training.

I am trying to write 0x96 reg with 0x0A value but the read back from the register showing 0x0 all the time but I can able to write 0x01 or 0x02  and also read back correctly. Why I am not able to write 0x0A on 0x96 reg?

How to clear the 0xF8 register since it is set to 0x06 after training failure? I know reboot will clear the registers but I want to clear it without reboot.

Planning for swap test today or tomorrow and update you the results.

Thanks

Mani

Mani

You can write 0xFF to register 0xF8 to clear it. 

You can write 0x96 to register 0x0A and that will start the link training. But if the link training failed, it will switch to MAIN_LINK_OFF.

Thanks

David

Hi David,

The swap test confirms that the issue is following the panel. So we requested our display vendor for FA.

I have one more unit which is not only failing in Link training there are other failures too like DSI error and Aux Error. Please look at the reg dump I have collected two times during the failure. Each time reg dump showing different values. I would like to get your feedback before doing swap test.

thanks

Mani

Hi David,

Aux Error:

1. Yes. The panel needs 100K pullup on AUXP/N

2. I will check the aux data

DSI Error:

1. After clearing the particular register DSI error is gone and it is not coming again.

Thanks

Mani

Mani

So the reported DSI error may not be real since you can clear it and it is not coming back. I would focus on the AUX error first.

Thanks
David