1 # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 %YAML 1.2
3 ---
4 $id: http://devicetree.org/schemas/display/panel/panel-edp.yaml#
5 $schema: http://devicetree.org/meta-schemas/core.yaml#
6
7 title: Probeable (via DP AUX / EDID) eDP Panels with simple poweron sequences
8
9 maintainers:
10 - Douglas Anderson <dianders@chromium.org>
11
12 description: |
13 This binding file can be used to indicate that an eDP panel is connected
14 to a Embedded DisplayPort AUX bus (see display/dp-aux-bus.yaml) without
15 actually specifying exactly what panel is connected. This is useful for
16 the case that more than one different panel could be connected to the
17 board, either for second-sourcing purposes or to support multiple SKUs
18 with different LCDs that hook up to a common board.
19
20 As per above, a requirement for using this binding is that the panel is
21 represented under the DP AUX bus. This means that we can use any
22 information provided by the DP AUX bus (including the EDID) to identify
23 the panel. We can use this to identify display size, resolution, and
24 timings among other things.
25
26 One piece of information about eDP panels that is typically _not_
27 provided anywhere on the DP AUX bus is the power sequencing timings.
28 This is the reason why, historically, we've always had to explicitly
29 list eDP panels. We solve that here with two tricks. The "worst case"
30 power on timings for any panels expected to be connected to a board are
31 specified in these bindings. Once we've powered on, it's expected that
32 the operating system will lookup the panel in a table (based on EDID
33 information) to figure out other power sequencing timings.
34
35 eDP panels in general can have somewhat arbitrary power sequencing
36 requirements. However, even though it's arbitrary in general, the
37 vast majority of panel datasheets have a power sequence diagram that
38 looks the exactly the same as every other panel. Each panel datasheet
39 cares about different timings in this diagram but the fact that the
40 diagram is so similar means we can come up with a single driver to
41 handle it.
42
43 These diagrams all look roughly like this, sometimes labeled with
44 slightly different numbers / lines but all pretty much the same
45 sequence. This is because much of this diagram comes straight from
46 the eDP Standard.
47
48 __________________________________________________
49 Vdd ___/: :\____ /
50 _/ : : \_____/
51 :<T1>:<T2>: :<--T10-->:<T11>:<T12>:
52 : +-----------------------+---------+---------+
53 eDP -----------+ Black video | Src vid | Blk vid +
54 Display : +-----------------------+---------+---------+
55 : _______________________:_________:_________:
56 HPD :<T3>| : : |
57 ___________| : : |_____________
58 : : : :
59 Sink +-----------------------:---------:---------+
60 AUX CH -----------+ AUX Ch operational : : +-------------
61 +-----------------------:---------:---------+
62 : : : :
63 :<T4>: :<T7>: : :
64 Src main +------+------+--------------+---------+
65 lnk data----------------+LnkTrn| Idle |Valid vid data| Idle/off+-------------
66 +------+------+--------------+---------+
67 : <T5> :<-T6->:<-T8->: :
68 :__:<T9>:
69 LED_EN | |
70 _____________________________________| |____________________________
71 : :
72 __________:__:_
73 PWM | : : |
74 __________________________| : : |__________________________
75 : : : :
76 _____________:__________:__:_:______
77 Bklight ____/: : : : : :\____
78 power _______/ :<---T13---->: : : :<T16>: \______________
79 (Vbl) :<T17>:<---------T14--------->: :<-T15->:<T18>:
80
81 The above looks fairly complex but, as per above, each panel only cares
82 about a subset of those timings.
83
84 allOf:
85 - $ref: panel-common.yaml#
86
87 properties:
88 compatible:
89 const: edp-panel
90
91 hpd-reliable-delay-ms:
92 description:
93 A fixed amount of time that must be waited after powering on the
94 panel's power-supply before the HPD signal is a reliable way to know
95 when the AUX channel is ready. This is useful for panels that glitch
96 the HPD at the start of power-on. This value is not needed if HPD is
97 always reliable for all panels that might be connected.
98
99 hpd-absent-delay-ms:
100 description:
101 The panel specifies that HPD will be asserted this many milliseconds
102 from power on (timing T3 in the diagram above). If we have no way to
103 measure HPD then a fixed delay of this many milliseconds can be used.
104 This can also be used as a timeout when waiting for HPD. Does not
105 include the hpd-reliable-delay, so if hpd-reliable-delay was 80 ms
106 and hpd-absent-delay was 200 ms then we'd do a fixed 80 ms delay and
107 then we know HPD would assert in the next 120 ms. This value is not
108 needed if HPD hooked up, either through a GPIO in the panel node or
109 hooked up directly to the eDP controller.
110
111 backlight: true
112 enable-gpios: true
113 port: true
114 power-supply: true
115 no-hpd: true
116 hpd-gpios: true
117
118 additionalProperties: false
119
120 required:
121 - compatible
122 - power-supply
123
124 examples:
125 - |
126 #include <dt-bindings/clock/qcom,rpmh.h>
127 #include <dt-bindings/gpio/gpio.h>
128 #include <dt-bindings/interrupt-controller/irq.h>
129
130 i2c {
131 #address-cells = <1>;
132 #size-cells = <0>;
133
134 bridge@2d {
135 compatible = "ti,sn65dsi86";
136 reg = <0x2d>;
137
138 interrupt-parent = <&tlmm>;
139 interrupts = <10 IRQ_TYPE_LEVEL_HIGH>;
140
141 enable-gpios = <&tlmm 102 GPIO_ACTIVE_HIGH>;
142
143 vpll-supply = <&src_pp1800_s4a>;
144 vccio-supply = <&src_pp1800_s4a>;
145 vcca-supply = <&src_pp1200_l2a>;
146 vcc-supply = <&src_pp1200_l2a>;
147
148 clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
149 clock-names = "refclk";
150
151 no-hpd;
152
153 ports {
154 #address-cells = <1>;
155 #size-cells = <0>;
156
157 port@0 {
158 reg = <0>;
159 endpoint {
160 remote-endpoint = <&dsi0_out>;
161 };
162 };
163
164 port@1 {
165 reg = <1>;
166 sn65dsi86_out: endpoint {
167 remote-endpoint = <&panel_in_edp>;
168 };
169 };
170 };
171
172 aux-bus {
173 panel {
174 compatible = "edp-panel";
175 power-supply = <&pp3300_dx_edp>;
176 backlight = <&backlight>;
177 hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
178 hpd-reliable-delay-ms = <15>;
179
180 port {
181 panel_in_edp: endpoint {
182 remote-endpoint = <&sn65dsi86_out>;
183 };
184 };
185 };
186 };
187 };
188 };
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