Bindings/display/panel/panel-edp.yaml

   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     };