# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2 --- $id: http://devicetree.org/schemas/display/panel/panel-edp.yaml# $schema: http://devicetree.org/meta-schemas/core.yaml# title: Probeable (via DP AUX / EDID) eDP Panels with simple poweron sequences maintainers: - Douglas Anderson description: | This binding file can be used to indicate that an eDP panel is connected to a Embedded DisplayPort AUX bus (see display/dp-aux-bus.yaml) without actually specifying exactly what panel is connected. This is useful for the case that more than one different panel could be connected to the board, either for second-sourcing purposes or to support multiple SKUs with different LCDs that hook up to a common board. As per above, a requirement for using this binding is that the panel is represented under the DP AUX bus. This means that we can use any information provided by the DP AUX bus (including the EDID) to identify the panel. We can use this to identify display size, resolution, and timings among other things. One piece of information about eDP panels that is typically _not_ provided anywhere on the DP AUX bus is the power sequencing timings. This is the reason why, historically, we've always had to explicitly list eDP panels. We solve that here with two tricks. The "worst case" power on timings for any panels expected to be connected to a board are specified in these bindings. Once we've powered on, it's expected that the operating system will lookup the panel in a table (based on EDID information) to figure out other power sequencing timings. eDP panels in general can have somewhat arbitrary power sequencing requirements. However, even though it's arbitrary in general, the vast majority of panel datasheets have a power sequence diagram that looks the exactly the same as every other panel. Each panel datasheet cares about different timings in this diagram but the fact that the diagram is so similar means we can come up with a single driver to handle it. These diagrams all look roughly like this, sometimes labeled with slightly different numbers / lines but all pretty much the same sequence. This is because much of this diagram comes straight from the eDP Standard. __________________________________________________ Vdd ___/: :\____ / _/ : : \_____/ ::: :<--T10-->::: : +-----------------------+---------+---------+ eDP -----------+ Black video | Src vid | Blk vid + Display : +-----------------------+---------+---------+ : _______________________:_________:_________: HPD :| : : | ___________| : : |_____________ : : : : Sink +-----------------------:---------:---------+ AUX CH -----------+ AUX Ch operational : : +------------- +-----------------------:---------:---------+ : : : : :: :: : : Src main +------+------+--------------+---------+ lnk data----------------+LnkTrn| Idle |Valid vid data| Idle/off+------------- +------+------+--------------+---------+ : :<-T6->:<-T8->: : :__:: LED_EN | | _____________________________________| |____________________________ : : __________:__:_ PWM | : : | __________________________| : : |__________________________ : : : : _____________:__________:__:_:______ Bklight ____/: : : : : :\____ power _______/ :<---T13---->: : : :: \______________ (Vbl) ::<---------T14--------->: :<-T15->:: The above looks fairly complex but, as per above, each panel only cares about a subset of those timings. allOf: - $ref: panel-common.yaml# properties: compatible: const: edp-panel hpd-reliable-delay-ms: description: A fixed amount of time that must be waited after powering on the panel's power-supply before the HPD signal is a reliable way to know when the AUX channel is ready. This is useful for panels that glitch the HPD at the start of power-on. This value is not needed if HPD is always reliable for all panels that might be connected. hpd-absent-delay-ms: description: The panel specifies that HPD will be asserted this many milliseconds from power on (timing T3 in the diagram above). If we have no way to measure HPD then a fixed delay of this many milliseconds can be used. This can also be used as a timeout when waiting for HPD. Does not include the hpd-reliable-delay, so if hpd-reliable-delay was 80 ms and hpd-absent-delay was 200 ms then we'd do a fixed 80 ms delay and then we know HPD would assert in the next 120 ms. This value is not needed if HPD hooked up, either through a GPIO in the panel node or hooked up directly to the eDP controller. backlight: true enable-gpios: true port: true power-supply: true no-hpd: true hpd-gpios: true additionalProperties: false required: - compatible - power-supply examples: - | #include #include #include i2c { #address-cells = <1>; #size-cells = <0>; bridge@2d { compatible = "ti,sn65dsi86"; reg = <0x2d>; interrupt-parent = <&tlmm>; interrupts = <10 IRQ_TYPE_LEVEL_HIGH>; enable-gpios = <&tlmm 102 GPIO_ACTIVE_HIGH>; vpll-supply = <&src_pp1800_s4a>; vccio-supply = <&src_pp1800_s4a>; vcca-supply = <&src_pp1200_l2a>; vcc-supply = <&src_pp1200_l2a>; clocks = <&rpmhcc RPMH_LN_BB_CLK2>; clock-names = "refclk"; no-hpd; ports { #address-cells = <1>; #size-cells = <0>; port@0 { reg = <0>; endpoint { remote-endpoint = <&dsi0_out>; }; }; port@1 { reg = <1>; sn65dsi86_out: endpoint { remote-endpoint = <&panel_in_edp>; }; }; }; aux-bus { panel { compatible = "edp-panel"; power-supply = <&pp3300_dx_edp>; backlight = <&backlight>; hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>; hpd-reliable-delay-ms = <15>; port { panel_in_edp: endpoint { remote-endpoint = <&sn65dsi86_out>; }; }; }; }; }; };