189 lines
7.3 KiB
YAML
189 lines
7.3 KiB
YAML
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# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/display/panel/panel-edp.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: Probeable (via DP AUX / EDID) eDP Panels with simple poweron sequences
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maintainers:
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- Douglas Anderson <dianders@chromium.org>
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description: |
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This binding file can be used to indicate that an eDP panel is connected
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to a Embedded DisplayPort AUX bus (see display/dp-aux-bus.yaml) without
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actually specifying exactly what panel is connected. This is useful for
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the case that more than one different panel could be connected to the
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board, either for second-sourcing purposes or to support multiple SKUs
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with different LCDs that hook up to a common board.
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As per above, a requirement for using this binding is that the panel is
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represented under the DP AUX bus. This means that we can use any
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information provided by the DP AUX bus (including the EDID) to identify
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the panel. We can use this to identify display size, resolution, and
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timings among other things.
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One piece of information about eDP panels that is typically _not_
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provided anywhere on the DP AUX bus is the power sequencing timings.
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This is the reason why, historically, we've always had to explicitly
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list eDP panels. We solve that here with two tricks. The "worst case"
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power on timings for any panels expected to be connected to a board are
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specified in these bindings. Once we've powered on, it's expected that
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the operating system will lookup the panel in a table (based on EDID
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information) to figure out other power sequencing timings.
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eDP panels in general can have somewhat arbitrary power sequencing
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requirements. However, even though it's arbitrary in general, the
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vast majority of panel datasheets have a power sequence diagram that
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looks the exactly the same as every other panel. Each panel datasheet
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cares about different timings in this diagram but the fact that the
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diagram is so similar means we can come up with a single driver to
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handle it.
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These diagrams all look roughly like this, sometimes labeled with
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slightly different numbers / lines but all pretty much the same
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sequence. This is because much of this diagram comes straight from
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the eDP Standard.
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__________________________________________________
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Vdd ___/: :\____ /
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_/ : : \_____/
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:<T1>:<T2>: :<--T10-->:<T11>:<T12>:
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: +-----------------------+---------+---------+
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eDP -----------+ Black video | Src vid | Blk vid +
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Display : +-----------------------+---------+---------+
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: _______________________:_________:_________:
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HPD :<T3>| : : |
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___________| : : |_____________
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: : : :
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Sink +-----------------------:---------:---------+
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AUX CH -----------+ AUX Ch operational : : +-------------
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+-----------------------:---------:---------+
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: : : :
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:<T4>: :<T7>: : :
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Src main +------+------+--------------+---------+
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lnk data----------------+LnkTrn| Idle |Valid vid data| Idle/off+-------------
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+------+------+--------------+---------+
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: <T5> :<-T6->:<-T8->: :
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:__:<T9>:
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LED_EN | |
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_____________________________________| |____________________________
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: :
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__________:__:_
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PWM | : : |
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__________________________| : : |__________________________
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: : : :
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_____________:__________:__:_:______
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Bklight ____/: : : : : :\____
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power _______/ :<---T13---->: : : :<T16>: \______________
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(Vbl) :<T17>:<---------T14--------->: :<-T15->:<T18>:
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The above looks fairly complex but, as per above, each panel only cares
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about a subset of those timings.
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allOf:
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- $ref: panel-common.yaml#
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properties:
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compatible:
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const: edp-panel
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hpd-reliable-delay-ms:
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description:
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A fixed amount of time that must be waited after powering on the
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panel's power-supply before the HPD signal is a reliable way to know
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when the AUX channel is ready. This is useful for panels that glitch
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the HPD at the start of power-on. This value is not needed if HPD is
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always reliable for all panels that might be connected.
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hpd-absent-delay-ms:
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description:
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The panel specifies that HPD will be asserted this many milliseconds
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from power on (timing T3 in the diagram above). If we have no way to
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measure HPD then a fixed delay of this many milliseconds can be used.
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This can also be used as a timeout when waiting for HPD. Does not
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include the hpd-reliable-delay, so if hpd-reliable-delay was 80 ms
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and hpd-absent-delay was 200 ms then we'd do a fixed 80 ms delay and
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then we know HPD would assert in the next 120 ms. This value is not
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needed if HPD hooked up, either through a GPIO in the panel node or
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hooked up directly to the eDP controller.
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backlight: true
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enable-gpios: true
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port: true
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power-supply: true
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no-hpd: true
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hpd-gpios: true
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additionalProperties: false
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required:
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- compatible
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- power-supply
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examples:
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- |
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#include <dt-bindings/clock/qcom,rpmh.h>
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#include <dt-bindings/gpio/gpio.h>
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#include <dt-bindings/interrupt-controller/irq.h>
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i2c {
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#address-cells = <1>;
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#size-cells = <0>;
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bridge@2d {
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compatible = "ti,sn65dsi86";
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reg = <0x2d>;
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interrupt-parent = <&tlmm>;
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interrupts = <10 IRQ_TYPE_LEVEL_HIGH>;
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enable-gpios = <&tlmm 102 GPIO_ACTIVE_HIGH>;
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vpll-supply = <&src_pp1800_s4a>;
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vccio-supply = <&src_pp1800_s4a>;
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vcca-supply = <&src_pp1200_l2a>;
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vcc-supply = <&src_pp1200_l2a>;
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clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
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clock-names = "refclk";
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no-hpd;
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ports {
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#address-cells = <1>;
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#size-cells = <0>;
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port@0 {
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reg = <0>;
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endpoint {
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remote-endpoint = <&dsi0_out>;
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};
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};
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port@1 {
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reg = <1>;
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sn65dsi86_out: endpoint {
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remote-endpoint = <&panel_in_edp>;
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};
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};
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};
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aux-bus {
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panel {
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compatible = "edp-panel";
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power-supply = <&pp3300_dx_edp>;
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backlight = <&backlight>;
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hpd-gpios = <&sn65dsi86_bridge 2 GPIO_ACTIVE_HIGH>;
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hpd-reliable-delay-ms = <15>;
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port {
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panel_in_edp: endpoint {
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remote-endpoint = <&sn65dsi86_out>;
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};
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};
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};
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};
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};
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};
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