# 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 <dianders@chromium.org>
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 ___/: :\____ /
_/ : : \_____/
:<T1>:<T2>: :<--T10-->:<T11>:<T12>:
: +-----------------------+---------+---------+
eDP -----------+ Black video | Src vid | Blk vid +
Display : +-----------------------+---------+---------+
: _______________________:_________:_________:
HPD :<T3>| : : |
___________| : : |_____________
: : : :
Sink +-----------------------:---------:---------+
AUX CH -----------+ AUX Ch operational : : +-------------
+-----------------------:---------:---------+
: : : :
:<T4>: :<T7>: : :
Src main +------+------+--------------+---------+
lnk data----------------+LnkTrn| Idle |Valid vid data| Idle/off+-------------
+------+------+--------------+---------+
: <T5> :<-T6->:<-T8->: :
:__:<T9>:
LED_EN | |
_____________________________________| |____________________________
: :
__________:__:_
PWM | : : |
__________________________| : : |__________________________
: : : :
_____________:__________:__:_:______
Bklight ____/: : : : : :\____
power _______/ :<---T13---->: : : :<T16>: \______________
(Vbl) :<T17>:<---------T14--------->: :<-T15->:<T18>:
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 <dt-bindings/clock/qcom,rpmh.h>
#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/interrupt-controller/irq.h>
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>;
};
};
};
};
};
};