target/linux/bcm27xx/patches-5.10/950-0507-overlays-gpio-led-new-overlay.patch

   1 From 095bad7f310809a951735d03be9d06938524a6bc Mon Sep 17 00:00:00 2001
   2 From: Assaf Gordon <assafgordon@gmail.com>
   3 Date: Fri, 12 Mar 2021 00:13:07 -0700
   4 Subject: [PATCH] overlays: gpio-led: new overlay
   5
   6 Add generic connection between the kernel's LED framework and
   7 RPI's GPIO pins.
   8
   9 Signed-off-by: Assaf Gordon <assafgordon@gmail.com>
  10 ---
  11  arch/arm/boot/dts/overlays/Makefile           |  1 +
  12  arch/arm/boot/dts/overlays/README             | 56 +++++++++++
  13  .../boot/dts/overlays/gpio-led-overlay.dts    | 97 +++++++++++++++++++
  14  3 files changed, 154 insertions(+)
  15  create mode 100755 arch/arm/boot/dts/overlays/gpio-led-overlay.dts
  16
  17 --- a/arch/arm/boot/dts/overlays/Makefile
  18 +++ b/arch/arm/boot/dts/overlays/Makefile
  19 @@ -54,6 +54,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
  20         gpio-ir.dtbo \
  21         gpio-ir-tx.dtbo \
  22         gpio-key.dtbo \
  23 +       gpio-led.dtbo \
  24         gpio-no-bank0-irq.dtbo \
  25         gpio-no-irq.dtbo \
  26         gpio-poweroff.dtbo \
  27 --- a/arch/arm/boot/dts/overlays/README
  28 +++ b/arch/arm/boot/dts/overlays/README
  29 @@ -914,6 +914,62 @@ Params: gpio                    GPIO pin
  30          keycode                 Set the key code for the button
  31
  32
  33 +
  34 +Name:   gpio-led
  35 +Info:   This is a generic overlay for activating LEDs (or any other component)
  36 +        by a GPIO pin. Multiple LEDs can be set up using multiple calls to the
  37 +        overlay. While there are many existing methods to activate LEDs on the
  38 +        RPi, this method offers some advantages:
  39 +        1) Does not require any userspace programs.
  40 +        2) LEDs can be connected to the kernel's led-trigger framework,
  41 +           and drive the LED based on triggers such as cpu load, heartbeat,
  42 +           kernel panic, key input, timers and others.
  43 +        3) LED can be tied to the input state of another GPIO pin.
  44 +        4) The LED is setup early during the kernel boot process (useful
  45 +           for cpu/heartbeat/panic triggers).
  46 +
  47 +        Typical electrical connection is:
  48 +           RPI-GPIO.19  ->  LED  -> 300ohm resister  -> RPI-GND
  49 +        The GPIO pin number can be changed with the 'gpio=' parameter.
  50 +
  51 +        To control an LED from userspace, write a 0 or 1 value:
  52 +           echo 1 > /sys/class/leds/myled1/brightness
  53 +        The 'myled1' name can be changed with the 'label=' parameter.
  54 +
  55 +        To connect the LED to a kernel trigger from userspace:
  56 +           echo cpu > /sys/class/leds/myled1/trigger
  57 +           echo heartbeat > /sys/class/leds/myled1/trigger
  58 +           echo none > /sys/class/leds/myled1/trigger
  59 +        To connect the LED to GPIO.26 pin (physical pin 37):
  60 +           echo gpio > /sys/class/leds/myled1/trigger
  61 +           echo 26 > /sys/class/leds/myled1/gpio
  62 +        Available triggers:
  63 +           cat /sys/class/leds/myled1/trigger
  64 +
  65 +        More information about the Linux kernel LED/Trigger system:
  66 +           https://www.kernel.org/doc/Documentation/leds/leds-class.rst
  67 +           https://www.kernel.org/doc/Documentation/leds/ledtrig-oneshot.rst
  68 +Load:   dtoverlay=gpio-led,<param>=<val>
  69 +Params: gpio                    GPIO pin connected to the LED (default 19)
  70 +        label                   The label for this LED. It will appear under
  71 +                                /sys/class/leds/<label> . Default 'myled1'.
  72 +        trigger                 Set the led-trigger to connect to this LED.
  73 +                                default 'none' (LED is user-controlled).
  74 +                                Some possible triggers:
  75 +                                 cpu - CPU load (all CPUs)
  76 +                                 cpu0 - CPU load of first CPU.
  77 +                                 mmc - disk activity (all disks)
  78 +                                 panic - turn on on kernel panic
  79 +                                 heartbeat - indicate system health
  80 +                                 gpio - connect to a GPIO input pin (note:
  81 +                                        currently the GPIO PIN can not be set
  82 +                                        using overlay parameters, must be
  83 +                                        done in userspace, see examples above.
  84 +        active_low              Set to 1 to turn invert the LED control
  85 +                                (writing 0 to /sys/class/leds/XXX/brightness
  86 +                                will turn on the GPIO/LED). Default '0'.
  87 +
  88 +
  89  Name:   gpio-no-bank0-irq
  90  Info:   Use this overlay to disable GPIO interrupts for GPIOs in bank 0 (0-27),
  91          which can be useful for UIO drivers.
  92 --- /dev/null
  93 +++ b/arch/arm/boot/dts/overlays/gpio-led-overlay.dts
  94 @@ -0,0 +1,97 @@
  95 +// SPDX-License-Identifier: GPL-2.0-or-later
  96 +/*
  97 + * gpio-led - generic connection of kernel's LED framework to the RPI's GPIO.
  98 + * Copyright (C) 2021 House Gordon Software Company Ltd. <assafgordon@gmail.com>
  99 + *
 100 + * Based on information from:
 101 + *   https://mjoldfield.com/atelier/2017/03/rpi-devicetree.html
 102 + *   https://www.raspberrypi.org/documentation/configuration/device-tree.md
 103 + *   https://www.kernel.org/doc/html/latest/leds/index.html
 104 + *
 105 + * compile with:
 106 + *   dtc -@ -Hepapr -I dts -O dtb -o gpio-led.dtbo gpio-led-overlay.dts
 107 + *
 108 + * There will be some warnings (can be ignored):
 109 + *  Warning (label_is_string): /__overrides__:label: property is not a string
 110 + *  Warning (unit_address_vs_reg): /fragment@0/__overlay__/led_pins@0:
 111 + *                                 node has a unit name, but no reg property
 112 + *  Warning (unit_address_vs_reg): /fragment@1/__overlay__/leds@0:
 113 + *                                 node has a unit name, but no reg property
 114 + *  Warning (gpios_property): /__overrides__: Missing property
 115 + *                 '#gpio-cells' in node /fragment@1/__overlay__/leds@0/led
 116 + *                  or bad phandle (referred from gpio[0])
 117 + *
 118 + * Typical electrical connection is:
 119 + *    RPI-GPIO.19  ->  LED  -> 300ohm resister  -> RPI-GND
 120 + *    The GPIO pin number can be changed with the 'gpio=' parameter.
 121 + *
 122 + * Test from user-space with:
 123 + *   # if nothing is shown, the overlay file isn't found in /boot/overlays
 124 + *   dtoverlay -a | grep gpio-led
 125 + *
 126 + *   # Load the overlay
 127 + *   dtoverlay gpio-led label=moo gpio=19
 128 + *
 129 + *   # if nothing is shown, the overlay wasn't loaded successfully
 130 + *   dtoverlay -l | grep gpio-led
 131 + *
 132 + *   echo 1 > /sys/class/leds/moo/brightness
 133 + *   echo 0 > /sys/class/leds/moo/brightness
 134 + *   echo cpu > /sys/class/leds/moo/trigger
 135 + *   echo heartbeat > /sys/class/leds/moo/trigger
 136 + *
 137 + *   # unload the overlay
 138 + *   dtoverlay -r gpio-led
 139 + *
 140 + * To load in /boot/config.txt add lines such as:
 141 + *   dtoverlay=gpio-led,gpio=19,label=heart,trigger=heartbeat
 142 + *   dtoverlay=gpio-led,gpio=26,label=brain,trigger=cpu
 143 + */
 144 +
 145 +/dts-v1/;
 146 +/plugin/;
 147 +
 148 +/ {
 149 +       compatible = "brcm,bcm2835";
 150 +
 151 +       fragment@0 {
 152 +               // Configure the gpio pin controller
 153 +               target = <&gpio>;
 154 +               __overlay__ {
 155 +                       led_pin: led_pins@19 {
 156 +                               brcm,pins = <19>; // gpio number
 157 +                               brcm,function = <1>; // 0 = input, 1 = output
 158 +                               brcm,pull = <0>; // 0 = none, 1 = pull down, 2 = pull up
 159 +                       };
 160 +               };
 161 +       };
 162 +       fragment@1 {
 163 +               target-path = "/";
 164 +               __overlay__ {
 165 +                       leds: leds@0 {
 166 +                               compatible = "gpio-leds";
 167 +                               pinctrl-names = "default";
 168 +                               pinctrl-0 = <&led_pin>;
 169 +                               status = "okay";
 170 +
 171 +                               led: led {
 172 +                                       label = "myled1";
 173 +                                       gpios = <&gpio 19 0>;
 174 +                                       linux,default-trigger = "none";
 175 +                               };
 176 +                       };
 177 +               };
 178 +       };
 179 +
 180 +       __overrides__ {
 181 +               gpio =       <&led>,"gpios:4",
 182 +                            <&leds>,"reg:0",
 183 +                            <&led_pin>,"brcm,pins:0",
 184 +                            <&led_pin>,"reg:0";
 185 +               label =      <&led>,"label";
 186 +               active_low = <&led>,"gpios:8";
 187 +               trigger =    <&led>,"linux,default-trigger";
 188 +       };
 189 +
 190 +};
 191 +