linux核心驅動 TI OMAP類處理器的LED所涉及到裝置樹彙整
阿新 • • 發佈：2019-01-16
樣例擷取自linux4.1.13中，與裝置樹有關BeagleBone Black 的部分程式碼,
1、 定位GPIO控制器在處理的外圍地址：
GPIO0 記憶體對映：
GPIO1 記憶體對映：
GPIO2、GPIO3 記憶體對映：
2、CONTROL_MODULE控制模式的暫存器位置：
3、引腳複用地址：
4、 Linux裝置樹對上述GPIO對映的實現如下：
/ {
compatible = "ti,am33xx";
interrupt-parent = <&intc>;
ocp {
compatible = "simple-bus";
#address-cells = <1>;
#size-cells = <1>;
ranges;
ti,hwmods = "l3_main";
gpio0: 5、控制模式器和引腳複用記憶體對映
ocp {
compatible = "simple-bus";
#address-cells = <1>;
#size-cells = <1>;
ranges;
ti,hwmods = "l3_main";
l4_wkup: [email protected] {
compatible = "ti,am3-l4-wkup", "simple-bus";
#address-cells = <1>;
#size-cells = <1>;
ranges = <0 0x44c00000 0x280000>;
scm: [email protected] {
compatible = "ti,am3-scm", "simple-bus";
reg = <0x210000 0x2000>;
#address-cells = <1>;
#size-cells = <1>;
ranges = <0 0x210000 0x2000>;
/*
*計算下 控制模式的地址 = 0x44c00000+0x210000=0x44E1000
*引腳複用地址=0x44E1000+0x800 = 0x44E10800
*/
am33xx_pinmux: [email protected] {
compatible = "pinctrl-single";
reg = <0x800 0x238>;
#address-cells = <1>;
#size-cells = <0>;
pinctrl-single,register-width = <32>;
pinctrl-single,function-mask = <0x7f>;
};
};
};
6、開啟處理器的內部引腳複用、上下拉等屬性有關的CONTROL_MODULE：
TI的處理器有專門的控制器模式，用於設定IO屬性。處理器的部分引腳有複用功能，必須記得設定引腳複用單元，此處開啟的是beaglebone black上的4個usr led，其詳細的引腳位置不貼出了，請查閱相關手冊。
&am33xx_pinmux {
pinctrl-names = "default";
pinctrl-0 = <&clkout2_pin>;
user_leds_s0: user_leds_s0 {
pinctrl-single,pins = <
0x54 (PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* gpmc_a5.gpio1_21 */
0x58 (PIN_OUTPUT_PULLUP | MUX_MODE7) /* gpmc_a6.gpio1_22 */
0x5c (PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* gpmc_a7.gpio1_23 */
0x60 (PIN_OUTPUT_PULLUP | MUX_MODE7) /* gpmc_a8.gpio1_24 */
>;
}
}7、linux核心與驅動LED有關的裝置樹實現：
/{
leds {
pinctrl-names = "default";
pinctrl-0 = <&user_leds_s0>;
compatible = "gpio-leds";
[email protected] {
label = "beaglebone:green:heartbeat";
gpios = <&gpio1 21 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "heartbeat";
default-state = "off";
};
[email protected] {
label = "beaglebone:green:mmc0";
gpios = <&gpio1 22 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "mmc0";
default-state = "off";
};
[email protected] {
label = "beaglebone:green:usr2";
gpios = <&gpio1 23 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "cpu0";
default-state = "off";
};
[email protected] {
label = "beaglebone:green:usr3";
gpios = <&gpio1 24 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "mmc1";
default-state = "off";
};
}8、 TI處理器有關的linux核心對有關的gpio、pinctrl-single、gpio-leds的裝置樹屬性定義的描述：
8.1 ti， omap2-gpio 屬性描述，摘自核心的目錄下的/Documentation/devicetree/bindings/gpio/gpio-omap.txt
OMAP GPIO controller bindings
Required properties:
- compatible:
- "ti,omap2-gpio" for OMAP2 controllers
- "ti,omap3-gpio" for OMAP3 controllers
- "ti,omap4-gpio" for OMAP4 controllers
- gpio-controller : Marks the device node as a GPIO controller.
- #gpio-cells : Should be two.
- first cell is the pin number
- second cell is used to specify optional parameters (unused)
- interrupt-controller: Mark the device node as an interrupt controller.
- #interrupt-cells : Should be 2.
The first cell is the GPIO number.
The second cell is used to specify flags:
bits[3:0] trigger type and level flags:
1 = low-to-high edge triggered.
2 = high-to-low edge triggered.
4 = active high level-sensitive.
8 = active low level-sensitive.
OMAP specific properties:
- ti,hwmods: Name of the hwmod associated to the GPIO:
"gpio<X>", <X> being the 1-based instance number
from the HW spec.
- ti,gpio-always-on: Indicates if a GPIO bank is always powered and
so will never lose its logic state.
Example:
gpio4: gpio4 {
compatible = "ti,omap4-gpio";
ti,hwmods = "gpio4";
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
};
8.2 pinctrl-single，摘自核心的目錄下的/Documentation/devicetree/bindings/pinctrl/pinctrl-single.txt
One-register-per-pin type device tree based pinctrl driver
Required properties:
- compatible : "pinctrl-single" or "pinconf-single".
"pinctrl-single" means that pinconf isn't supported.
"pinconf-single" means that generic pinconf is supported.
- reg : offset and length of the register set for the mux registers
- pinctrl-single,register-width : pinmux register access width in bits
- pinctrl-single,function-mask : mask of allowed pinmux function bits
in the pinmux register
Optional properties:
- pinctrl-single,function-off : function off mode for disabled state if
available and same for all registers; if not specified, disabling of
pin functions is ignored
- pinctrl-single,bit-per-mux : boolean to indicate that one register controls
more than one pin, for which "pinctrl-single,function-mask" property specifies
position mask of pin.
- pinctrl-single,drive-strength : array of value that are used to configure
drive strength in the pinmux register. They're value of drive strength
current and drive strength mask.
/* drive strength current, mask */
pinctrl-single,power-source = <0x30 0xf0>;
- pinctrl-single,bias-pullup : array of value that are used to configure the
input bias pullup in the pinmux register.
/* input, enabled pullup bits, disabled pullup bits, mask */
pinctrl-single,bias-pullup = <0 1 0 1>;
- pinctrl-single,bias-pulldown : array of value that are used to configure the
input bias pulldown in the pinmux register.
/* input, enabled pulldown bits, disabled pulldown bits, mask */
pinctrl-single,bias-pulldown = <2 2 0 2>;
* Two bits to control input bias pullup and pulldown: User should use
pinctrl-single,bias-pullup & pinctrl-single,bias-pulldown. One bit means
pullup, and the other one bit means pulldown.
* Three bits to control input bias enable, pullup and pulldown. User should
use pinctrl-single,bias-pullup & pinctrl-single,bias-pulldown. Input bias
enable bit should be included in pullup or pulldown bits.
* Although driver could set PIN_CONFIG_BIAS_DISABLE, there's no property as
pinctrl-single,bias-disable. Because pinctrl single driver could implement
it by calling pulldown, pullup disabled.
- pinctrl-single,input-schmitt : array of value that are used to configure
input schmitt in the pinmux register. In some silicons, there're two input
schmitt value (rising-edge & falling-edge) in the pinmux register.
/* input schmitt value, mask */
pinctrl-single,input-schmitt = <0x30 0x70>;
- pinctrl-single,input-schmitt-enable : array of value that are used to
configure input schmitt enable or disable in the pinmux register.
/* input, enable bits, disable bits, mask */
pinctrl-single,input-schmitt-enable = <0x30 0x40 0 0x70>;
- pinctrl-single,low-power-mode : array of value that are used to configure
low power mode of this pin. For some silicons, the low power mode will
control the output of the pin when the pad including the pin enter low
power mode.
/* low power mode value, mask */
pinctrl-single,low-power-mode = <0x288 0x388>;
- pinctrl-single,gpio-range : list of value that are used to configure a GPIO
range. They're value of subnode phandle, pin base in pinctrl device, pin
number in this range, GPIO function value of this GPIO range.
The number of parameters is depend on #pinctrl-single,gpio-range-cells
property.
/* pin base, nr pins & gpio function */
pinctrl-single,gpio-range = <&range 0 3 0 &range 3 9 1>;
- interrupt-controller : standard interrupt controller binding if using
interrupts for wake-up events for example. In this case pinctrl-single
is set up as a chained interrupt controller and the wake-up interrupts
can be requested by the drivers using request_irq().
- #interrupt-cells : standard interrupt binding if using interrupts
This driver assumes that there is only one register for each pin (unless the
pinctrl-single,bit-per-mux is set), and uses the common pinctrl bindings as
specified in the pinctrl-bindings.txt document in this directory.
The pin configuration nodes for pinctrl-single are specified as pinctrl
register offset and value pairs using pinctrl-single,pins. Only the bits
specified in pinctrl-single,function-mask are updated. For example, setting
a pin for a device could be done with:
pinctrl-single,pins = <0xdc 0x118>;
Where 0xdc is the offset from the pinctrl register base address for the
device pinctrl register, and 0x118 contains the desired value of the
pinctrl register. See the device example and static board pins example
below for more information.
In case when one register changes more than one pin's mux the
pinctrl-single,bits need to be used which takes three parameters:
pinctrl-single,bits = <0xdc 0x18 0xff>;
Where 0xdc is the offset from the pinctrl register base address for the
device pinctrl register, 0x18 is the desired value, and 0xff is the sub mask to
be used when applying this change to the register.
Optional sub-node: In case some pins could be configured as GPIO in the pinmux
register, those pins could be defined as a GPIO range. This sub-node is required
by pinctrl-single,gpio-range property.
Required properties in sub-node:
- #pinctrl-single,gpio-range-cells : the number of parameters after phandle in
pinctrl-single,gpio-range property.
range: gpio-range {
#pinctrl-single,gpio-range-cells = <3>;
};
Example:
/* SoC common file */
/* first controller instance for pins in core domain */
pmx_core: [email protected] {
compatible = "pinctrl-single";
reg = <0x4a100040 0x0196>;
#address-cells = <1>;
#size-cells = <0>;
#interrupt-cells = <1>;
interrupt-controller;
pinctrl-single,register-width = <16>;
pinctrl-single,function-mask = <0xffff>;
};
/* second controller instance for pins in wkup domain */
pmx_wkup: [email protected] {
compatible = "pinctrl-single";
reg = <0x4a31e040 0x0038>;
#address-cells = <1>;
#size-cells = <0>;
#interrupt-cells = <1>;
interrupt-controller;
pinctrl-single,register-width = <16>;
pinctrl-single,function-mask = <0xffff>;
};
control_devconf0: [email protected] {
compatible = "pinctrl-single";
reg = <0x48002274 4>; /* Single register */
#address-cells = <1>;
#size-cells = <0>;
pinctrl-single,bit-per-mux;
pinctrl-single,register-width = <32>;
pinctrl-single,function-mask = <0x5F>;
};
/* third controller instance for pins in gpio domain */
pmx_gpio: [email protected] {
compatible = "pinconf-single";
reg = <0xd401e000 0x0330>;
#address-cells = <1>;
#size-cells = <1>;
ranges;
pinctrl-single,register-width = <32>;
pinctrl-single,function-mask = <7>;
/* sparse GPIO range could be supported */
pinctrl-single,gpio-range = <&range 0 3 0 &range 3 9 1
&range 12 1 0 &range 13 29 1
&range 43 1 0 &range 44 49 1
&range 94 1 1 &range 96 2 1>;
range: gpio-range {
#pinctrl-single,gpio-range-cells = <3>;
};
};
/* board specific .dts file */
&pmx_core {
/*
* map all board specific static pins enabled by the pinctrl driver
* itself during the boot (or just set them up in the bootloader)
*/
pinctrl-names = "default";
pinctrl-0 = <&board_pins>;
board_pins: pinmux_board_pins {
pinctrl-single,pins = <
0x6c 0xf
0x6e 0xf
0x70 0xf
0x72 0xf
>;
};
uart0_pins: pinmux_uart0_pins {
pinctrl-single,pins = <
0x208 0 /* UART0_RXD (IOCFG138) */
0x20c 0 /* UART0_TXD (IOCFG139) */
>;
pinctrl-single,bias-pulldown = <0 2 2>;
pinctrl-single,bias-pullup = <0 1 1>;
};
/* map uart2 pins */
uart2_pins: pinmux_uart2_pins {
pinctrl-single,pins = <
0xd8 0x118
0xda 0
0xdc 0x118
0xde 0
>;
};
};
&control_devconf0 {
mcbsp1_pins: pinmux_mcbsp1_pins {
pinctrl-single,bits = <
0x00 0x18 0x18 /* FSR/CLKR signal from FSX/CLKX pin */
>;
};
mcbsp2_clks_pins: pinmux_mcbsp2_clks_pins {
pinctrl-single,bits = <
0x00 0x40 0x40 /* McBSP2 CLKS from McBSP_CLKS pin */
>;
};
};
&uart1 {
pinctrl-names = "default";
pinctrl-0 = <&uart0_pins>;
};
&uart2 {
pinctrl-names = "default";
pinctrl-0 = <&uart2_pins>;
};8.3 gpio-leds，摘自核心的目錄下的/Documentation/devicetree/bindings/leds/txtleds-gpio.txt
LEDs connected to GPIO lines
Required properties:
- compatible : should be "gpio-leds".
Each LED is represented as a sub-node of the gpio-leds device. Each
node's name represents the name of the corresponding LED.
LED sub-node properties:
- gpios : Should specify the LED's GPIO, see "gpios property" in
Documentation/devicetree/bindings/gpio/gpio.txt. Active low LEDs should be
indicated using flags in the GPIO specifier.
- label : (optional)
see Documentation/devicetree/bindings/leds/common.txt
- linux,default-trigger : (optional)
see Documentation/devicetree/bindings/leds/common.txt
- default-state: (optional) The initial state of the LED. Valid
values are "on", "off", and "keep". If the LED is already on or off
and the default-state property is set the to same value, then no
glitch should be produced where the LED momentarily turns off (or
on). The "keep" setting will keep the LED at whatever its current
state is, without producing a glitch. The default is off if this
property is not present.
- retain-state-suspended: (optional) The suspend state can be retained.Such
as charge-led gpio.
Examples:
#include <dt-bindings/gpio/gpio.h>
leds {
compatible = "gpio-leds";
hdd {
label = "IDE Activity";
gpios = <&mcu_pio 0 GPIO_ACTIVE_LOW>;
linux,default-trigger = "ide-disk";
};
fault {
gpios = <&mcu_pio 1 GPIO_ACTIVE_HIGH>;
/* Keep LED on if BIOS detected hardware fault */
default-state = "keep";
};
};
run-control {
compatible = "gpio-leds";
red {
gpios = <&mpc8572 6 GPIO_ACTIVE_HIGH>;
default-state = "off";
};
green {
gpios = <&mpc8572 7 GPIO_ACTIVE_HIGH>;
default-state = "on";
};
};
leds {
compatible = "gpio-leds";
charger-led {
gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "max8903-charger-charging";
retain-state-suspended;
};
};Documentation/devicetree/bindings/leds/common.txt
Common leds properties.
LED and flash LED devices provide the same basic functionality as current
regulators, but extended with LED and flash LED specific features like
blinking patterns, flash timeout, flash faults and external flash strobe mode.
Many LED devices expose more than one current output that can be connected
to one or more discrete LED component. Since the arrangement of connections
can influence the way of the LED device initialization, the LED components
have to be tightly coupled with the LED device binding. They are represented
by child nodes of the parent LED device binding.
Optional properties for child nodes:
- led-sources : List of device current outputs the LED is connected to. The
outputs are identified by the numbers that must be defined
in the LED device binding documentation.
- label : The label for this LED. If omitted, the label is taken from the node
name (excluding the unit address). It has to uniquely identify
a device, i.e. no other LED class device can be assigned the same
label.
- linux,default-trigger : This parameter, if present, is a
string defining the trigger assigned to the LED. Current triggers are:
"backlight" - LED will act as a back-light, controlled by the framebuffer
system
"default-on" - LED will turn on (but for leds-gpio see "default-state"
property in Documentation/devicetree/bindings/gpio/led.txt)
"heartbeat" - LED "double" flashes at a load average based rate
"ide-disk" - LED indicates disk activity
"timer" - LED flashes at a fixed, configurable rate
- max-microamp : maximum intensity in microamperes of the LED
(torch LED for flash devices)
- flash-max-microamp : maximum intensity in microamperes of the
flash LED; it is mandatory if the LED should
support the flash mode
- flash-timeout-us : timeout in microseconds after which the flash
LED is turned off
Examples:
system-status {
label = "Status";
linux,default-trigger = "heartbeat";
...
};
camera-flash {
label = "Flash";
led-sources = <0>, <1>;
max-microamp = <50000>;
flash-max-microamp = <320000>;
flash-timeout-us = <500000>;
};9.總結：
開發一個led的驅動，實質涉及就兩大塊：其一就是硬體底層有關的實現，其二就是呼叫硬體底層來實現使用者功能（低階使用者功能）。
本例在硬體底層中，涉及的主要是gpio控制、控制模式的引腳複用，而要使她們能正常工作，又需要載入相應的驅動模組，而裝置樹的“compatible”為其找尋相應的驅動提供了路徑，
led使用者層的功能的驅動就要勞駕“gpio-leds” --compatible 屬性來實現。
參考：
1、AM335x ARM ® CortexTM-A8 Microprocessors (MPUs) Technical Reference Manual
2、 linux4.1.13
備註：
1。 20160206, wiwa 完成初稿
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/**************************************************************************/ /***************************led.c********************************************