本帖最后由 lonerzf 于 2014-3-20 14:36 编辑
最近正学习Device Tree，过了这么长一段时间，进展也不是很大。总结下，主要原因还是基础比较薄弱，不太明白DTS这个文件的写法，不清楚哪里去找一些常用的属性值。
补充几个缩写 （AM335x TRM Page 1972）
OMAP Open Multimedia Application Platform
PWMSS Pulse-Width Modulation Subsystem
ePWM enhanced PWM
eHRPWM enhanced high resolution PWM
eCAP enhanced Capture
eQEP enhanced Quadrature Encode Pulse
其中PWMSS 包括了 eHRPWM eCAP eQEP 几个功能模块。所以要使用ehrpwm1 那就必须先使能epwmss1。
好久之前发表过心得
BB Black 入门基础之 Device Tree 当时还不清楚具体怎么去写一个DTS文件，比如不知道target有哪些，就像下面这种。
fragment@0 {
- target = <&am33xx_pinmux>;
...
}
以及下面这种
- fragment@1 {
- target = <&epwmss1>;
- __overlay__ {
- status = "okay";
- };
- };
- fragment@2 {
- target = <&ehrpwm1>;
- __overlay__ {
- status = "okay";
- };
- };
看到了这里target = <&am33xx_pinmux>; 很多时候我们都不知道
am33xx_pinmux 这个东西它究竟是怎么来的。
这里大胆揣测一下，咱们平时常用的target就在下面包括了。
- am33xx_pinmux = "/pinmux@44e10800";
- user_leds_s0 = "/pinmux@44e10800/user_leds_s0";
- i2c0_pins = "/pinmux@44e10800/pinmux_i2c0_pins";
- uart0_pins = "/pinmux@44e10800/pinmux_uart0_pins";
- clkout2_pin = "/pinmux@44e10800/pinmux_clkout2_pin";
- cpsw_default = "/pinmux@44e10800/cpsw_default";
- cpsw_sleep = "/pinmux@44e10800/cpsw_sleep";
- davinci_mdio_default = "/pinmux@44e10800/davinci_mdio_default";
- davinci_mdio_sleep = "/pinmux@44e10800/davinci_mdio_sleep";
- i2c2_pins = "/pinmux@44e10800/pinmux_i2c2_pins";
- mmc1_pins = "/pinmux@44e10800/pinmux_mmc1_pins";
- nxp_hdmi_bonelt_pins = "/pinmux@44e10800/nxp_hdmi_bonelt_pins";
- intc = "/ocp/interrupt-controller@48200000";
- edma = "/ocp/edma@49000000";
- gpio0 = "/ocp/gpio@44e07000";
- gpio1 = "/ocp/gpio@4804c000";
- gpio2 = "/ocp/gpio@481ac000";
- gpio3 = "/ocp/gpio@481ae000";
- uart0 = "/ocp/serial@44e09000";
- uart1 = "/ocp/serial@48022000";
- uart2 = "/ocp/serial@48024000";
- uart3 = "/ocp/serial@481a6000";
- uart4 = "/ocp/serial@481a8000";
- uart5 = "/ocp/serial@481aa000";
- i2c0 = "/ocp/i2c@44e0b000";
- tps = "/ocp/i2c@44e0b000/tps@24";
- dcdc1_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@0";
- dcdc2_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@1";
- dcdc3_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@2";
- ldo1_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@3";
- ldo2_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@4";
- ldo3_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@5";
- ldo4_reg = "/ocp/i2c@44e0b000/tps@24/regulators/regulator@6";
- vmmcsd_fixed = "/ocp/i2c@44e0b000/tps@24/fixedregulator@0";
- baseboard_eeprom = "/ocp/i2c@44e0b000/baseboard_eeprom@50";
- i2c1 = "/ocp/i2c@4802a000";
- i2c2 = "/ocp/i2c@4819c000";
- cape_eeprom0 = "/ocp/i2c@4819c000/cape_eeprom0@54";
- cape_eeprom1 = "/ocp/i2c@4819c000/cape_eeprom1@55";
- cape_eeprom2 = "/ocp/i2c@4819c000/cape_eeprom2@56";
- cape_eeprom3 = "/ocp/i2c@4819c000/cape_eeprom3@57";
- mmc1 = "/ocp/mmc@48060000";
- mmc2 = "/ocp/mmc@481d8000";
- mmc3 = "/ocp/mmc@47810000";
- wdt2 = "/ocp/wdt@44e35000";
- dcan0 = "/ocp/d_can@481cc000";
- dcan1 = "/ocp/d_can@481d0000";
- timer1 = "/ocp/timer@44e31000";
- timer2 = "/ocp/timer@48040000";
- timer3 = "/ocp/timer@48042000";
- timer4 = "/ocp/timer@48044000";
- timer5 = "/ocp/timer@48046000";
- timer6 = "/ocp/timer@48048000";
- timer7 = "/ocp/timer@4804a000";
- spi0 = "/ocp/spi@48030000";
- spi1 = "/ocp/spi@481a0000";
- musb = "/ocp/usb@47400000";
- usb = "/ocp/usb@47400000";
- ctrl_mod = "/ocp/usb@47400000/control@44e10000";
- usb0_phy = "/ocp/usb@47400000/usb-phy@47401300";
- usb0 = "/ocp/usb@47400000/usb@47401000";
- usb1_phy = "/ocp/usb@47400000/usb-phy@47401b00";
- usb1 = "/ocp/usb@47400000/usb@47401800";
- cppi41dma = "/ocp/usb@47400000/dma-controller@07402000";
- epwmss0 = "/ocp/epwmss@48300000";
- ecap0 = "/ocp/epwmss@48300000/ecap@48300100";
- ehrpwm0 = "/ocp/epwmss@48300000/ehrpwm@48300200";
- epwmss1 = "/ocp/epwmss@48302000";
- ecap1 = "/ocp/epwmss@48302000/ecap@48302100";
- ehrpwm1 = "/ocp/epwmss@48302000/ehrpwm@48302200";
- epwmss2 = "/ocp/epwmss@48304000";
- ecap2 = "/ocp/epwmss@48304000/ecap@48304100";
- ehrpwm2 = "/ocp/epwmss@48304000/ehrpwm@48304200";
- mac = "/ocp/ethernet@4a100000";
- davinci_mdio = "/ocp/ethernet@4a100000/mdio@4a101000";
- cpsw_emac0 = "/ocp/ethernet@4a100000/slave@4a100200";
- cpsw_emac1 = "/ocp/ethernet@4a100000/slave@4a100300";
- ocmcram = "/ocp/ocmcram@40300000";
- wkup_m3 = "/ocp/wkup_m3@44d00000";
- elm = "/ocp/elm@48080000";
- tscadc = "/ocp/tscadc@44e0d000";
- am335x_adc = "/ocp/tscadc@44e0d000/adc";
- gpmc = "/ocp/gpmc@50000000";
- baseboard_beaglebone = "/bone_capemgr/baseboardmaps/board@0";
- baseboard_beaglebone_black = "/bone_capemgr/baseboardmaps/board@1";
- fb = "/fb@4830e000";
- hdmi = "/hdmi";
这个能解释得了许多我们已经看到的dts文件的target写法。
但同时，还会遇到如
这类的target。这里不妨再大胆假设下，OCP即片上外设，如果需要自己定义target，那么就在这个片段里边进行引脚等数据的定义。
- gpio-leds-cape-lcd7 {
- compatible = "gpio-leds";
- pinctrl-names = "default";
-
- pinctrl-0 = <&bone_lcd7_cape_led_00A3_pins>;
-
- lcd7-led0 {
- label = "lcd7:green:usr0";
- gpios = <&gpio2 28 0>;
- linux,default-trigger = "heartbeat";
- default-state = "off";
- };
总结起来就是：
1 常用的target都可用上表给出的
am33xx_pinmux epwmss1 i2c0 这些表示。
2 自定义引脚的意义及配置，通过新建一个包含
target = <&ocp> 的节点来实现。
不知理解是否有误，请拍砖指正。
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