带有Pandaboard和Arch Linux的UART4 [英] UART4 with Pandaboard and Arch Linux
问题描述
我试图在Arch Linux的Pandaboard中使用UART4.我正在使用最新的内核(4.2.0-2-ARCH)，所以无法使用omap_mux来以旧方式配置MUX，而必须使用设备树覆盖来进行.这对我来说是新的，所以很难，我以前从未做过.我一直在阅读有关如何在诸如 this 和此 .因此，我下载了OMAP4技术参考手册(在此处下载). 表18-504 显示了UART4控制寄存器.基于上述内容和上面的网址，我创建并编译了以下设备树叠加层，将寄存器填充为0，这应将MUX设置为UART4功能:
I'm trying to use UART4 in my Pandaboard with Arch Linux. I'm using the latest kernel (4.2.0-2-ARCH) so I can't configure MUX in the old way using omap_mux, I have to do it using Device Tree Overlay. This is new to me so it's hard, I've never done this before. I have been reading some post about how to use them in Beaglebone boards in sites like this and this. So I downloaded the OMAP4 Technical Reference Manual (download here). Table 18-504 shows the UART4 control register. Based on that and the urls above I created and compiled the following Device Tree Overlay filling the register with 0's, this should set the MUX for UART4 functionality:
// Util: http://lxr.free-electrons.com/source/arch/arm/boot/dts/omap4-panda-es.dts
// http://www.valvers.com/embedded-linux/beaglebone-black/step04-gpio/
/dts-v1/;
/plugin/;
/ {
model = "TI OMAP4 PandaBoard-ES";
compatible = "ti,omap4-panda-es", "ti,omap4460";
part-number = "ANDRES-IO";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
uart4_pins: pinmux_uart4_pins {
pinctrl-single,pins = <
0x15C 0x00 // kernel pin 142 (uart4 tx y rx - address 0x4A10 015C)
>;
};
};
};
fragment@1 {
target = <&ocp>;
__overlay__ {
uart4_pins_helper {
compatible = "panda-pinmux-helper";
pinctrl-names = "default";
pinctrl-0 = <&uart4_pins>;
status = "okay";
};
};
};
};
我将编译后的文件复制到/lib/firmware/中，但是之后我不知道如何使用或启用它. Beaglebone板具有bone_capemgr，但在Pandaboard中看不到这种东西.
I copied the compiled file to /lib/firmware/ but after that I don't know how to use or enable it. Beaglebone boards have bone_capemgr but I can't see such a thing in Pandaboard.
其他操作系统(如Ubuntu)已经配置了UART4，我尝试查找它们使用的设备树叠加层，但找不到任何东西.
Other OS like Ubuntu has UART4 already configured, I tried looking for the Device Tree Overlay they use but couldn't find anything.
推荐答案
我解决了！！！！也许有些琐碎，但对我来说真的很难，我学到了很多东西.仅在Beagleboards中，在Pandaboard中没有有关如何执行此操作的太多信息.所以首先，Device Tree Overlay文件仅在引导时加载，我们无法像Beagleboard一样动态加载它，因为我们没有bone_capemgr.编译后的.dtb文件位于/boot/dtbs中(至少在Arch Linux中)，那里有很多.dtb文件，但是在启动时取决于板子只有一个被加载，并且您可以看到在加载时哪个文件被加载了.引导，例如，在我的情况下是:
I solved it!!!!! Maybe is something trivial but it was really hard for me and I learned a lot. There is no much info about how to do it in Pandaboard, just for Beagleboards. So first, the Device Tree Overlay file it's loaded only at boot, we can't load it dynamically as with Beagleboard because we don't have a bone_capemgr. The compiled .dtb file is located in /boot/dtbs (at least in Arch Linux), there are a lot of .dtb files there but only one is loaded at boot depending on the board and you can see which one is loaded when booting, for example, in my case it is:
U-Boot 2015.04 (Jun 07 2015 - 19:26:06) Arch Linux ARM
CPU : OMAP4460 ES1.1
Board: OMAP4 Panda
I2C: ready
DRAM: 1 GiB
MMC: OMAP SD/MMC: 0
** Unable to use mmc 0:1 for loading the env **
Using default environment
Net: No ethernet found.
Hit any key to stop autoboot: 0
starting USB...
USB0: USB EHCI 1.00
scanning bus 0 for devices... 3 USB Device(s) found
scanning usb for storage devices... 0 Storage Device(s) found
scanning usb for ethernet devices... 1 Ethernet Device(s) found
switch to partitions #0, OK
mmc0 is current device
mmc found on device 0
Checking for: /boot/uEnv.txt ...
74 bytes read in 13 ms (4.9 KiB/s)
Loaded environment from /boot/uEnv.txt
Checking if uenvcmd is set ...
4984312 bytes read in 244 ms (19.5 MiB/s)
loading /boot/dtbs/omap4-panda-es.dtb ...
100695 bytes read in 380 ms (257.8 KiB/s)
** File not found /boot/initramfs-linux.img **
Kernel image @ 0x82000000 [ 0x000000 - 0x4c0df8 ]
## Flattened Device Tree blob at 88000000
Booting using the fdt blob at 0x88000000
Loading Device Tree to 8ffe4000, end 8ffff956 ... OK
Starting kernel ...
我有一个Pandaboard ES，所以加载的文件是/boot/dtbs/omap4-panda-es.dtb.我对该文件进行了反编译，因此可以使用dtc -I dtb -O dts omap4-panda-es.dtb > omap4-panda-es.dts添加UART4 MUX设置(取自此处是关于pinctrl-single,pins的一个很好的解释:
I have a Pandaboard ES so the loaded file is /boot/dtbs/omap4-panda-es.dtb. I decompiled the file so I can add the UART4 MUX settings using dtc -I dtb -O dts omap4-panda-es.dtb > omap4-panda-es.dts (taken from here). So now we have a omap4-panda-es.dts which is the complete Device Tree Overlays that sets everything up, I just need to add the UART4 MUX settings. We have to use the pinctrl-single,pins property. Here is a really good explanation about pinctrl-single,pins:
pinctrl-single的引脚配置节点指定为 pinctrl使用pinctrl-single，pins寄存器偏移和值对. 仅更新pinctrl-single，function-mask中指定的位. 例如，可以使用以下方法设置设备的引脚: pinctrl-single，pins =< 0xdc 0x118>;其中0xdc是相对于 设备pinctrl寄存器的pinctrl寄存器基址，以及 0x118包含所需的pinctrl寄存器值.
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.
这是我一开始就误解的东西，尽管pinctrl地址是绝对的，但它相对于树中的基地址.以我为例，有很多pinmux_tfp410_pins，pinmux_dss_hdmi_pins，pinmux_i2c1_pins等.所有这些pinmux_*都位于名为pinmux@40的父项下，这意味着pinctrl中指定的地址是相对的到0x40，但是此pinmux@40在另一个名为scm@100000的节点下，该节点在另一个名为l4@4a000000的节点内，因此pinmux@40内的地址相对于该节点的基址，即该基址的总和这些地址，即0x4a000000 + 0x100000 + 0x40 = 0x4a100040，所以0xa100040是基地址，在pinctrl中指定的所有地址都是相对于0xa100040的.因此，根据OMAP4 Technical Reference Manual中的表18-504 (可下载此处).所以我在节点pinmux@40下添加了这个:
This was something I misunderstood at the beginning, I though the pinctrl address was absolute but it's relative to the base address in the tree. In my case for example there are a lot of pinmux_tfp410_pins, pinmux_dss_hdmi_pins, pinmux_i2c1_pins, etc. All these pinmux_* are under a parent called pinmux@40, that means that the address specified in pinctrl is relative to 0x40, but this pinmux@40 is under another node called scm@100000 which is inside another node called l4@4a000000, so the addresses inside pinmux@40 are relative to the base address of the node that is the sum of all these addresses, that is 0x4a000000 + 0x100000 + 0x40 = 0x4a100040, so 0xa100040 is the base address, all the address specified in pinctrl are relative to 0xa100040. So, according to Table 18-504 in the OMAP4 Technical Reference Manual (download available here) the address for the UART4 control register that control the MUX and some other things is 0x4A10015C. The base address of pinctrl is 0x4a100040 so the address we must specify in pinctrl is 0x11c because 0x4a100040 + 0x11c = 0x4A10015C. All the Device Tree Overlays I found of other linux distros that support Pandaboard use the same base address 0x4a100040 (here for example). So I added under the node pinmux@40 this:
// Set the UART4 MUX, it doesn't come by default so I had to add it
// "linux,phandle" has the same value aas "phandle", it's just a reference number, just make sure
// it is not being used in another part of the tree (it will refuse to compile if you do it wrong)
// The phandle is used for reference in "serial@4806e000" at "pinctrl-0"
pinmux_uart4_pins {
pinctrl-single,pins = <
0x11c 0x100 // uart4_rx.uart4_rx INPUT | MODE0
0x11e 0 // uart4_tx.uart4_tx OUTPUT | MODE0
>;
linux,phandle = <0xfff>;
phandle = <0xfff>;
};
I took this settings from here but just changing the 0x100 and 0 will change the settings in the register. In my case I also had to add:
linux,phandle = <0xfff>;
phandle = <0xfff>;
例如，我在Ubuntu中看不到此文件( https://github.com/Canonical-kernel/Ubuntu-kernel/blob/master/arch/arm/boot/dts/omap4.dtsi )，但我不知道为什么或phandle的目的是什么，我只知道是否将它们用作参考，我需要在设备树中的其他地方放置一个参考，只需确保它是唯一的即可，它可以是任何32位值，但在树内必须唯一.在我的情况下，还有另一个引用UART4的节点:
I don't see this in Ubuntu for example (https://github.com/Canonical-kernel/Ubuntu-kernel/blob/master/arch/arm/boot/dts/omap4.dtsi) but I don't know why or what is the purpose of this phandle, all I know if that they are used as a reference, a reference I need to put somewhere else in the Device Tree, just make sure it is unique, it can be any 32-bit value but must be unique inside the tree. In my case there was another node referring UART4:
serial@4806e000 {
compatible = "ti,omap4-uart";
reg = <0x4806e000 0x100>;
interrupts = <0x0 0x46 0x4>;
ti,hwmods = "uart4";
clock-frequency = <0x2dc6c00>;
interrupts-extended = <0x1 0x0 0x46 0x4 0x82 0x11c>;
linux,phandle = <0x121>;
phandle = <0x121>;
};
所以我不得不使用phandle，否则将不会应用MUX设置:
So there I had to use phandle otherwise MUX settings won't be applied:
serial@4806e000 {
compatible = "ti,omap4-uart";
reg = <0x4806e000 0x100>;
interrupts = <0x0 0x46 0x4>;
ti,hwmods = "uart4";
pinctrl-names = "default";
pinctrl-0 = <0xfff>;
clock-frequency = <0x2dc6c00>;
interrupts-extended = <0x1 0x0 0x46 0x4 0x82 0x11c>;
linux,phandle = <0x121>;
phandle = <0x121>;
};
最后，在文件末尾有很多定义，例如，每个节点一个.
Finally, at the end of the file there a lot of definitions, one for each node, for example
i2c1_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_i2c1_pins";
i2c2_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_i2c2_pins";
i2c3_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_i2c3_pins";
i2c4_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_i2c4_pins";
wl12xx_gpio = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_wl12xx_gpio";
wl12xx_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_wl12xx_pins";
twl6030_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_twl6030_pins";
它们只是描述每个节点的位置，在这里我们可以清楚地看到基地址是什么.所以我在这里添加了这个:
They just describe where each node is located, here we can clearly see what the base address is. So here I just added this:
uart4_pins = "/ocp/l4@4a000000/scm@100000/pinmux@40/pinmux_uart4_pins";
现在我们有了一个完整的.dts文件，该文件应能使UART4正常工作.我们必须使用dtc -O dtb -o omap4-panda-es.dtb -b O -@ omap4-panda-es.dts对其进行编译，这将生成一个.dtb文件，该文件将替换/boot/dtbs中的文件，因此请替换并重新启动！重新启动运行cat /sys/kernel/debug/pinctrl/4a100040.pinmux/pinmux-functions后，它应显示以下内容:
Now we have a complete .dts file which should get the UART4 working. We must compile it using dtc -O dtb -o omap4-panda-es.dtb -b O -@ omap4-panda-es.dts, this will generate a .dtb file that will replace the one in /boot/dtbs, so replace it and reboot! After rebooting run cat /sys/kernel/debug/pinctrl/4a100040.pinmux/pinmux-functions, it should show something like this:
function: pinmux_dss_dpi_pins, groups = [ pinmux_dss_dpi_pins ]
function: pinmux_tfp410_pins, groups = [ pinmux_tfp410_pins ]
function: pinmux_dss_hdmi_pins, groups = [ pinmux_dss_hdmi_pins ]
function: pinmux_tpd12s015_pins, groups = [ pinmux_tpd12s015_pins ]
function: pinmux_hsusbb1_pins, groups = [ pinmux_hsusbb1_pins ]
function: pinmux_uart4_pins, groups = [ pinmux_uart4_pins ]
function: pinmux_wl12xx_pins, groups = [ pinmux_wl12xx_pins ]
function: gpio_led_pmx, groups = [ gpio_led_pmx ]
function: pinmux_wl12xx_gpio, groups = [ pinmux_wl12xx_gpio ]
function: pinmux_i2c1_pins, groups = [ pinmux_i2c1_pins ]
function: pinmux_twl6030_pins, groups = [ pinmux_twl6030_pins ]
function: pinmux_twl6040_pins, groups = [ pinmux_twl6040_pins ]
function: pinmux_i2c2_pins, groups = [ pinmux_i2c2_pins ]
function: pinmux_i2c3_pins, groups = [ pinmux_i2c3_pins ]
function: pinmux_i2c4_pins, groups = [ pinmux_i2c4_pins ]
function: pinmux_wl12xx_pins, groups = [ pinmux_wl12xx_pins ]
function: pinmux_mcpdm_pins, groups = [ pinmux_mcpdm_pins ]
function: pinmux_mcbsp1_pins, groups = [ pinmux_mcbsp1_pins ]
如果我们看到uart4，一切都很好，应该可以正常工作！否则.dts文件中有问题.我们可以通过运行例如echo -e "AT" > /dev/ttyO3来测试uart是否正常工作，请记住/dev/ttyO3是UART4.我希望这对某人有用！
If we see uart4 everything is fine and it should be working! Otherwise there is something wrong in the .dts file. We can test if the uart is working by running for example echo -e "AT" > /dev/ttyO3, remember that /dev/ttyO3 is UART4. I hope this will be useful for someone!
这里仅作参考，是完整的.dts和已编译的.dtb文件，具有可用的UART4: https://gist.github.com/dragondgold/1aaabf93279006b703f3
Just for reference here is the complete .dts and compiled .dtb file with working UART4: https://gist.github.com/dragondgold/1aaabf93279006b703f3
这篇关于带有Pandaboard和Arch Linux的UART4的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
