Board bring-up part 3: Other peripherals
I'm currently working with a board bring up for a custom hardware based on a OMAPL138 from Texas Instruments. It is fun to work with "real" bring-ups. Most of my customers use System On Modules (SoM:s) these days. You get a lot for free with those modules but a lot of the fun is stripped away.
This post is not intended to be guide, it is more of a follow-me-through-my-work-post divided into three parts.
The first step is to get a bootloader to startup properly - which is also as far as I will take it in this series.
We are going to use U-boot [1] as bootloader for this project and I will use the TMDSLCDK138 [2] implementation as a reference during my bring-up, which is a evaluation kit for the OMAP-L138 CPU.
I will also be sharing lots of code snippets and it may not be obvious where they belong. In part4, I will summary all the changes I made.
About this part
In this part I will add support for the rest of the peripherals I need. The board has a lot of external IC:s that the final product shall support, but after looking into it, very few of those needs to be supported by the bootloader. Hence the only peripherals I will setup is the EMAC to add an ethernet interface and the serial port.
EMAC
I Added CONFIG_DRIVER_TI_EMAC=y to the configuration file, MUX the pins and setup the module to use MII mode:
1static const struct pinmux_config emac_pins[] = {
2 { pinmux(2), 8, 1 },
3 { pinmux(2), 8, 2 },
4 { pinmux(2), 8, 3 },
5 { pinmux(2), 8, 4 },
6 { pinmux(2), 8, 5 },
7 { pinmux(2), 8, 6 },
8 { pinmux(2), 8, 7 },
9 { pinmux(3), 8, 0 },
10 { pinmux(3), 8, 1 },
11 { pinmux(3), 8, 2 },
12 { pinmux(3), 8, 3 },
13 { pinmux(3), 8, 4 },
14 { pinmux(3), 8, 5 },
15 { pinmux(3), 8, 6 },
16 { pinmux(3), 8, 7 },
17 { pinmux(4), 8, 0 },
18 { pinmux(4), 8, 1 }
19};
20
21int board_init(void)
22{
23 ...
24 if (davinci_configure_pin_mux(emac_pins, ARRAY_SIZE(emac_pins)) != 0)
25 return 1;
26 davinci_emac_mii_mode_sel(HAS_RMII);
27
28 ...
29}A little bit redundant as we setup the pinctrl node in the devicetree as well.
Devicetree
Enable the mdio and eth0 nodes in the device tree.
&mdio {
pinctrl-names = "default";
pinctrl-0 = <&mdio_pins>;
bus_freq = <2200000>;
status = "okay";
};
ð0 {
pinctrl-names = "default";
pinctrl-0 = <&mii_pins>;
status = "okay";
};Serial port
Make sure CONFIG_SERIAL=y and CONFIG_DM_SERIAL=y in the configuration.
Devicetree
Enable the serial1 node in the device tree.
&serial1 {
pinctrl-names = "default";
pinctrl-0 = <&serial1_rxtx_pins>;
status = "okay";
};Summary
This was a short post, but we're getting close to the end now!
Continue to Part4 of this series.