PROCESSOR-SDK-AM64X: need reffreence device tree node for GPS using i2c

please help me anybody 

Do you have any GPS module in mind you want to use? Usually GPS modules are connected through a serial/UART connection, there are several reference solutions that can be found online.

Andreas

Hi Andreas,

but we are using i2c GPS module.

can u please provide reference node how to configure in dts .

Thanks,

Naresh

Hi ,

inittially we connected GPS through UART1

but that is dedicated to firmware .

so we connected to i2c module

actually we observed that peripherals divided into 

1.main domain peripherals . 2.mcu domain peripherals 3. wakeup domain peripherals .

main_UART0
main_UART1  - Reserved

main_UART2
main_UART3
main_UART4
main_UART5
main_UART6
mcu_UART0 
wkup_UART0  - reserved

here UART1 is reserved so we connected GPS to i2c 

but in virtual file system it showing names as : uart0,urat1 ,urat2,urat3,urat4,urat5,urat6.

how did you find which is main domain ,wakeup ,mcu domain peripherlas by seeing nodes in virtual file system.

one method is we can find by disabling all uarts ...enabling each uart peripherals one by one .

is there any alternative methods ?

Hi Andreas ,

any update ?

Thanks,

Naresh

Naresh,

you can use the device tree (DTS) files to get an idea which uart is assigned to with domain and which /dev/ttySx.

a0797059@ula0797059:~/git/linux/arch/arm64/boot/dts/ti (ti-linux-5.10.y)
$ grep uart k3-am64*.dtsi
k3-am64.dtsi:		serial0 = &mcu_uart0;
k3-am64.dtsi:		serial1 = &mcu_uart1;
k3-am64.dtsi:		serial2 = &main_uart0;
k3-am64.dtsi:		serial3 = &main_uart1;
k3-am64.dtsi:		serial4 = &main_uart2;
k3-am64.dtsi:		serial5 = &main_uart3;
k3-am64.dtsi:		serial6 = &main_uart4;
k3-am64.dtsi:		serial7 = &main_uart5;
k3-am64.dtsi:		serial8 = &main_uart6;
k3-am64-main.dtsi:	main_uart0: serial@2800000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart1: serial@2810000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart2: serial@2820000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart3: serial@2830000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart4: serial@2840000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart5: serial@2850000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-main.dtsi:	main_uart6: serial@2860000 {
k3-am64-main.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-mcu.dtsi:	mcu_uart0: serial@4a00000 {
k3-am64-mcu.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";
k3-am64-mcu.dtsi:	mcu_uart1: serial@4a10000 {
k3-am64-mcu.dtsi:		compatible = "ti,am64-uart", "ti,am654-uart";

In the device tree alias section (the first part) the rule pretty much is serialX == /dev/ttySX. For example, on our AM64 demo boards, the "main" UART used for U-Boot/Linux is the MAIN_UART0 peripheral module. And it is aliased as serial2, hence it'll become /dev/ttyS2 in Linux. Note that this is the only UART that is enabled in the TI DTS files. If you want to use other UARTs you need to enable them and also assign the pinmux accordingly. It's not too hard to do, if you search the E2E and look at existing DTS files you can model after that.

If you want to parse the sysfw you can do it like below. First, enumerate all active UART modules (only one here). Note how the base address corresponds to the base address of MAIN_UART0 (see TRM). The inside the platform device you can see how it's associated with 'ttyS2' a.k.a. '/dev/ttyS2'.

root@am62xx-evm:/# ls -al /sys/bus/platform/devices/*.serial 
lrwxrwxrwx    1 root     root             0 Jun  6 19:14 /sys/bus/platform/devices/2800000.serial -> ../../../devices/platform/bus@f0000/2800000.serial

root@am62xx-evm:/# ls -al /sys/bus/platform/devices/bus@f0000/2800000.serial
drwxr-xr-x    4 root     root             0 Jun  6 19:14 .
drwxr-xr-x   36 root     root             0 Jun  6 19:14 ..
lrwxrwxrwx    1 root     root             0 Jun  6 19:18 driver -> ../../../../bus/platform/drivers/omap8250
-rw-r--r--    1 root     root          4096 Jun  6 19:18 driver_override
-r--r--r--    1 root     root          4096 Jun  6 19:18 modalias
lrwxrwxrwx    1 root     root             0 Jun  6 19:18 of_node -> ../../../../firmware/devicetree/base/bus@f0000/serial@2800000
drwxr-xr-x    2 root     root             0 Jun  6 19:18 power
lrwxrwxrwx    1 root     root             0 Jun  6 19:14 subsystem -> ../../../../bus/platform
drwxr-xr-x    3 root     root             0 Jun  6 19:14 tty
-rw-r--r--    1 root     root          4096 Jun  6 19:14 uevent

root@am62xx-evm:/# ls -al /sys/bus/platform/devices/bus@f0000/2800000.serial/tty
drwxr-xr-x    3 root     root             0 Jun  6 19:14 .
drwxr-xr-x    4 root     root             0 Jun  6 19:14 ..
drwxr-xr-x    3 root     root             0 Jun  6 19:14 ttyS2

Regards, Andreas

Hi ,

Thanks for your explanation  with the help of virtual system .

actually i am working on our customer board .

we should work on GPS which is connected to i2c 

could you please share steps to enable the GPS in kernel [ kernel configuration & device tree node for gps using i2c ].

Its easy for us to enable GPS using uart  but here we are going to enable GPS as a i2c device .

help me provide example nodes , in fast anybody enabled i2c GPS deivce ?

Thanks,

Naresh