unable to enable UART2 on BBB.

Madhu K

unread,

Mar 19, 2017, 6:22:18 AM3/19/17

to BeagleBoard

HI All,

I am trying to enable UART2 on beaglebone black.

I have made below changes in am335x-bone-common.dtsi file but I am not able to see any prints related to UART2 in dmesg logs.

        uart2_pins: uart2_pins {
                pinctrl-single,pins = <
                        AM33XX_IOPAD(0x954, PIN_OUTPUT_PULLDOWN | MUX_MODE1) /* spi0_d0.uart2_tx */
                        AM33XX_IOPAD(0x950, PIN_INPUT_PULLUP | MUX_MODE1) /* spi0_sclk.uart2_rx */
                >;
        };

&uart2 {
        pinctrl-names = "default";
        pinctrl-0 = <&uart2_pins>;

        compatible = "free-electrons, serial";

        status = "okay";
};

I recompiled the dts file and generated new dtb, and loaded this dtb file. but no luck.

when I grep for the uart's in dmesg log it showing only one uart

ubuntu@ubuntu-armhf:~$ dmesg | grep uart
[    0.526979] omap_uart 44e09000.serial: no wakeirq for uart0

what could be issue.

Thanks & regards,
Madhu

Robert Nelson

unread,

Mar 19, 2017, 4:29:52 PM3/19/17

to Beagle Board, Madhu K

On Sun, Mar 19, 2017 at 5:22 AM, Madhu K <madhu...@gmail.com> wrote:
> HI All,
>
> I am trying to enable UART2 on beaglebone black.
>
> I have made below changes in am335x-bone-common.dtsi file but I am not able
> to see any prints related to UART2 in dmesg logs.
>
>
> uart2_pins: uart2_pins {
> pinctrl-single,pins = <
> AM33XX_IOPAD(0x954, PIN_OUTPUT_PULLDOWN | MUX_MODE1)
> /* spi0_d0.uart2_tx */
> AM33XX_IOPAD(0x950, PIN_INPUT_PULLUP | MUX_MODE1) /*
> spi0_sclk.uart2_rx */
> >;
> };
>
> &uart2 {
> pinctrl-names = "default";
> pinctrl-0 = <&uart2_pins>;
>
> compatible = "free-electrons, serial";

this is wrong ^ remove the compatible line..

>
> status = "okay";
> };
>
>
> I recompiled the dts file and generated new dtb, and loaded this dtb file.
> but no luck.
>
> when I grep for the uart's in dmesg log it showing only one uart
>
> ubuntu@ubuntu-armhf:~$ dmesg | grep uart
> [ 0.526979] omap_uart 44e09000.serial: no wakeirq for uart0
>
>
> what could be issue.

Regards,

--
Robert Nelson
https://rcn-ee.com/

Robert Nelson

unread,

Mar 20, 2017, 10:17:27 AM3/20/17

to Madhu K, Beagle Board

On Sun, Mar 19, 2017 at 11:37 PM, Madhu K <madhu...@gmail.com> wrote:
> Hi Robert,
>
> Can I know the reason why I have to remove compatible string?

Well because it's wrong for this hardware, and you are overwriting the
actual compatible string:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am33xx.dtsi#n285

Reply all

Reply to author

Forward