i.MX ProcessorsのトピックRe: Having problem with ttyAMA0 serial console

Having problem with ttyAMA0 serial console

Jean-PaulLePape — Tue, 17 Jan 2012 12:16:17 GMT

Hello,

I'm using busybox and the kernel 3.2.1 on the i.MX28 EVK board. The serial console name change and it's now ttyAMA0 instead of ttyAM0.

So I needed to make a adjustment in the inittab file. Now I have the following line in the inittab file:

ttyAMA0::respawn:/sbin/getty -L ttyAMA0 115200 vt100

When the system finises booting, I will the following error message:

can't open /dev/ttyAMA0: No such device or address

I created the device node by using this command:

mknod -m 666 ttyAMA0 c 204 16

Does anybody knows what the problem is?

Thanks for your help,

:-)

Re: Having problem with ttyAMA0 serial console

netstv — Tue, 17 Jan 2012 12:56:35 GMT

we start up our getty's a little different (using busybox's srvctrl functionality) but the params I pass in are this.

/sbin/getty -L 11520 /dev/ttyAMA0 console

That works for us.

So the other question is, does y our mknod actually work and create the /dev/ttyAMA0 device? Can you ssh or telnet into the device to see what the state of your filesystem is?

Re: Having problem with ttyAMA0 serial console

Jean-PaulLePape — Wed, 18 Jan 2012 00:28:46 GMT

Hi Steve,

It works now but the problem was coming from device node (As you suspected). The correct command to create the device node is:

mknod ttyAMA0 c 204 64

Thanks for your help,

:-)

Steve Iribarne said:

we start up our getty's a little different (using busybox's srvctrl functionality) but the params I pass in are this.
/sbin/getty -L 11520 /dev/ttyAMA0 console
That works for us.
So the other question is, does y our mknod actually work and create the /dev/ttyAMA0 device? Can you ssh or telnet into the device to see what the state of your filesystem is?

Re: Having problem with ttyAMA0 serial console

RobertSchwebel — Tue, 24 Jan 2012 13:49:20 GMT

I don't know how you build your root filesystem, but maybe booting with 'init=/bin/sh' and looking around in the filesystem might help you to find the bug.

Does the serial interface work after you have created the device node manually? If yes, you could add the node to your root filesystem permanently (or instruct your build system to do so). Our usual recommendation is to use devtmpfs for any modern kernel, because it creates the device nodes automatically for you.

rsc

Re: Having problem with ttyAMA0 serial console

Jean-PaulLePape — Thu, 24 May 2012 09:02:02 GMT

Hi,

Sorry for the delay, was working on something else. Yes it does work when I create manually the device node. We are using udev on the system.

Would you have any example of dynamically/automatically creating the node with devtmpfs.

Thanks