of_serial vs legacy serial support with powerpc arch on 405

Josh Boyer jwboyer at linux.vnet.ibm.com
Wed Mar 12 09:02:55 EST 2008

On Tue, 11 Mar 2008 09:04:27 -0600
"John Linn" <John.Linn at xilinx.com> wrote:

> I've searched and found some threads, but it's still not clear to me.
> I'm working on 405 with powerpc and trying to get UART550 working.

Walnut works.  So do Halakeau and Kilauea.  Is your serial port
significantly different from those?

> I know that I need speed, freq, and reg-shift properties in the device
> tree and I have found patches for of_serial.c.

Patches for of_serial.c for what?
> I still don't understand when to use of_serial.c (SERIAL_OF_PLATFORM) vs
> the legacy support for serial ports.  Is there any docs that I'm not
> finding that I should read?

There are no docs.  At one time, of_serial was declared as the one true
serial driver, but these days either will do.  The benefit of
legacy_serial is that output is enabled earlier in the boot.

> I don't see a way to configure in the legacy support, but I'm using
> SERIAL_OF and having problems. I don't see the console getting enabled
> even though it found the serial port driver.

You need to have CONFIG_PPC_UDBG_16550 set to bring in legacy_serial.


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