of_serial vs legacy serial support with powerpc arch on 405

[John Linn]

Thanks for the help Josh.  I made some comments in-line.


-----Original Message-----
From: Josh Boyer [mailto:jwboyer at linux.vnet.ibm.com] 
Sent: Tuesday, March 11, 2008 4:03 PM
To: John Linn
Cc: linuxppc-dev at ozlabs.org
Subject: Re: of_serial vs legacy serial support with powerpc arch on 405

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?

>> Requires a shift as the regs are farther apart.

> 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?

>> There was a patch to correct where the spd was assumed to be in the 
>> device tree and it would bomb out if it wasn't. I was thinking there
was
>> a patch for the reg-shift value also.
 
> 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.

>> Thanks got it working with some mods.

josh