of_serial vs legacy serial support with powerpc arch on 405

Stephen Neuendorffer stephen.neuendorffer at xilinx.com
Wed Mar 12 09:14:45 EST 2008


Josh,

Specifically, we're trying to get console on of_serial, but there
doesn't seem to be any code to register a console, except in
legacy_serial?  But legacy_serial doesn't implement the offsets
necessary for the Xilinx uart16550 cores.  Does it seem reasonable to
add code to of_serial.c to register consoles, or is there something else
we're missing here?

Steve

> -----Original Message-----
> From: linuxppc-dev-bounces+stephen.neuendorffer=xilinx.com at ozlabs.org
[mailto:linuxppc-dev-
> bounces+stephen.neuendorffer=xilinx.com at ozlabs.org] On Behalf Of Josh
Boyer
> Sent: Tuesday, March 11, 2008 3:03 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?
> 
> > 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.
> 
> josh
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