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Date: Thu, 1 Mar 2007 19:32:12 -0800
From: Andrew Sharp <andy.sharp@onstor.com>
To: "Brian Stark" <brian.stark@onstor.com>
Subject: Re: the last serial port question
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On Mon, 26 Feb 2007 13:47:53 -0800 "Brian Stark"
<brian.stark@onstor.com> wrote:

> Andy,
> 
> Let me put it down on paper and see if that helps.
> 
> The RM9K has serial port support via 2 different chips.  The first is
> the Marvell system controller that provides 2 ports, and one of these
> ports is routed to the DB9 on the frontpanel.  The downside is that
> memory must be working because the UARTs use descriptors and buffers.
> Another downside is support for this UART has been lacking in OS
> distributions, so the support had to be developed by us (at least this
> is what Dan claimed).  There is limited support for a more traditional
> register-based scheme, but there is no FIFO support to go along with
> this so we can't use it in normal operation.  I believe that the PROM
> and possibly BSD rely on this mode to some extent at the beginning of
> boot-up, but they then switch over to the descriptor and buffer
> scheme.
> 
> The second UART supported on Bobcat is the very common Philips
> 16C2552. This was added on Rev 2 Bobcats for gdb sessions and is
> memory-mapped at 0xbf200000.  The idea is that one of the UARTs is
> dedicated for the SSC and the other for the FC core, although this is
> completely arbitrary and can be changed by software.  At the moment,
> I don't believe we use this for the SSC at all, but it is by the FC.
> If you type 'debug' at the FC prompt, one of the 552 ports is then
> targeted for gdb.

This function though is done by the PROM, right?  I'm trying to figure
out if I should be configuring support for these ports into the Linux
kernel.  I could make support for them a compile time directive if
kernel support for them isn't always needed.

> 
> Since the Marvell UART has less OS support and requires memory, it may
> be easier to use the Philips UART instead for development and then
> eventually transition to the Marvell.  If you want to go down that
> path, then the frontpanel DB9 can't be used for the SSC console.  You
> would need to use the header marked J7201 or J7202, which most boxes
> have brought out to the front via ribbon cables.  We may also have to
> provide some different PROM support for you, but this shouldn't be
> that bad since the PROM already sets up the Philips UART in case it's
> needed for gdb.
> 
> As it stands right now, here's how all of the consoles are laid out:
> 
> Header	Description			Board Location
> J1101		FP Core 0			Back right
> J1102		FP Core 1			Back right
> J2501		TXRX Core 0			Middle center
> J2502		TXRX Core 1			Middle center
> J5904		SSC				Back center,
> frontpanel DB9
> J5905		FC				Back center
> J7201		Debug SSC			Front right
> J7202		Debug FC			Front right
> 
> 
> Call me if you have questions!
> 
> 
> Brian
>   
> 
> > -----Original Message-----
> > From: Andy Sharp 
> > Sent: Monday, February 26, 2007 10:02 AM
> > To: Brian Stark
> > Subject: the last serial port question
> > 
> > I've only asked this three times before, so that means that 
> > this time I will remember the answer, I swear.
> > 
> > The serial port/console layout on bobcat.  Can you explain it 
> > to me again?  Feel free to call me, I've got pen and paper 
> > standing by to take notes.
> > 
> > Cheers,
> > 
> > a
> > 
