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Date: Mon, 26 Feb 2007 14:12:22 -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.

Mucho gracias.

> 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.

Hmm, he must have been talking about BSD.  But adding it to BSD
couldn't have been that hard since he had the Linux driver to look at.
Although maybe he didn't think to check Linux at the time.

> 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.
> 
> 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!

Thanks, I'm good for now.

Cheers,

a

> 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
> > 
