Re: [PATCH edk2-platforms 3/3] Silicon/SynQuacer: add support for DEBUG output on second UART

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> Date: Fri, 11 Jan 2019 17:58:44 +0000
> From: Leif Lindholm <leif.lindholm@linaro.org>
> 
> On Wed, Dec 26, 2018 at 02:25:30PM +0100, Ard Biesheuvel wrote:
> > On headless server systems where the PL011 serial port is the primary
> > console, having DEBUG output on the same port can be annoying, since
> > DEBUG output gets lost when the console driver clears the screen or
> > positions the cursor using control characters.
> > 
> > So add the ability to emit the DEBUG output on the DesignWare FUART
> > (which is exposed via the LS connector on DeveloperBox)
> 
> >From what I can tell, the DesignWare component is 8250-compatible, yet
> here we're using the 16550 driver. I presume this makes no difference
> for how we're using it, but could you add a comment to this effect to
> the commit message? (If the FUART is indeed a 16550 clone, please add
> a statement to that effect instead.)

The DesignWare component is (largely) 16550-compatible.  But the
FIFO's are optional and if they're not included you'll end up with
something that's probably closer to an 16450.  I suspect in most cases
SoC designers will include the FIFO's though since without them you
really can't use the port at anything but the slowest speeds.

Cheers,

Mark