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Re: [Qemu-devel] [RFC v4 4/5] hw/arm/digic: add UART support

From: Antony Pavlov
Subject: Re: [Qemu-devel] [RFC v4 4/5] hw/arm/digic: add UART support
Date: Fri, 6 Sep 2013 17:00:15 +0400

On Fri, 6 Sep 2013 08:25:20 +0100
Peter Maydell <address@hidden> wrote:

> On 6 September 2013 07:54, Antony Pavlov <address@hidden> wrote:
> > On Thu, 5 Sep 2013 19:17:50 +0100
> > Peter Maydell <address@hidden> wrote:
> >> Does this UART really not have a FIFO?
> >
> > There is no public documentation on Digic chips.
> > Only Canon's engineers know something about Digic's FIFO (if it exists :).
> You can deduce its existence though -- does the
> UART let you feed two or three characters to it
> at faster than whatever the serial line speed is
> before it sets the "stop sending me bits" status
> bit, or does it stop after the first?

No, I can't :)

How can I check this mysterious "stop sending me bits" status bit?
Do you mean the UART hardware flow control pin?
I can't use hardware flow control as I have only 3-wire UART on the camera.
Moreover I have to enable hardware flow control in software, but I have
no information how to do it.

> If the real firmware uses this for anything remotely
> serious (ie for more than trivial and default-disabled
> debug info) it probably does have a FIFO. However,
> let's assume it doesn't for now.
> -- PMM

Best regards,
  Antony Pavlov

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