[U-Boot] [PATCH v4 2/2] NS16550: buffer reads

[Wolfgang Denk]

Dear Simon Glass,

In message <CAPnjgZ2Q3XtGK=5HhF0KhQo4XQDA6CAH3QFKfmgCwzNV_y0mUA at mail.gmail.com> you wrote:
> 
> > Hmm... What about the conversation around V2 of the patch re: using XOFF/XON
> > to control input flow? IIUC, even this V4 patch would not help much if there
> > is a command within the pasted code that sends a lot of output, right?
>
> Well it will help so long as there isn't much more input. Perhaps the

Don't you see that this "as long as there isn't much more input" is
the fatal flaw of your patch?  You are not fixing the problem, you are
just extending the point wher eit hits to some extend - it may work
for a few more situations, but it's still guaranteed to fail for
others.

> To address your question, I think we did discuss it. Wolfgang felt
> that it should be as simple as sending XOFF when receiving the end of
> a line and XON when waiting for characters on the new line. It
> certainly sounds plausible.

Then please let's take this approach instead, if you really need to
support such a mode of operation.

> I have other reasons for favouring this patch. On the main hardware
> platform I currently use, SPI and the console UART are multiplexed, so
> before using SPI (e.g. saveenv, reading the environment) we must read
> in any pending characters to avoid corruption. After re-enabling the
> UART later we must clear out any junk that has arrived. This patch
> provides a way around that which XON/XOFF does not (since when you
> send XOFF you may already have input characters outstanding - junk
> will later be added and you can't tell the difference).

That's an unrelated hardware issue that needs to be addressed
independently.

Best regards,

Wolfgang Denk

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