From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfgang Denk <wd@denx.de>
Date: Mon, 01 Oct 2007 12:37:57 +0200
Subject: [U-Boot-Users] API for serial functions
In-Reply-To: Your message of "Mon, 01 Oct 2007 05:41:28 EDT."
	<200710010541.29574.vapier@gentoo.org>
Message-ID: <20071001103757.535BC2408A@gemini.denx.de>
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To: u-boot@lists.denx.de

In message <200710010541.29574.vapier@gentoo.org> you wrote:
>
> > While it's not a strict requirement, I would  expect  that  you  wait
> > until the charatcer has been sent. You have toi add some wait anway -
> > either  at  the  start  or  at  the end of the function, and from the
> > debugging point of view it makes more sense to  wait  for  completion
> > before  continuing.  Performancewise  there  will be no difference, I
> > think.
> 
> the optimal performance method would be at the start of serial_putc(), spin
> until a byte has opened up in the hardware fifo, and then queue it up and 

Maybe. But in reality, you won;t be able to see a differecne in
performance.

But the code will be more complicated and have a higher footprint,
which both is a con.

> then in the serial_setbrg() function (what does "brg" stand for anyways?),

Baud Rate Generator. This origins from the initial implementation on
MPC8xx systems...

> the current Blackfin serial driver posts a character into the fifo and then 
> spins until both the fifo and the transmit register is empty ... if there is 

I like this implementation. It's simple and straightforward, and you
can rely on that the user has seen the caratcer on the line before the
function returns. That's a good thing for initial debugging (board
bring up).

> no higher level API dictacting the requirement (and my quick tests here seem 
> to back that up), then i'll just scrub the code and gain a little bit of 

Please don't.

> speed and lose a few bytes in code size :)

Reduce code size? To me it seems the changes you described above would
take more code.

Best regards,

Wolfgang Denk

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