[U-Boot-Users] API for serial functions

[Wolfgang Denk <wd@denx.de>]

In message <200710010620.50106.vapier@gentoo.org> you wrote:
>
> i'm not claiming this is going to turn a 100mhz proc into 1000mhz proc or 
> something, but in the tail end of writing to the UART, you would free up the 
> CPU to continue ... and the processor tends to be a lot faster than the speed 
> of a UART, so it could chew through a sizable chunk of code before the UART 
> finishes shifting out a single byte ... and depending on the hardware, you
> could be talking about 1 byte, 5 bytes, or more

So you might end up saving 1 or 5 or a few more milliseconds.

> maybe ... you'd have to mess up the processor pretty bad such that it breaks 
> the peripherals ... the UART in a Blackfin acts independently of the core
> 
> > So I vote for not removing this transmitter empty check.
> 
> i'd note that this is pretty inconsistent across different ports ...

I agree with Stefan. Please don't change this. The current  implemen-
tation (wait until trasmit has completed) is what I prefer.

> so when do you return ?  after making sure the byte has moved from the core to 
> the peripheral hardware ?  after making sure the byte has started to be 
> shifted out from the peripheral onto the line ?  after making sure the byte
> has been completed shifted onto the line ?  the current Blackfin serial 
> driver exhibits the last -- it waits until the whole byte has gone through
> the whole process, from core through the line

If that's how it was implemented, then leave it that way. It's OK.

Best regards,

Wolfgang Denk

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