Question regarding ns16550

[Sebastian Huber]

On 23/10/14 18:12, Daniel Gutson wrote:
> On Thu, Oct 23, 2014 at 5:47 AM, Sebastian Huber
> <sebastian.huber at embedded-brains.de>  wrote:
>> >Hello Daniel,
> Hi Sebastian,
>
>> >
>> >I never notice a problem with this driver.  It should only write to the FIFO
>> >in case it is completely empty.  Did you observe problems?
> no, I didn't (actually I found this while looking for a serial bug
> which turned out to be due
> to a different cause).
> However, I notice that this isn't like what the polling write does (of
> course I'm not talking
> about the polling/interrput difference, but when writing byte-per-byte
> to the FIFO, I think
> both methods should do the same).
> IOW, what happens if the 'for' loop is too fast for the device? Will
> the latter be able to
> put the char in the FIFO and be ready for the next one? Isn't
> SP_LSR_THOLD exactly
> to tell whether the device' FIFO is ready to accept the next byte?
> Writing to the FIFO when it's completely empty is not the problem I
> see since it is
> guaranteed by the interrupt. My concern is different: it's whether the
> FIFO is filled too fast
> for the device.
>
>

Its not clear to me from the documentation if this is really necessary.  I 
never noticed problems on several targets with this driver.

-- 
Sebastian Huber, embedded brains GmbH

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