Re: performance-improvement-of-serial-console-via-virtual.patch added to -mm tree

["Hironobu Ishii" <hishii@soft.fujitsu.com>]

Hi Russel,
> 
> The problem is that the console write method may be called prior to
> autoconfig() being run for the port in question, so tx_loadsz may be
> uninitialised.

Thank you for explanation.

>> > * if it has been initialised
>> > * how much data is already contained in the FIFO
>> 
>> Right, we can't know how many byte exist in the FIFO.
>> So this patch is waiting the FIFO becomes empty at first
>> by calling "wait_for_xmitr(up)".
>> (This is the same logic with original.)
>> 
>> After TX FIFO become empty, we can decide the available 
>> TX FIFO depth by up->tx_loadsize.
> 
> Only if you ignore the fact that tx_loadsz may not be initialised.

OK.
Before initialization, does tx_loadsz left 0?
If so, we can easily solve the problem:

   tx_loadsz = (up->tx_loadsz ? up->tx_loadsz : 1); <-----
   for (i = 0; i < count; ) {
           int     fifo;

           wait_for_xmitr(up);
           fifo = tx_loadsz;        <------
            .
            .
            .


Best regards,
Hironobu Ishii