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
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