[PATCH 01/16 v2] pmac_zilog: fix unexpected irq

[Finn Thain]

On Tue, 6 Dec 2011, Geert Uytterhoeven wrote:

> Hi Finn,
> 
> On Tue, Dec 6, 2011 at 16:13, Finn Thain <fthain at telegraphics.com.au> wrote:
> > +static void pmz_interrupt_control(struct uart_pmac_port *uap, int enable)
> > +{
> > +       if (enable) {
> > +               uap->curregs[1] |= INT_ALL_Rx | TxINT_ENAB;
> > +               if (!ZS_IS_EXTCLK(uap))
> > +                       uap->curregs[1] |= EXT_INT_ENAB;
> > +       } else {
> > +               uap->curregs[1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
> 
> Should there be a call to zssync() here?

I don't think so. Though I should have mentioned the change in the patch 
header.

> The old code always did that after disabling interrupts.

pmz_load_zsregs(), pmz_set_termios() and pmz_suspend() don't do it.

sunzilog only does it on sparc64 and only when writing to the data 
register or writing command modifiers to the control register ("On 64-bit 
sparc we only need to flush single writes to ensure completion.")

I can't find any purpose for control register reads in the chip manual.

The zssync() calls following some WR1 writes originate here: 
http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commitdiff;h=9e9d9f693c7def3900725c04c6b64311655eea51

So I don't see any need for control register reads but hopefully Ben can 
say for sure.

Reading the patch now I notice that I dropped a pmz_maybe_update_regs() or 
pmz_load_zsregs() in the suspend path. I will send a new patch.

Finn

> 
> > +       }
> > +       write_zsreg(uap, R1, uap->curregs[1]);
> > +}
> > +
> >  static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap)
> >  {
> >        struct tty_struct *tty = NULL;
> > @@ -339,9 +351,7 @@ static struct tty_struct *pmz_receive_ch
> >
> >        return tty;
> >  flood:
> > -       uap->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
> > -       write_zsreg(uap, R1, uap->curregs[R1]);
> > -       zssync(uap);
> 
> Cfr. e.g. here.
> 
> > +       pmz_interrupt_control(uap, 0);
> >        pmz_error("pmz: rx irq flood !\n");
> >        return tty;
> >  }
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
>