[Skiboot] [PATCH 4/6] xive: Use io_complete() when changing the ESB mask bits

[Benjamin Herrenschmidt]

On Thu, 2017-12-07 at 12:47 +1100, Oliver wrote:
> On Thu, Dec 7, 2017 at 4:39 AM, Benjamin Herrenschmidt
> <benh at kernel.crashing.org> wrote:
> > Thus ensuring that the load has completed before anything else
> > is done (ie, the interrupt is actually masked).
> > 
> > Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> > ---
> >  hw/xive.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/xive.c b/hw/xive.c
> > index 76939b79..104e1e85 100644
> > --- a/hw/xive.c
> > +++ b/hw/xive.c
> > @@ -2451,7 +2451,7 @@ static void xive_update_irq_mask(struct xive_src *s, uint32_t idx, bool masked)
> >         if (s->flags & XIVE_SRC_SHIFT_BUG)
> >                 offset <<= 4;
> > 
> > -       in_be64(mmio_base + offset);
> > +       in_complete(in_be64(mmio_base + offset));
> 
> Can you elaborate a bit of what this is doing an why it needs to be done?

Well, the cset says it :-) Basically the twi/isync construct is the
same we use in the kernel in every in_* and it's supposed to make
the processor "consume" the load, and not execute past the isync until
the load value has returned.

Ben.

> 
> >  }
> > 
> >  static int64_t xive_sync(struct xive *x)
> > --
> > 2.14.3
> > 
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> 
> Tested-by: Oliver O'Halloran <oohall at gmail.com>