Re: [PATCH 4/4] pnv/xive2: Handle TIMA access through all ports

[Frederic Barrat]

On 30/05/2023 18:49, Cédric Le Goater wrote:
> On 5/30/23 18:40, Cédric Le Goater wrote:
> > On 5/30/23 18:11, Frederic Barrat wrote:
> > > The Thread Interrupt Management Area (TIMA) can be accessed through 4
> > > ports/snoop buses, targeted by the address. The base address of a TIMA
> > > is using port 0 and the other ports are 0x80 apart. Using one port or
> > > another can be useful to balance the load on the snoop buses.
> >
> > and can we have some nice examples of how these ports are used ? only for
> > snooping or also for balancing operations ? which ones ?
> >
> > > The TIMA registers are in the 0x0 -> 0x3F range and there are 2
> > > indication bits for special operations (bits 10 and 11; everything
> > > fits on a 4k page). So the port address bits fall in between and are
> > > "don't care" for the hardware when processing the TIMA operation. So
> > > this patch filters out those port address bits so that a TIMA
> > > operation can be triggered using any port.
> > >
> > > It is also true for indirect access (through the IC BAR) and it's
> > > actually nothing new, it was already the case on P9. Which helps here,
> > > as the TIMA handling code is common between P9 (xive) and P10 (xive2).
> > >
> > > Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
> >
> > Reviewed-by: Cédric Le Goater <clg@kaod.org>
>
> one extra comment, since we already have one mask for the tima offsets :
>
>      /*
>       * First, check for special operations in the 2K region
>       */
>      if (offset & 0x800) {
>
> I think it would be cleaner to add some defines in the reg definition file.


Yeah, you're right, I should respin it with some proper defines. And 
I'll add one for the special op bit(s).

  Fred


> Can come later.
>
> Thanks,
>
> C.