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

["Cédric Le Goater" <clg@kaod.org>]

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.

Can come later.

Thanks,

C.