Subject: Re: [RFC PATCH 1/2] core: implement OPAL_SIGNAL_SYSTEM_RESET with POWER9 scoms

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 14 Sep 2017 12:27:18 +1000

On Wed, 2017-09-13 at 23:27 +1000, Nicholas Piggin wrote:
> On Wed, 13 Sep 2017 09:18:34 +1000
> Benjamin Herrenschmidt <[email-masked]> wrote:
> 
> > On Wed, 2017-09-13 at 02:05 +1000, Nicholas Piggin wrote:
> > > This implements a way to raise system reset interrupts on other
> > > cores. This has not yet been tested on DD2 or with deeper sleep
> > > states.  
> > 
> > Reminds me, we need to workaround a bug with XSCOMs on P9
> > 
> > PSCOMs to core in the range 20010A80-20010Ab8 (list below) can fail
> > occasionally with an error of 4 (PCB_ADDRESS_ERROR). We need to
> > (silently) retry up to 32 times.
> 
> [snip]
> 
> So, just put a loop into xscom_read and xscom_write for those
> addresses for P9 chips?

Right. Well, the top bit of the address needs filtering since it's the
target core, ie, 0x20 is core 0, 0x21 is core 1 etc... to 0x37.

Cheers,
Ben.