Re: [RESEND PATCH v3 1/2] drivers: amba: Updates to component identification for driver matching.

[Suzuki K Poulose]

Mike,

On 25/01/2019 10:37, Mike Leach wrote:
> Hello Sai
> On Fri, 25 Jan 2019 at 07:20, Sai Prakash Ranjan
> <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
> > Hi Mike,
> >
> > Thanks for the patch.
> >
> > BTW somehow I can't find the latest series in my inbox, so commenting
> > on this here.
> >
> > Mathieu pointed me to this patch series.This solves CPU debug module
> > sharing same PID as ETM on MSM8996. I will be posting patch for CPU
> > debug UCI table soon.
> >
> > But please find my one comment inline.
> >
> > On 12/19/2018 3:29 AM, Mike Leach wrote:
> > > The CoreSight specification (ARM IHI 0029E), updates the ID register
> > > requirements for components on an AMBA bus, to cover both traditional
> > > ARM Primecell type devices, and newer CoreSight and other components.
> > >
> > > The Peripheral ID (PID) / Component ID (CID) pair is extended in certain
> > > cases to uniquely identify components. CoreSight components related to
> > > a single function can share Peripheral ID values, and must be further
> > > identified using a Unique Component Identifier (UCI). e.g. the ETM, CTI,
> > > PMU and Debug hardware of the A35 all share the same PID.
> >
> > [..]
> >
> > > +static const struct amba_id *
> > > +amba_lookup(const struct amba_id *table, struct amba_device *dev)
> > > +{
> > >        while (table->mask) {
> > > -             ret = (dev->periphid & table->mask) == table->id;
> > > -             if (ret)
> > > -                     break;
> > > +             if (((dev->periphid & table->mask) == table->id) &&
> > > +                     ((dev->cid != CORESIGHT_CID) ||
> > > +                      (amba_cs_uci_id_match(table, dev))))
> >
> > Shouldn't the check be (dev->cid == CORESIGHT_CID) ?
> > Without this STM fails to probe on both SDM845 and MSM8996.
> I believe the test is correct
>
> To expand the logic here:
>
> if  (dev->periphid & table->mask) == table->id) {
>        //** match on peripheral ID at this point
>       if (CID != CORESIGHT_ID)
>                 return table; //** not coresight - match on peripheral ID only
>       //** or
>       if (amba_cs_uci_id_match() )
>                  return table;  //** is coresight - match on UCI if
> available - otherwise peripheral ID only;
>
> However - looking at the coresight STM driver - this is using the
> private .data field in the amba_id for a name - which I had not
> spotted before.

Good point. We also use this field for Coresight SOC-600 ETR for
advertising the caps not detected from hardware.

> I will have to revisit this patchset to fix either the amba id struct
> or the method for getting the uci data into the amba_id.data which
> allows for multiple uses.

Thanks Mike !

Cheers
Suzuki