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

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Date:   Fri, 25 Jan 2019 10:37:45 +0000
From:   Mike Leach <mike.leach@...aro.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     linux@...linux.org.uk,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        coresight@...ts.linaro.org, linux-kernel@...r.kernel.org,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>
Subject: Re: [RESEND PATCH v3 1/2] drivers: amba: Updates to component
 identification for driver matching.

Hello Sai
On Fri, 25 Jan 2019 at 07:20, Sai Prakash Ranjan
<saiprakash.ranjan@...eaurora.org> 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.
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.

Regards

Mike


> With this,
>
> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>
> Thanks,
> Sai
>
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation



-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK