Re: [PATCH 1/3] arm64: dts: qcom: sdm845: Add Coresight support

[Mathieu Poirier]

On Sat, Jan 12, 2019 at 06:21:00PM +0530, saiprakash.ranjan@xxxxxxxxxxxxxx wrote:
> Hi Mathieu,
> 
> > > +
> > > +	etm@7040000 {
> > > +		compatible = "arm,coresight-etm4x", "arm,primecell";
> > > +		arm,primecell-periphid = <0x000bb95d>;
> > 
> > I'm a little curious as to why you need to bypass the normal AMBA bus
> > discovery
> > method by forcing the peripheral ID.  Tracers don't show up the way
> > other
> > coresight devices do at boot time?
> > 
> 
> Yes on some Qcom SoC's like SDM845 and also on some previous ones, for
> ETM(only) amba bus discovery method fails because of wrong pid read from the
> registers. So we have to force this primecell peripheral ids to probe etm.

Ok, if that is the case please add a comment to explain the situation.
Otherwise someone will assuredly ask again in the future.

Mathieu


> 
> - Sai
> 
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