Re: [PATCH] arm64: dts: qcom: shikra: Switch CPU ETMs to MMIO-based probing

[Jie Gan]

On 10/14/2026 4:31 PM, Konrad Dybcio wrote:
> On 10/14/26 10:19 AM, Jie Gan wrote:
> > On 10/13/2026 8:38 PM, Konrad Dybcio wrote:
> > > On 9/22/26 5:09 AM, Jie Gan wrote:
> > > > The etm0-etm3 nodes are declared with "arm,coresight-etm4x-sysreg"
> > > > but do not implement self-hosted system-register trace access on
> > > > this SoC: ID_AA64DFR0_EL1.TraceVer reads as 0 on the affected CPUs,
> > > > so etm4_init_sysreg_access() correctly reports the access mechanism
> > > > as unavailable and the ETMv4 driver fails to probe with -EINVAL.
> > > >
> > > > The CPU ETMs have a memory-mapped aperture, so switch each node to
> > > > the standard "arm,coresight-etm4x", "arm,primecell" compatible with
> > > > its MMIO reg range.
> > > >
> > > > Fixes: eed738c6dd0c ("arm64: dts: qcom: shikra: Add coresight nodes")
> > > > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > > > ---
> > >
> > > Do we still need qcom,skip-power-up on new SoCs *with* MMIO access?
> >
> > Yes, we need qcom,skip-power-up for all ETM device with or w/o MMIO access.
> >
> > > GPT has concerns regarding whether we need to add
> > > arm,coresight-loses-context-with-cpu>
> >
> > This logic to be handled by HYP on Shikra SoC, so I didnt enable it in kernel.
>
> https://lore.kernel.org/linux-arm-msm/20261005-shikra-el2-v3-0-618f7343695c@xxxxxxxxxxxxxxxx/
>
> We're going to, in parallel, ship Shikra without the Qualcomm
> hypervisor so please keep that in mind. Should the submitters of the
> non-Gunyah overlay add these properties there as they respin? Does
> that concern all Coresight components?

Making sense.

I will add the property.

Thanks,
Jie

> Konrad