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

[Jie Gan]

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.

This property related to etm register save and restore during pm_notify.

Thanks,
Jie
> otherwise lgtm
>
> Konrad