Re: [PATCH] arm64: dts: qcom: qcs615: disable the CTI device of the camera block

[Jie Gan]

On 6/10/2025 9:24 PM, Konrad Dybcio wrote:
> On 6/3/25 5:17 AM, Jie Gan wrote:
> > On 5/31/2025 7:05 AM, Konrad Dybcio wrote:
> > > On 5/28/25 5:02 AM, Jie Gan wrote:
> > > > On 5/27/2025 6:41 PM, Konrad Dybcio wrote:
> > > > > On 5/27/25 12:32 PM, Jie Gan wrote:
> > > > > > On 5/27/2025 6:23 PM, Konrad Dybcio wrote:
> > > > > > > On 5/27/25 3:52 AM, Jie Gan wrote:
> > > > > > > > Disable the CTI device of the camera block to prevent potential NoC errors
> > > > > > > > during AMBA bus device matching.
> > > > > > > >
> > > > > > > > The clocks for the Qualcomm Debug Subsystem (QDSS) are managed by aoss_qmp
> > > > > > > > through a mailbox. However, the camera block resides outside the AP domain,
> > > > > > > > meaning its QDSS clock cannot be controlled via aoss_qmp.
> > > > > > >
> > > > > > > Which clock drives it then?
> > > > > >
> > > > > > It's qcom,aoss-qmp.
> > > > > >
> > > > > > clk_prepare->qmp_qdss_clk_prepare
> > > > > > https://elixir.bootlin.com/linux/v6.15-rc7/source/drivers/soc/qcom/qcom_aoss.c#L280
> > > > >
> > > > > I'm confused about this part:
> > > > >
> > > > > > However, the camera block resides outside the AP domain,
> > > > > > meaning its QDSS clock cannot be controlled via aoss_qmp.
> > > > >
> > > > > Do we need to poke the QMP of another DRV?
> > > >
> > > > The AOSS has a clock control register for all QDSS clocks. when we vote the qdss clock, the aoss_qmp driver will send a message to AOSS to enable the clock control register, then the clock control register will enable all QDSS clocks.
> > > >
> > > > The QDSS clock is not a single clock source, it is a term that representing all the clock sources utilized by the QDSS.
> > >
> > > What I'm trying to ask is, is there any way we could enable that
> > > clock from Linux? Can the camera hw turn these on? Maybe we could
> > > trick it into enabling them?
> >
> > There is a power issue if we keep the debug clock on with a long time.
> >
> > We had a discussion with AOP to check if possible to add the debug clock of titan to the QDSS clock list, but they need time to evaluate it.
>
> Changing the firmware is a band-aid solution, as the update will never
> reach millions of devices on the market. I'm curious in whether there's
> any way (or os-accessible debug register) to manage the necessary clocks
> from Linux, as a workaround.
>
> >  From Coresight view, what we can do by now is disable it in DT to prevent the unexpected NoC error.
>
> How about something like this:

Thanks for the suggestion. It makes sense for me and much better than 
current version.

I will send a new version to fix it.

Thanks,
Jie

> diff --git a/arch/arm64/boot/dts/qcom/qcs615.dtsi b/arch/arm64/boot/dts/qcom/qcs615.dtsi
> index bb8b6c3ebd03..fc2ab750f2cd 100644
> --- a/arch/arm64/boot/dts/qcom/qcs615.dtsi
> +++ b/arch/arm64/boot/dts/qcom/qcs615.dtsi
> @@ -2461,6 +2461,9 @@ cti@6c13000 {
>   
>                          clocks = <&aoss_qmp>;
>                          clock-names = "apb_pclk";
> +
> +                       /* Not all required clocks can be enabled from the OS */
> +                       status = "fail";
>                  };
>   
>                  cti@6c20000 {
>
> Konrad