linux-kernel - Re: [PATCH] arm64: dts: qcom: qcs615: fix a crash issue caused by infinite loop for Coresight

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Message-ID: <CAJ9a7Vg7MtLaud715JYEo5JD6x4WmHq9TsSSor1-TYq5M5u+cw@mail.gmail.com>
Date: Wed, 28 May 2025 14:30:58 +0100
From: Mike Leach <mike.leach@...aro.org>
To: Jie Gan <jie.gan@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Suzuki K Poulose <suzuki.poulose@....com>, James Clark <james.clark@...aro.org>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: qcs615: fix a crash issue caused by
 infinite loop for Coresight

Hi,

This is clearly a platform issue - loops as you describe are not
permitted by the CoreSight architecture specification.

We should not be trying to fix issues that are out of specification in
the drivers.

Regards

Mike

On Mon, 26 May 2025 at 01:40, Jie Gan <jie.gan@....qualcomm.com> wrote:
>
>
>
> On 5/22/2025 11:06 PM, Konrad Dybcio wrote:
> > On 5/22/25 2:50 AM, Jie Gan wrote:
> >> An infinite loop has been created by the Coresight devices. When only a
> >> source device is enabled, the coresight_find_activated_sysfs_sink function
> >> is recursively invoked in an attempt to locate an active sink device,
> >> ultimately leading to a stack overflow and system crash. Therefore, disable
> >> the replicator1 to break the infinite loop and prevent a potential stack
> >> overflow.
> >
> > Is it something we can fix the driver not to do instead?
> >
>
> As Suzuki mentioned in other mail thread, it is very difficult to
> observe the scenario that there is a loop in the path by current driver.
>
> I tried fix the issue in driver before send this DT fix patch.
> I will continue to seek an option of fixing in driver.
>
> Thanks,
> Jie
>
> > Konrad
> >
> >>
> >> replicator1_out   ->   funnel_swao_in6   ->   tmc_etf_swao_in   ->  tmc_etf_swao_out
> >>       |                                                                     |
> >> replicator1_in                                                     replicator_swao_in
> >>       |                                                                     |
> >> replicator0_out1                                                   replicator_swao_out0
> >>       |                                                                     |
> >> replicator0_in                                                     funnel_in1_in3
> >>       |                                                                     |
> >> tmc_etf_out <- tmc_etf_in <- funnel_merg_out <- funnel_merg_in1 <- funnel_in1_out
> >>
> >> [call trace]
> >>     dump_backtrace+0x9c/0x128
> >>     show_stack+0x20/0x38
> >>     dump_stack_lvl+0x48/0x60
> >>     dump_stack+0x18/0x28
> >>     panic+0x340/0x3b0
> >>     nmi_panic+0x94/0xa0
> >>     panic_bad_stack+0x114/0x138
> >>     handle_bad_stack+0x34/0xb8
> >>     __bad_stack+0x78/0x80
> >>     coresight_find_activated_sysfs_sink+0x28/0xa0 [coresight]
> >>     coresight_find_activated_sysfs_sink+0x5c/0xa0 [coresight]
> >>     coresight_find_activated_sysfs_sink+0x5c/0xa0 [coresight]
> >>     coresight_find_activated_sysfs_sink+0x5c/0xa0 [coresight]
> >>     coresight_find_activated_sysfs_sink+0x5c/0xa0 [coresight]
> >>     ...
> >>     coresight_find_activated_sysfs_sink+0x5c/0xa0 [coresight]
> >>     coresight_enable_sysfs+0x80/0x2a0 [coresight]
> >>
> >> side effect after the change:
> >> Only trace data originating from AOSS can reach the ETF_SWAO and EUD sinks.
> >>
> >> Fixes: bf469630552a ("arm64: dts: qcom: qcs615: Add coresight nodes")
> >> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
> >> ---
> >>   arch/arm64/boot/dts/qcom/qcs615.dtsi | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/qcs615.dtsi b/arch/arm64/boot/dts/qcom/qcs615.dtsi
> >> index f08ba09772f3..b67c1f8a1118 100644
> >> --- a/arch/arm64/boot/dts/qcom/qcs615.dtsi
> >> +++ b/arch/arm64/boot/dts/qcom/qcs615.dtsi
> >> @@ -1902,6 +1902,7 @@ replicator@...a000 {
> >>
> >>                      clocks = <&aoss_qmp>;
> >>                      clock-names = "apb_pclk";
> >> +                    status = "disabled";
> >>
> >>                      in-ports {
> >>                              port {
>


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