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

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Message-ID: <2f010e28-121e-4e60-bf48-5ee5bcd0cbea@oss.qualcomm.com>
Date: Mon, 26 May 2025 08:40:46 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: 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>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>
Cc: 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



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 {