[PATCH v10 8/8] Documentation: coresight: Panic support

[Bagas Sanjaya]

On Mon, Sep 16, 2024 at 04:04:37PM +0530, Linu Cherian wrote:
> +3. On a kernel panic, all coresight blocks are disabled, necessary
> +   metadata is synced by kernel panic handler.
"... and necessary metadata ..."
> +
> +   System would eventually reboot or boot a crashdump kernel.
> +
> +4. For  platforms that supports crashdump kernel, raw trace data can be
> +   dumped using the coresight sysfs interface from the crashdump kernel
> +   itself. Persistent RAM is not a requirement in this case.
> +
> +5. For platforms that supports persistent RAM, trace data can be dumped
> +   using the coresight sysfs interface in the subsequent Linux boot.
> +   Crashdump kernel is not a requirement in this case. Persistent RAM
> +   ensures that trace data is intact across reboot.
> +
> +Coresight trace during Watchdog reset
> +-------------------------------------
> +The main difference between addressing the watchdog reset and kernel panic
> +case are below,
"... are:"
> +Sample commands for testing a Kernel panic case with ETR sink
> +-------------------------------------------------------------
> +
> +1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
> +   bootargs. This is mandatory if the user would like to read the tracedata
> +   from the crashdump kernel.
> +
> +2. Enable the preloaded ETM configuration
> +
> +    #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
> +
> +3. Configure CTI using sysfs interface::
> +
> +    #./cti_setup.sh
> +
> +    #cat cti_setup.sh
> +
> +
> +    cd /sys/bus/coresight/devices/
> +
> +    ap_cti_config () {
> +      #ETM trig out[0] trigger to Channel 0
> +      echo 0 4 > channels/trigin_attach
> +    }
> +
> +    etf_cti_config () {
> +      #ETF Flush in trigger from Channel 0
> +      echo 0 1 > channels/trigout_attach
> +      echo 1 > channels/trig_filter_enable
> +    }
> +
> +    etr_cti_config () {
> +      #ETR Flush in from Channel 0
> +      echo 0 1 > channels/trigout_attach
> +      echo 1 > channels/trig_filter_enable
> +    }
> +
> +    ctidevs=`find . -name "cti*"`
> +
> +    for i in $ctidevs
> +    do
> +            cd $i
> +
> +            connection=`find . -name "ete*"`
> +            if [ ! -z "$connection" ]
> +            then
> +                    echo "AP CTI config for $i"
> +                    ap_cti_config
> +            fi
> +
> +            connection=`find . -name "tmc_etf*"`
> +            if [ ! -z "$connection" ]
> +            then
> +                    echo "ETF CTI config for $i"
> +                    etf_cti_config
> +            fi
> +
> +            connection=`find . -name "tmc_etr*"`
> +            if [ ! -z "$connection" ]
> +            then
> +                    echo "ETR CTI config for $i"
> +                    etr_cti_config
> +            fi
> +
> +            cd ..
> +    done
> +
> +Note: CTI connections are SOC specific and hence the above script is
> +added just for reference.
> +
> +4. Choose reserved buffer mode for ETR buffer
> +    #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
> +
> +5. Enable stop on flush trigger configuration
> +    #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
> +
> +6. Start Coresight tracing on cores 1 and 2 using sysfs interface
> +
> +7. Run some application on core 1
> +    #taskset -c 1 dd if=/dev/urandom of=/dev/null &
> +
> +8. Invoke kernel panic on core 2
> +    #echo 1 > /proc/sys/kernel/panic
> +    #taskset -c 2 echo c > /proc/sysrq-trigger
> +
> +9. From rebooted kernel or crashdump kernel, read crashdata
> +
> +    #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
> +
> +10. Run opencsd decoder tools/scripts to generate the instruction trace.

Format all command lines as literal code blocks to be consistent:

---- >8 ----
diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
index 3b53d91cace8fd..864f6c05b3f7af 100644
--- a/Documentation/trace/coresight/panic.rst
+++ b/Documentation/trace/coresight/panic.rst
@@ -113,7 +113,7 @@ Sample commands for testing a Kernel panic case with ETR sink
    bootargs. This is mandatory if the user would like to read the tracedata
    from the crashdump kernel.
 
-2. Enable the preloaded ETM configuration
+2. Enable the preloaded ETM configuration::
 
     #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
 
@@ -176,22 +176,26 @@ Sample commands for testing a Kernel panic case with ETR sink
 Note: CTI connections are SOC specific and hence the above script is
 added just for reference.
 
-4. Choose reserved buffer mode for ETR buffer
+4. Choose reserved buffer mode for ETR buffer::
+
     #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
 
-5. Enable stop on flush trigger configuration
+5. Enable stop on flush trigger configuration::
+
     #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
 
 6. Start Coresight tracing on cores 1 and 2 using sysfs interface
 
-7. Run some application on core 1
+7. Run some application on core 1::
+
     #taskset -c 1 dd if=/dev/urandom of=/dev/null &
 
-8. Invoke kernel panic on core 2
+8. Invoke kernel panic on core 2::
+
     #echo 1 > /proc/sys/kernel/panic
     #taskset -c 2 echo c > /proc/sysrq-trigger
 
-9. From rebooted kernel or crashdump kernel, read crashdata
+9. From rebooted kernel or crashdump kernel, read crashdata::
 
     #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
 
Thanks.

-- 
An old man doll... just what I always wanted! - Clara
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