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

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