trace/coresight/panic.rst

2 Using Coresight for Kernel panic and Watchdog reset
6 ------------
7 This documentation is about using Linux coresight trace support to
10 Coresight trace during Kernel panic
11 -----------------------------------
12 From the coresight driver point of view, addressing the kernel panic
17    relevant coresight nodes.
19 b. Support for stopping coresight blocks at the time of panic
27 A new optional device tree property "memory-region" is added to the
28 Coresight TMC device nodes, that would give the base address and size of trace
43 Disabling coresight blocks at the time of panic
46 kernel panic, it would be desirable to stop the coresight blocks at the
49 This can be achieved by configuring the comparator, CTI and sink
53     Comparator --->External out --->CTI -->External In---->ETR/ETF stop
57 Coresight metadata involves all additional data that are required for a
61 A new optional device property "memory-region" is added to
78 3. On a kernel panic, all coresight blocks are disabled, necessary
84    dumped using the coresight sysfs interface from the crashdump kernel
88    using the coresight sysfs interface in the subsequent Linux boot.
92 Coresight trace during Watchdog reset
93 -------------------------------------
97 a. Saving coresight metadata need to be taken care by the
110 -------------------------------------------------------------
118     #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
120 3. Configure CTI using sysfs interface::
127     cd /sys/bus/coresight/devices/
146     ctidevs=`find . -name "cti*"`
152             connection=`find . -name "ete*"`
153             if [ ! -z "$connection" ]
155                     echo "AP CTI config for $i"
159             connection=`find . -name "tmc_etf*"`
160             if [ ! -z "$connection" ]
162                     echo "ETF CTI config for $i"
166             connection=`find . -name "tmc_etr*"`
167             if [ ! -z "$connection" ]
169                     echo "ETR CTI config for $i"
176 Note: CTI connections are SOC specific and hence the above script is
181     #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
185     #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
187 6. Start Coresight tracing on cores 1 and 2 using sysfs interface
191     #taskset -c 1 dd if=/dev/urandom of=/dev/null &
196     #taskset -c 2 echo c > /proc/sysrq-trigger
224     a9be7bfd   stp     x29, x30, [sp, #-32]!
255     b85fc063   ldur    w3, [x3, #-4]
283     a9be7bfd   stp     x29, x30, [sp, #-32]!
346 ------------------
352     perf record -e cs_etm/panicstop,@tmc_etf1/ -C 1
353     perf record -e cs_etm/panicstop,@tmc_etf2/ -C 2
357     perf record -e cs_etm/panicstop,@tmc_etr0/ -C 1,2