From mboxrd@z Thu Jan 1 00:00:00 1970 From: kim.phillips@arm.com (Kim Phillips) Date: Wed, 14 Jun 2017 22:34:53 -0500 Subject: [PATCH 00/17] coresight: next v4.12-rc4 In-Reply-To: <20170614062229.GA28496@leoy-ThinkPad-T440> References: <1496693718-9191-1-git-send-email-mathieu.poirier@linaro.org> <20170609175339.28d1d4d5a6c91a9e16c16bf7@arm.com> <20170613161712.f1f3cac734939d8728c7ed77@arm.com> <20170614062229.GA28496@leoy-ThinkPad-T440> Message-ID: <20170614223453.3357117a7f25ee68924a071c@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 14 Jun 2017 14:22:29 +0800 Leo Yan wrote: > Hi Kim, > > On Tue, Jun 13, 2017 at 04:17:12PM -0500, Kim Phillips wrote: > > [...] > > > > > Also, do the current juno platforms not have CPU debug modules? I'd > > > > like to test the new driver. > > > > > > By all means - Leo pointed out the patch adding the CPU debug entries in > > > the DT file for Juno. > > > > Thanks, I applied it, was able to > > toggle /sys/kernel/debug/coresight_cpu_debug/enable, but wasn't sure > > how to trigger the cpu debug output... > > You could trigger panic flow with command, then can see CPU debug output: > echo c > /proc/sysrq-trigger That worked, thanks. The coresight CPU debug documentation states: > At the runtime you can disable idle states with below methods: > > Set latency request to /dev/cpu_dma_latency to disable all CPUs specific idle > states (if latency = 0uS then disable all idle states): > # echo "what_ever_latency_you_need_in_uS" > /dev/cpu_dma_latency > > Disable specific CPU's specific idle state: > # echo 1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$state/disable So I tried two values in /dev/cpu_dma_latency and expected a difference in the per-cpu latency files, but didn't observe it: root at juno:~# echo 0 > /dev/cpu_dma_latency root at juno:~# more /sys/devices/system/cpu/cpu2/cpuidle*/state*/*laten* :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state0/latency :::::::::::::: 1 :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state1/latency :::::::::::::: 1500 :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state2/latency :::::::::::::: 1600 root at juno:~# echo 1500 > /dev/cpu_dma_latency root at juno:~# more /sys/devices/system/cpu/cpu2/cpuidle*/state*/*laten* :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state0/latency :::::::::::::: 1 :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state1/latency :::::::::::::: 1500 :::::::::::::: /sys/devices/system/cpu/cpu2/cpuidle/state2/latency :::::::::::::: 1600 root at juno:~# cat /sys/kernel/debug/coresight_cpu_debug/enable 1 How does one tell whether writes to /dev/cpu_dma_latency are effective? Thanks, Kim