On Mon, Jan 16, 2017 at 06:00:00PM +0000, Suzuki K Poulose wrote:
> The stm is automatically enabled when an application sets the policy
> via ->link() call back by using coresight_enable(), which keeps the
> refcount of the current users of the STM. However, the unlink() callback
> issues stm_disable() directly, which leaves the STM turned off, without
> the coresight layer knowing about it. This prevents any further uses
> of the STM hardware as the coresight layer still thinks the STM is
> turned on and doesn't enable the hardware when required. Even manually
> enabling the STM via sysfs can't really enable the hw.
>
> e.g,
>
> $ echo 1 > $CS_DEVS/$ETR/enable_sink
> $ mkdir -p $CONFIG_FS/stp-policy/$source.0/stm_test/
> $ echo 32768 65535 > $CONFIG_FS/stp-policy/$source.0/stm_test/channels
> $ echo 64 > $CS_DEVS/$source/traceid
> $ ./stm_app
> Sending 64000 byte blocks of pattern 0 at 0us intervals
> Success to map channel(32768~32783) to 0xffffa95fa000
> Sending on channel 32768
> $ dd if=/dev/$ETR of=~/trace.bin.1
> 597+1 records in
> 597+1 records out
> 305920 bytes (306 kB) copied, 0.399952 s, 765 kB/s
> $ ./stm_app
> Sending 64000 byte blocks of pattern 0 at 0us intervals
> Success to map channel(32768~32783) to 0xffff7e9e2000
> Sending on channel 32768
> $ dd if=/dev/$ETR of=~/trace.bin.2
> 0+0 records in
> 0+0 records out
> 0 bytes (0 B) copied, 0.0232083 s, 0.0 kB/s
>
> Note that we don't get any data from the ETR for the second session.
>
> Also dmesg shows :
>
> [ 77.520458] coresight-tmc 20800000.etr: TMC-ETR enabled
> [ 77.537097] coresight-replicator etr_replicator@20890000: REPLICATOR enabled
> [ 77.558828] coresight-replicator main_replicator@208a0000: REPLICATOR enabled
> [ 77.581068] coresight-funnel 208c0000.main_funnel: FUNNEL inport 0 enabled
> [ 77.602217] coresight-tmc 20840000.etf: TMC-ETF enabled
> [ 77.618422] coresight-stm 20860000.stm: STM tracing enabled
> [ 139.554252] coresight-stm 20860000.stm: STM tracing disabled
> # End of first tracing session
> [ 146.351135] coresight-tmc 20800000.etr: TMC read start
> [ 146.514486] coresight-tmc 20800000.etr: TMC read end
> # Note that the STM is not turned on via stm_generic_link()->coresight_enable()
> # and hence none of the components are turned on.
> [ 152.479080] coresight-tmc 20800000.etr: TMC read start
> [ 152.542632] coresight-tmc 20800000.etr: TMC read end
>
> This patch fixes the problem by balancing the unlink operation by using
> the coresight_disable(), keeping the coresight layer in sync with the
> hardware state and thus allowing normal usage of the STM component.
>
> Fixes: commit 237483aa5cf43 ("coresight: stm: adding driver for CoreSight STM component")
> Cc: Pratik Patel <pratikp@xxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # 4.7+
> Acked-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Reviewed-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
> Reported-by: Robert Walker <robert.walker@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>
> Greg,
>
> Without this patch, the coresight STM IP can only be used for one tracing
> session per boot, seriously limiting its usability.
When you resend a patch, please tell me what is different from the
previous version you sent. I figured it out here, but please do this
next time.
thanks,
greg k-h
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