[RFC PATCH 06/20] coresight: etm3x: unlocking tracer in default arch init
mathieu.poirier at linaro.org
Fri Oct 2 10:17:15 PDT 2015
On 1 October 2015 at 22:47, Alexander Shishkin
<alexander.shishkin at linux.intel.com> wrote:
> Mathieu Poirier <mathieu.poirier at linaro.org> writes:
>> On 30 September 2015 at 05:33, Alexander Shishkin
>> <alexander.shishkin at linux.intel.com> wrote:
>>> Mathieu Poirier <mathieu.poirier at linaro.org> writes:
>>>> Calling function 'smp_call_function_single()' to unlock the
>>>> tracer and calling it right after to perform the default
>>>> initialisation doesn't make sense.
>>>> Moving 'etm_os_unlock()' just before making the default
>>>> initialisation results in the same outcome while saving
>>>> one call to 'smp_call_function_single()'.
>>>> Signed-off-by: Mathieu Poirier <mathieu.poirier at linaro.org>
>>>> drivers/hwtracing/coresight/coresight-etm3x.c | 8 +++++---
>>>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
>>>> index c6880c1ade55..a4c158df0fef 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
>>>> @@ -1867,6 +1867,11 @@ static void etm_init_arch_data(void *info)
>>>> * certain registers might be ignored.
>>>> + /* Make sure all registers are accessible */
>>>> + etm_os_unlock(drvdata);
>>> In case of co-processor register access, this will end up unlocking the
>>> local ETM instead of the one on target cpu, by the looks of it.
>> "etm_init_arch_data()" is also called from "smp_function_calls()" and
>> as such, will end up executing the correct CPU.
> Yes, but it doesn't unlock the OSLAR register, which also needs to be
> done on target cpu.
Function "etm_os_unlock()" deals with ETMOSLAR and "CS_UNLOCK()" with
ETMLAR. Both are called from "etm_init_arch_data()", which runs on
the target CPU. One thing that I will do here is move
"etm_os_unlock()" to the beginning of "etm_init_arch_data()". Other
than that I may be missing your point.
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