On 30 September 2015 at 05:33, Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> wrote: > Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> 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@xxxxxxxxxx> >> --- >> 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. >> */ >> etm_clr_pwrdwn(drvdata); >> + >> + /* 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. > That's > why smp_function_call() was needed there. Or you might want a > etm_read_on_cpu() variant if it's really worth it. > >> + drvdata->os_unlock = true; >> + >> /* >> * Set prog bit. It will be set from reset but this is included to >> * ensure it is set >> @@ -1961,9 +1966,6 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id) >> get_online_cpus(); >> etmdrvdata[drvdata->cpu] = drvdata; >> >> - if (!smp_call_function_single(drvdata->cpu, etm_os_unlock, drvdata, 1)) >> - drvdata->os_unlock = true; >> - >> if (smp_call_function_single(drvdata->cpu, >> etm_init_arch_data, drvdata, 1)) >> dev_err(dev, "ETM arch init failed\n"); >> -- >> 1.9.1 > > Regards, > -- > Alex -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
