On Thu, 8 Nov 2018 at 02:49, Suzuki K Poulose <[email protected]> wrote: > > Leo, > > On 07/11/2018 03:23, [email protected] wrote: > > Hi Mathieu, > > > > On Mon, Nov 05, 2018 at 03:26:30PM -0700, Mathieu Poirier wrote: > >> This patch deals with the release of the CLAIM tag when the ETM is > >> operated from perf. Otherwise the tag is left asserted and subsequent > >> requests to use the device fail. > >> > >> Signed-off-by: Mathieu Poirier <[email protected]> > >> --- > >> drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c > >> b/drivers/hwtracing/coresight/coresight-etm3x.c > >> index fd5c4cca7db5..000796394662 100644 > >> --- a/drivers/hwtracing/coresight/coresight-etm3x.c > >> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c > >> @@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device > >> *csdev) > >> */ > >> etm_set_pwrdwn(drvdata); > >> > >> + coresight_disclaim_device_unlocked(drvdata->base); > >> + > > > > > > Just remind, this isn't consistent with the sequency in function > > etm_disable_hw(), which has the reversed sequence between > > etm_set_pwrdwn() and coresight_disclaim_device_unlocked(). > > > > Not sure which one sequence is more suitable, at the first glance, > > accessing register after pwrdwn related operation might have risk for > > deadlock? > > Good point. > > I assume that the CLAIMSET/CLR registers are in the same power domain as > the LAR (Software Lock Access register) accessed below. But I will > confirm this with the architect. Based on the response, we could > streamline both the sequences.
In this case etm_set_pwrdwn() sets bit 0 of ETMCR, which disables the ETM. That being said the Embedded Trace Macrocell Architecture Specification (ID101211) mentions in section 3.5.1 that despite ETMCR bit 0 being set to 1, it is always possible to write to the claim set registers. As such I moved the release of the claim tag in function etm_disable_hw() below etm_set_pwrdwn() in the second revision of this set [1]. [1]. https://lkml.org/lkml/2018/11/8/223 > > Suzuki > > > > > Thanks, > > Leo Yan > > > >> CS_LOCK(drvdata->base); > >> } > >> > >> -- > >> 2.7.4 > >>
