From mboxrd@z Thu Jan 1 00:00:00 1970 From: suzuki.poulose@arm.com (Suzuki K Poulose) Date: Thu, 8 Nov 2018 09:49:28 +0000 Subject: [PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf In-Reply-To: <20181107032350.GH3983@leoy-ThinkPad-X240s> References: <1541456790-28282-1-git-send-email-mathieu.poirier@linaro.org> <1541456790-28282-4-git-send-email-mathieu.poirier@linaro.org> <20181107032350.GH3983@leoy-ThinkPad-X240s> Message-ID: <054f82c1-451f-3c82-d5ab-e156c50e0c10@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Leo, On 07/11/2018 03:23, leo.yan at linaro.org 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 >> --- >> 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. Suzuki > > Thanks, > Leo Yan > >> CS_LOCK(drvdata->base); >> } >> >> -- >> 2.7.4 >>