[PATCH v2] perf/arm-cmn: Fix DTC reset

[Robin Murphy]

It turns out that my naive DTC reset logic fails to work as intended,
since, after checking with the hardware designers, the PMU actually
needs to be fully enabled in order to correctly clear any pending
overflows. Therefore, invert the sequence to start with turning on both
enables so that we can reliably get the DTCs into a known state, then
moving to our normal counters-stopped state from there. Since all the
DTM counters have already been unpaired during the initial discovery
pass, we just need to additionally reset the cycle counters to ensure
that no other unexpected overflows occur during this period.

Fixes: 0ba64770a2f2 ("perf: Add Arm CMN-600 PMU driver")
Reported-by: Geoff Blake <blakgeof at amazon.com>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---

v2: Changed just about everything

 drivers/perf/arm-cmn.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index b57a0472ea0d..cd2648980540 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1899,9 +1899,10 @@ static int arm_cmn_init_dtc(struct arm_cmn *cmn, struct arm_cmn_node *dn, int id
 	if (dtc->irq < 0)
 		return dtc->irq;
 
-	writel_relaxed(0, dtc->base + CMN_DT_PMCR);
+	writel_relaxed(CMN_DT_DTC_CTL_DT_EN, dtc->base + CMN_DT_DTC_CTL);
+	writel_relaxed(CMN_DT_PMCR_PMU_EN | CMN_DT_PMCR_OVFL_INTR_EN, dtc->base + CMN_DT_PMCR);
+	writeq_relaxed(0, dtc->base + CMN_DT_PMCCNTR);
 	writel_relaxed(0x1ff, dtc->base + CMN_DT_PMOVSR_CLR);
-	writel_relaxed(CMN_DT_PMCR_OVFL_INTR_EN, dtc->base + CMN_DT_PMCR);
 
 	return 0;
 }
@@ -1961,7 +1962,7 @@ static int arm_cmn_init_dtcs(struct arm_cmn *cmn)
 			dn->type = CMN_TYPE_CCLA;
 	}
 
-	writel_relaxed(CMN_DT_DTC_CTL_DT_EN, cmn->dtc[0].base + CMN_DT_DTC_CTL);
+	arm_cmn_set_state(cmn, CMN_STATE_DISABLED);
 
 	return 0;
 }
-- 
2.39.2.101.g768bb238c484.dirty