perf/arm-cmn: Fix DTC reset

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@amazon.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/0ea4559261ea394f827c9aee5168c77a60aaee03.1684946389.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 47d359f729579b64d2a937b203ec52f12020880a..89a685a09d848fc868647e655d2d059a0587df48 100644 (file)
--- 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;
 }