powerpc/perf: Freeze PMC5/6 if we're not using them

commit 7a7a41f9d5b28ac3a916b057a7d3cd3f435ee9a6 upstream.

On Power8 we can freeze PMC5 and 6 if we're not using them. Normally they
run all the time.

As noticed by Anshuman, we should unfreeze them when we disable the PMU
as there are legacy tools which expect them to run all the time.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 8 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 4a9e408644fe..362142b69d5b 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -626,6 +626,7 @@
 #define   MMCR0_TRIGGER 0x00002000UL /* TRIGGER enable */
 #define   MMCR0_PMAO    0x00000080UL /* performance monitor alert has occurred, set to 0 after handling exception */
 #define   MMCR0_SHRFC   0x00000040UL /* SHRre freeze conditions between threads */
+#define   MMCR0_FC56    0x00000010UL /* freeze counters 5 and 6 */
 #define   MMCR0_FCTI    0x00000008UL /* freeze counters in tags inactive mode */
 #define   MMCR0_FCTA    0x00000004UL /* freeze counters in tags active mode */
 #define   MMCR0_FCWAIT  0x00000002UL /* freeze counter in WAIT state */
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 1ab306815ff3..3d566ee896e2 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -75,6 +75,7 @@ static unsigned int freeze_events_kernel = MMCR0_FCS;
 
 #define MMCR0_FCHV              0
 #define MMCR0_PMCjCE            MMCR0_PMCnCE
+#define MMCR0_FC56              0
 #define MMCR0_PMAO              0
 
 #define SPRN_MMCRA              SPRN_MMCR2
@@ -870,11 +871,11 @@ static void power_pmu_disable(struct pmu *pmu)
                 }
 
                 /*
-                 * Set the 'freeze counters' bit, clear PMAO.
+                 * Set the 'freeze counters' bit, clear PMAO/FC56.
                  */
                 val  = mfspr(SPRN_MMCR0);
                 val |= MMCR0_FC;
-                val &= ~MMCR0_PMAO;
+                val &= ~(MMCR0_PMAO | MMCR0_FC56);
 
                 /*
                  * The barrier is to make sure the mtspr has been
diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
index 84cdc6d892e3..d59f5b2d4c2f 100644
--- a/arch/powerpc/perf/power8-pmu.c
+++ b/arch/powerpc/perf/power8-pmu.c
@@ -391,6 +391,10 @@ static int power8_compute_mmcr(u64 event[], int n_ev,
         if (pmc_inuse & 0x7c)
                 mmcr[0] |= MMCR0_PMCjCE;
 
+        /* If we're not using PMC 5 or 6, freeze them */
+        if (!(pmc_inuse & 0x60))
+                mmcr[0] |= MMCR0_FC56;
+
         mmcr[1] = mmcr1;
         mmcr[2] = mmcra;