Re: [PATCH 3/3] perf/arm-cmn: Enable per-DTC counter allocation

From: Ilkka Koskinen
Date: Fri Oct 20 2023 - 19:01:14 EST



Hi Robin,

It seems that I somehow managed to reply to patch 2/3 second time with the comments that were supposed to be here... :(

On Fri, 20 Oct 2023, Robin Murphy wrote:
Finally enable independent per-DTC-domain counter allocation, except on
CMN-600 where we still need to cope with not knowing the domain topology
and thus keep counter indices sychronised across domains. This allows
users to simultaneously count up to 8 targeted events per domain, rather
than 8 globally, for up to 4x wider coverage on maximum configurations.

Even though this now looks deceptively simple, I stand by my previous
assertion that it was a flippin' nightmare to implement; all the real
head-scratchers are hidden in the foundations in the previous patch...

Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>

Thanks! I had that on my task list but never had time to start working on
it.

Reviewed-by: Ilkka Koskinen <ilkka at os.amperecomputing.com>

Cheers, Ilkka


---
drivers/perf/arm-cmn.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 675f1638013e..9479e919c063 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1570,7 +1570,7 @@ struct arm_cmn_val {
u8 dtm_count[CMN_MAX_DTMS];
u8 occupid[CMN_MAX_DTMS][SEL_MAX];
u8 wp[CMN_MAX_DTMS][4];
- int dtc_count;
+ int dtc_count[CMN_MAX_DTCS];
bool cycles;
};

@@ -1591,7 +1591,8 @@ static void arm_cmn_val_add_event(struct arm_cmn *cmn, struct arm_cmn_val *val,
return;
}

- val->dtc_count++;
+ for_each_hw_dtc_idx(hw, dtc, idx)
+ val->dtc_count[dtc]++;

for_each_hw_dn(hw, dn, i) {
int wp_idx, dtm = dn->dtm, sel = hw->filter_sel;
@@ -1638,8 +1639,9 @@ static int arm_cmn_validate_group(struct arm_cmn *cmn, struct perf_event *event)
goto done;
}

- if (val->dtc_count == CMN_DT_NUM_COUNTERS)
- goto done;
+ for (i = 0; i < CMN_MAX_DTCS; i++)
+ if (val->dtc_count[i] == CMN_DT_NUM_COUNTERS)
+ goto done;

for_each_hw_dn(hw, dn, i) {
int wp_idx, wp_cmb, dtm = dn->dtm, sel = hw->filter_sel;
@@ -1806,9 +1808,9 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
return 0;
}

- /* Grab a free global counter first... */
+ /* Grab the global counters first... */
for_each_hw_dtc_idx(hw, j, idx) {
- if (j > 0) {
+ if (cmn->part == PART_CMN600 && j > 0) {
idx = hw->dtc_idx[0];
} else {
idx = 0;
@@ -1819,10 +1821,10 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
hw->dtc_idx[j] = idx;
}

- /* ...then the local counters to feed it. */
+ /* ...then the local counters to feed them */
for_each_hw_dn(hw, dn, i) {
struct arm_cmn_dtm *dtm = &cmn->dtms[dn->dtm] + hw->dtm_offset;
- unsigned int dtm_idx, shift, d = 0;
+ unsigned int dtm_idx, shift, d = max_t(int, dn->dtc, 0);
u64 reg;

dtm_idx = 0;
--
2.39.2.101.g768bb238c484.dirty