From: Joakim Zhang <qiangqing.zhang@xxxxxxx>
[ Upstream commit 049d919168458ac54e7fad27cd156a958b042d2f ]
When disabling a counter from ddr_perf_event_stop(), the counter value
is reset to 0 at the same time.
Preserve the counter value by performing a read-modify-write of the
PMU register and clearing only the enable bit.
Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/perf/fsl_imx8_ddr_perf.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
index 0e51baa48b149..6eef47de8fccc 100644
--- a/drivers/perf/fsl_imx8_ddr_perf.c
+++ b/drivers/perf/fsl_imx8_ddr_perf.c
@@ -327,9 +327,10 @@ static void ddr_perf_counter_enable(struct ddr_pmu *pmu, int config,
if (enable) {
/*
- * must disable first, then enable again
- * otherwise, cycle counter will not work
- * if previous state is enabled.
+ * cycle counter is special which should firstly write 0 then
+ * write 1 into CLEAR bit to clear it. Other counters only
+ * need write 0 into CLEAR bit and it turns out to be 1 by
+ * hardware. Below enable flow is harmless for all counters.
*/
writel(0, pmu->base + reg);
val = CNTL_EN | CNTL_CLEAR;
@@ -337,7 +338,8 @@ static void ddr_perf_counter_enable(struct ddr_pmu *pmu, int config,
writel(val, pmu->base + reg);
} else {
/* Disable counter */
- writel(0, pmu->base + reg);
+ val = readl_relaxed(pmu->base + reg) & CNTL_EN_MASK;
+ writel(val, pmu->base + reg);
}
}
--
2.20.1
