[PATCH 1/3] perf/imx_ddr: speed up overflow frequency of cycle counter

[Xu Yang]

For i.MX8MP, we cannot ensure that cycle counter overflow occurs at least
4 times as often as other events. Due to byte counters will count for any
event configured, it will overflow more often. And if byte counters
overflow that related counters would stop since they share the COUNTER_CNTL.
We can speed up cycle counter overflow frequency by setting counter parameter
(CP) field of cycle counter. In this way, we can avoid stop counting byte
counters when interrupt didn't come and the byte counters can be fetched or
updated from each cycle counter overflow interrupt.

Signed-off-by: Xu Yang <xu.yang_2 at nxp.com>
---
 drivers/perf/fsl_imx8_ddr_perf.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
index 5222ba1e79d0..cc7693f49950 100644
--- a/drivers/perf/fsl_imx8_ddr_perf.c
+++ b/drivers/perf/fsl_imx8_ddr_perf.c
@@ -28,6 +28,8 @@
 #define CNTL_CLEAR_MASK		0xFFFFFFFD
 #define CNTL_OVER_MASK		0xFFFFFFFE
 
+#define CNTL_CP_SHIFT		16
+#define CNTL_CP_MASK		(0xFF << CNTL_CP_SHIFT)
 #define CNTL_CSV_SHIFT		24
 #define CNTL_CSV_MASK		(0xFFU << CNTL_CSV_SHIFT)
 
@@ -427,6 +429,20 @@ static void ddr_perf_counter_enable(struct ddr_pmu *pmu, int config,
 		writel(0, pmu->base + reg);
 		val = CNTL_EN | CNTL_CLEAR;
 		val |= FIELD_PREP(CNTL_CSV_MASK, config);
+
+		/*
+		 * Workaround for i.MX8MP:
+		 * Common counters and byte counters share the same COUNTER_CNTL,
+		 * and byte counters could overflow before cycle counter. Need set
+		 * counter parameter(CP) of cycle counter to give it initial value
+		 * which can speed up cycle counter overflow frequency.
+		 */
+		if ((pmu->devtype_data->quirks & DDR_CAP_AXI_ID_FILTER_ENHANCED) ==
+		    DDR_CAP_AXI_ID_FILTER_ENHANCED) {
+			if (counter == EVENT_CYCLES_COUNTER)
+				val |= FIELD_PREP(CNTL_CP_MASK, 0xf0);
+		}
+
 		writel(val, pmu->base + reg);
 	} else {
 		/* Disable counter */
-- 
2.34.1