[PATCH 28/28] coresight: etm4x: adding configurable start/stop filtering

[Mathieu Poirier]

With this patch we add start/stop filtering as specified on
the perf cmd line.  When the IP matches the start address
trace generation gets triggered.  The stop condition is
achieved when the IP matches the stop address.

Signed-off-by: Mathieu Poirier <mathieu.poirier at linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 71 +++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index ebaefb45130f..4db8d6a4d0cb 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -335,12 +335,25 @@ static void etm4_disable_hw(void *info)
 static int etm4_disable_perf(struct coresight_device *csdev,
 			     struct perf_event *event)
 {
+	u32 control;
+	struct etm_filters *filters = event->hw.addr_filters;
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
 	if (WARN_ON_ONCE(drvdata->cpu != smp_processor_id()))
 		return -EINVAL;
 
 	etm4_disable_hw(drvdata);
+
+	/*
+	 * Check if the start/stop logic was active when the unit was stopped.
+	 * That way we can re-enable the start/stop logic when the process is
+	 * scheduled again.  Configuration of the start/stop logic happens in
+	 * function etm4_set_event_filters().
+	 */
+	control = readl_relaxed(drvdata->base + TRCVICTLR);
+	/* TRCVICTLR::SSSTATUS, bit[9] */
+	filters->ssstatus = (control & BIT(9));
+
 	return 0;
 }
 
@@ -657,6 +670,27 @@ static void etm4_set_comparator_filter(struct etmv4_config *config,
 	config->viiectlr |= BIT(comparator / 2);
 }
 
+static void etm4_set_start_stop_filter(struct etmv4_config *config,
+				       u64 address, int comparator,
+				       enum etm_addr_type type)
+{
+	int shift;
+	u64 access_type = etm4_get_access_type(config);
+
+	/* Configure the comparator */
+	config->addr_val[comparator] = address;
+	config->addr_acc[comparator] = access_type;
+	config->addr_type[comparator] = type;
+
+	/*
+	 * Configure ViewInst Start-Stop control register.
+	 * Addresses configured to start tracing go from bit 0 to n-1,
+	 * while those configured to stop tracing from 16 to 16 + n-1.
+	 */
+	shift = (type == ETM_ADDR_TYPE_START ? 0 : 16);
+	config->vissctlr |= BIT(shift + comparator);
+}
+
 static void etm4_set_default_filter(struct etmv4_config *config)
 {
 	u64 start, stop;
@@ -721,6 +755,14 @@ static int etm4_get_next_comparator(struct etmv4_drvdata *drvdata, u32 type)
 			/* Address range comparators go in pairs */
 			index += 2;
 			break;
+		case ETM_ADDR_TYPE_START:
+		case ETM_ADDR_TYPE_STOP:
+			if (config->addr_type[index] == ETM_ADDR_TYPE_NONE)
+				return index;
+
+			/* Start/stop address can have odd indexes */
+			index += 1;
+			break;
 		default:
 			return -EINVAL;
 		}
@@ -734,6 +776,7 @@ static int etm4_set_event_filters(struct etmv4_drvdata *drvdata,
 				  struct perf_event *event)
 {
 	int i, comparator, ret = 0;
+	u64 address;
 	struct etmv4_config *config = &drvdata->config;
 	struct etm_filters *filters = event->hw.addr_filters;
 
@@ -776,6 +819,34 @@ static int etm4_set_event_filters(struct etmv4_drvdata *drvdata,
 			/* No start-stop filtering for ViewInst */
 			config->vissctlr = 0x0;
 			break;
+		case ETM_ADDR_TYPE_START:
+		case ETM_ADDR_TYPE_STOP:
+			/* Get the right start or stop address */
+			address = (type == ETM_ADDR_TYPE_START ?
+				   filter->start_addr :
+				   filter->stop_addr);
+
+			/* Configure comparator */
+			etm4_set_start_stop_filter(config, address,
+						   comparator, type);
+
+			/*
+			 * If filters::ssstatus == 1, trace acquisition was
+			 * started but the process was yanked away before the
+			 * the stop address was hit.  As such the start/stop
+			 * logic needs to be re-started so that tracing can
+			 * resume where it left.
+			 *
+			 * The start/stop logic status when a process is
+			 * scheduled out is checked in function
+			 * etm4_disable_perf().
+			 */
+			if (filters->ssstatus)
+				config->vinst_ctrl |= BIT(9);
+
+			/* No include/exclude filtering for ViewInst */
+			config->viiectlr = 0x0;
+			break;
 		default:
 			ret = -EINVAL;
 			goto out;
-- 
2.7.4