[PATCH v4 07/10] coresight: tmc-etr: Remove sharing guards from ETR

[James Clark <james.clark@linaro.org>]

Potential sink sharing is now identified during AUX setup. Now sinks only
need to refcount and use the buffer provided by the event, which is
guaranteed to be valid and shareable.

Mismatched buffers seem very unlikely now, so remove the WARN_ON() to
reduce how much state is stored in the sink.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 39 ++-----------------------
 drivers/hwtracing/coresight/coresight-tmc.h     |  2 --
 2 files changed, 2 insertions(+), 39 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index b4b186c605c6..a2768f5bbfbc 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -36,8 +36,6 @@ struct etr_buf_hw {
  * etr_perf_buffer - Perf buffer used for ETR
  * @drvdata		- The ETR drvdaga this buffer has been allocated for.
  * @etr_buf		- Actual buffer used by the ETR
- * @pid			- The PID of the session owner that etr_perf_buffer
- *			  belongs to.
  * @snaphost		- Perf session mode
  * @nr_pages		- Number of pages in the ring buffer.
  * @pages		- Array of Pages in the ring buffer.
@@ -45,7 +43,6 @@ struct etr_buf_hw {
 struct etr_perf_buffer {
 	struct tmc_drvdata	*drvdata;
 	struct etr_buf		*etr_buf;
-	pid_t			pid;
 	bool			snapshot;
 	int			nr_pages;
 	void			**pages;
@@ -1508,7 +1505,6 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev,
 		return NULL;
 	}
 
-	etr_perf->pid = task_pid_nr(event->owner);
 	etr_perf->snapshot = snapshot;
 	etr_perf->nr_pages = nr_pages;
 	etr_perf->pages = pages;
@@ -1622,12 +1618,6 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 		goto out;
 	}
 
-	if (WARN_ON(drvdata->perf_buf != etr_buf)) {
-		lost = true;
-		raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
-		goto out;
-	}
-
 	CS_UNLOCK(drvdata->base);
 
 	tmc_flush_and_stop(drvdata);
@@ -1707,7 +1697,6 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev,
 				    struct coresight_path *path)
 {
 	int rc = 0;
-	pid_t pid;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = path->handle;
@@ -1720,35 +1709,15 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev,
 		goto unlock_out;
 	}
 
-	if (WARN_ON(!etr_perf || !etr_perf->etr_buf)) {
-		rc = -EINVAL;
-		goto unlock_out;
-	}
-
-	/* Get a handle on the pid of the session owner */
-	pid = etr_perf->pid;
-
-	/* Do not proceed if this device is associated with another session */
-	if (drvdata->pid != -1 && drvdata->pid != pid) {
-		rc = -EBUSY;
-		goto unlock_out;
-	}
-
-	/*
-	 * No HW configuration is needed if the sink is already in
-	 * use for this session.
-	 */
-	if (drvdata->pid == pid) {
+	/*  No HW configuration is needed if the sink is already in use. */
+	if (csdev->refcnt) {
 		csdev->refcnt++;
 		goto unlock_out;
 	}
 
 	rc = tmc_etr_enable_hw(drvdata, etr_perf->etr_buf);
 	if (!rc) {
-		/* Associate with monitored process. */
-		drvdata->pid = pid;
 		coresight_set_mode(csdev, CS_MODE_PERF);
-		drvdata->perf_buf = etr_perf->etr_buf;
 		csdev->refcnt++;
 	}
 
@@ -1792,11 +1761,7 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(coresight_get_mode(csdev) == CS_MODE_DISABLED);
 	tmc_etr_disable_hw(drvdata);
-	/* Dissociate from monitored process. */
-	drvdata->pid = -1;
 	coresight_set_mode(csdev, CS_MODE_DISABLED);
-	/* Reset perf specific data */
-	drvdata->perf_buf = NULL;
 
 	raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 95e5623ea881..d63fa60ecce8 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -237,7 +237,6 @@ struct tmc_resrv_buf {
  * @shared_perf_buf: CPU-wide perf buffer shared by this ETR's owner.
  * @perf_buf_mutex: Protects shared_perf_buf and its reference count.
  * @sysfs_buf:	SYSFS buffer for ETR.
- * @perf_buf:	PERF buffer for ETR.
  * @resrv_buf:  Used by ETR as hardware trace buffer and for trace data
  *		retention (after crash) only when ETR_MODE_RESRV buffer
  *		mode is enabled. Used by ETF for trace data retention
@@ -272,7 +271,6 @@ struct tmc_drvdata {
 	/* Protects shared_perf_buf and its reference count. */
 	struct mutex		perf_buf_mutex;
 	struct etr_buf		*sysfs_buf;
-	struct etr_buf		*perf_buf;
 	struct tmc_resrv_buf	resrv_buf;
 	struct tmc_resrv_buf	crash_mdata;
 };

-- 
2.43.0