[PATCH v6 07/14] gtrace: Add function to copy into perf AUX buffer

[Mayuresh Chitale]

From: Anup Patel <anup.patel@xxxxxxxxxxxxxxxx>

The RISC-V trace ramsink will need a mechanism to copy trace data
into the perf AUX buffer. Add gtrace_path_copyto_auxbuf() function
and corresponding trace driver callback copyto_auxbuf() for this
purpose.

Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxxxxxx>
Co-developed-by: Mayuresh Chitale <mayuresh.chitale@xxxxxxxxxxxxxxxx>
Signed-off-by: Mayuresh Chitale <mayuresh.chitale@xxxxxxxxxxxxxxxx>
---
 drivers/hwtracing/gtrace/gtrace-core.c | 41 ++++++++++++++++++++++++++
 include/linux/gtrace.h                 | 24 +++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/drivers/hwtracing/gtrace/gtrace-core.c b/drivers/hwtracing/gtrace/gtrace-core.c
index d7f1df90aa31..acbeb3df2135 100644
--- a/drivers/hwtracing/gtrace/gtrace-core.c
+++ b/drivers/hwtracing/gtrace/gtrace-core.c
@@ -715,6 +715,47 @@ int gtrace_path_stop(struct gtrace_path *path)
 }
 EXPORT_SYMBOL_GPL(gtrace_path_stop);
 
+int gtrace_path_copyto_auxbuf(struct gtrace_path *path,
+			      struct gtrace_perf_auxbuf *buf,
+			      size_t *bytes_copied, u64 *format)
+{
+	struct gtrace_comp_priv *sink = to_gtrace_comp_priv(gtrace_path_sink(path));
+	const struct gtrace_driver *gtdrv;
+	struct gtrace_component *comp;
+	struct gtrace_path_node *node;
+	int ret = -EOPNOTSUPP;
+	unsigned long flags;
+
+	/*
+	 * Copy only after every path using the sink has stopped; otherwise the
+	 * hardware may overwrite data being copied, or the same data may be copied
+	 * to aux buffer twice. The last path to stop does the copy. Holding the
+	 * sink's lock also stops another path from starting the sink before copy
+	 * completes.
+	 */
+	raw_spin_lock_irqsave(&sink->lock, flags);
+	if (sink->start_count) {
+		*bytes_copied = 0;
+		ret = 0;
+		goto out;
+	}
+
+	list_for_each_entry(node, &path->comp_list, head) {
+		comp = node->comp;
+		gtdrv = to_gtrace_driver(comp->dev.driver);
+		if (!gtdrv || !gtdrv->copyto_auxbuf)
+			continue;
+
+		*bytes_copied = gtdrv->copyto_auxbuf(comp, buf, format);
+		ret = 0;
+		break;
+	}
+out:
+	raw_spin_unlock_irqrestore(&sink->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gtrace_path_copyto_auxbuf);
+
 struct gtrace_path *gtrace_create_path(struct gtrace_component *source,
 				       struct gtrace_component *sink,
 				       enum gtrace_component_mode mode)
diff --git a/include/linux/gtrace.h b/include/linux/gtrace.h
index a4b99c87d250..ed0e751faa91 100644
--- a/include/linux/gtrace.h
+++ b/include/linux/gtrace.h
@@ -266,9 +266,30 @@ void gtrace_destroy_path(struct gtrace_path *path);
 int gtrace_path_start(struct gtrace_path *path);
 int gtrace_path_stop(struct gtrace_path *path);
 
+/**
+ * struct gtrace_perf_auxbuf - Representation of the perf AUX buffer.
+ * @length:   Size of the AUX buffer.
+ * @nr_pages: Number of pages of the AUX buffer.
+ * @base:     Start address of AUX buffer.
+ * @pos:      Position in the AUX buffer to commit traced data.
+ */
+struct gtrace_perf_auxbuf {
+	size_t length;
+	int nr_pages;
+	void *base;
+	long pos;
+};
+
+int gtrace_path_copyto_auxbuf(struct gtrace_path *path,
+			      struct gtrace_perf_auxbuf *buf,
+			      size_t *bytes_copied, u64 *format);
+
 /**
  * struct gtrace_driver - Representation of a trace driver.
  * @id_table:      Table to match components handled by the driver.
+ * @copyto_auxbuf: Callback to copy data into perf AUX buffer. The driver
+ *                 reports the PMU specific trace format of the copied data
+ *                 via @format (see PERF_AUX_FLAG_PMU_FORMAT_TYPE_MASK).
  * @start:         Callback to start tracing.
  * @stop:          Callback to stop tracing.
  * @probe:         Driver probe() function.
@@ -279,6 +300,9 @@ int gtrace_path_stop(struct gtrace_path *path);
  */
 struct gtrace_driver {
 	const struct gtrace_component_id *id_table;
+	size_t			(*copyto_auxbuf)(struct gtrace_component *comp,
+						 struct gtrace_perf_auxbuf *buf,
+						 u64 *format);
 	int			(*start)(struct gtrace_component *comp);
 	int			(*stop)(struct gtrace_component *comp);
 	int			(*probe)(struct gtrace_component *comp);
-- 
2.43.0