coresight: stm: adding driver for CoreSight STM component

This driver adds support for the STM CoreSight IP block, allowing any
system compoment (HW or SW) to log and aggregate messages via a
single entity.

The CoreSight STM exposes an application defined number of channels
called stimulus port.  Configuration is done using entries in sysfs
and channels made available to userspace via configfs.

Signed-off-by: Pratik Patel <pratikp@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Michael Williams <michael.williams@arm.com>
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 237483aa5c)

include/uapi/linux/coresight-stm.h

@@ -0,0 +1,21 @@
+#ifndef __UAPI_CORESIGHT_STM_H_
+#define __UAPI_CORESIGHT_STM_H_
+
+#define STM_FLAG_TIMESTAMPED   BIT(3)
+#define STM_FLAG_GUARANTEED    BIT(7)
+
+/*
+ * The CoreSight STM supports guaranteed and invariant timing
+ * transactions.  Guaranteed transactions are guaranteed to be
+ * traced, this might involve stalling the bus or system to
+ * ensure the transaction is accepted by the STM.  While invariant
+ * timing transactions are not guaranteed to be traced, they
+ * will take an invariant amount of time regardless of the
+ * state of the STM.
+ */
+enum {
+	STM_OPTION_GUARANTEED = 0,
+	STM_OPTION_INVARIANT,
+};
+
+#endif