intel_th: msu: Introduce buffer interface

Introduces a concept of external buffers, which is a mechanism for creating
trace sinks that would receive trace data from MSC buffers and transfer it
elsewhere.

A external buffer can implement its own window allocation/deallocation if
it has to. It must provide a callback that's used to notify it when a
window fills up, so that it can then start a DMA transaction from that
window 'elsewhere'. This window remains in a 'locked' state and won't be
used for storing new trace data until the buffer 'unlocks' it with a
provided API call, at which point the window can be used again for storing
trace data.

This relies on a functional "last block" interrupt, so not all versions of
Trace Hub can use this feature, which does not reflect on existing users.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190705141425.19894-2-alexander.shishkin@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 79 insertions, 0 deletions

diff --git a/include/linux/intel_th.h b/include/linux/intel_th.h
new file mode 100644
index 000000000000..9b7f4c22499c
--- /dev/null
+++ b/include/linux/intel_th.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Intel(R) Trace Hub data structures for implementing buffer sinks.
+ *
+ * Copyright (C) 2019 Intel Corporation.
+ */
+
+#ifndef _INTEL_TH_H_
+#define _INTEL_TH_H_
+
+#include <linux/scatterlist.h>
+
+/* MSC operating modes (MSC_MODE) */
+enum {
+	MSC_MODE_SINGLE	= 0,
+	MSC_MODE_MULTI,
+	MSC_MODE_EXI,
+	MSC_MODE_DEBUG,
+};
+
+struct msu_buffer {
+	const char	*name;
+	/*
+	 * ->assign() called when buffer 'mode' is set to this driver
+	 *   (aka mode_store())
+	 * @device:	struct device * of the msc
+	 * @mode:	allows the driver to set HW mode (see the enum above)
+	 * Returns:	a pointer to a private structure associated with this
+	 *		msc or NULL in case of error. This private structure
+	 *		will then be passed into all other callbacks.
+	 */
+	void	*(*assign)(struct device *dev, int *mode);
+	/* ->unassign():	some other mode is selected, clean up */
+	void	(*unassign)(void *priv);
+	/*
+	 * ->alloc_window(): allocate memory for the window of a given
+	 *		size
+	 * @sgt:	pointer to sg_table, can be overridden by the buffer
+	 *		driver, or kept intact
+	 * Returns:	number of sg table entries <= number of pages;
+	 *		0 is treated as an allocation failure.
+	 */
+	int	(*alloc_window)(void *priv, struct sg_table **sgt,
+				size_t size);
+	void	(*free_window)(void *priv, struct sg_table *sgt);
+	/* ->activate():	trace has started */
+	void	(*activate)(void *priv);
+	/* ->deactivate():	trace is about to stop */
+	void	(*deactivate)(void *priv);
+	/*
+	 * ->ready():	window @sgt is filled up to the last block OR
+	 *		tracing is stopped by the user; this window contains
+	 *		@bytes data. The window in question transitions into
+	 *		the "LOCKED" state, indicating that it can't be used
+	 *		by hardware. To clear this state and make the window
+	 *		available to the hardware again, call
+	 *		intel_th_msc_window_unlock().
+	 */
+	int	(*ready)(void *priv, struct sg_table *sgt, size_t bytes);
+};
+
+int intel_th_msu_buffer_register(const struct msu_buffer *mbuf,
+				 struct module *owner);
+void intel_th_msu_buffer_unregister(const struct msu_buffer *mbuf);
+void intel_th_msc_window_unlock(struct device *dev, struct sg_table *sgt);
+
+#define module_intel_th_msu_buffer(__buffer) \
+static int __init __buffer##_init(void) \
+{ \
+	return intel_th_msu_buffer_register(&(__buffer), THIS_MODULE); \
+} \
+module_init(__buffer##_init); \
+static void __exit __buffer##_exit(void) \
+{ \
+	intel_th_msu_buffer_unregister(&(__buffer)); \
+} \
+module_exit(__buffer##_exit);
+
+#endif /* _INTEL_TH_H_ */