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intel_th: msu: Introduce buffer interface

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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>
This commit is contained in:
Alexander Shishkin 2019-07-05 17:14:21 +03:00 • committed by Greg Kroah-Hartman
parent db4ad308a5
commit 615c164da0
5 changed files with 461 additions and 30 deletions
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79
include/linux/intel_th.h Normal file
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/* 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_ */