drm/i915/perf: Replace gt->perf.lock with stream->lock for file ops

With multi-gt, user can access multiple OA buffers concurrently. Use
stream->lock instead of gt->perf.lock to serialize file operations.
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026222102.5526-9-umesh.nerlige.ramappa@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -3231,6 +3231,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
 	stream->poll_check_timer.function = oa_poll_check_timer_cb;
 	init_waitqueue_head(&stream->poll_wq);
 	spin_lock_init(&stream->oa_buffer.ptr_lock);
+	mutex_init(&stream->lock);
 
 	return 0;
 
@@ -3294,7 +3295,6 @@ static ssize_t i915_perf_read(struct file *file,
 			      loff_t *ppos)
 {
 	struct i915_perf_stream *stream = file->private_data;
-	struct intel_gt *gt = stream->engine->gt;
 	size_t offset = 0;
 	int ret;
 
@@ -3318,14 +3318,14 @@ static ssize_t i915_perf_read(struct file *file,
 			if (ret)
 				return ret;
 
-			mutex_lock(&gt->perf.lock);
+			mutex_lock(&stream->lock);
 			ret = stream->ops->read(stream, buf, count, &offset);
-			mutex_unlock(&gt->perf.lock);
+			mutex_unlock(&stream->lock);
 		} while (!offset && !ret);
 	} else {
-		mutex_lock(&gt->perf.lock);
+		mutex_lock(&stream->lock);
 		ret = stream->ops->read(stream, buf, count, &offset);
-		mutex_unlock(&gt->perf.lock);
+		mutex_unlock(&stream->lock);
 	}
 
 	/* We allow the poll checking to sometimes report false positive EPOLLIN
@@ -3372,9 +3372,6 @@ static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer)
  * &i915_perf_stream_ops->poll_wait to call poll_wait() with a wait queue that
  * will be woken for new stream data.
  *
- * Note: The &gt->perf.lock mutex has been taken to serialize
- * with any non-file-operation driver hooks.
- *
  * Returns: any poll events that are ready without sleeping
  */
 static __poll_t i915_perf_poll_locked(struct i915_perf_stream *stream,
@@ -3413,12 +3410,11 @@ static __poll_t i915_perf_poll_locked(struct i915_perf_stream *stream,
 static __poll_t i915_perf_poll(struct file *file, poll_table *wait)
 {
 	struct i915_perf_stream *stream = file->private_data;
-	struct intel_gt *gt = stream->engine->gt;
 	__poll_t ret;
 
-	mutex_lock(&gt->perf.lock);
+	mutex_lock(&stream->lock);
 	ret = i915_perf_poll_locked(stream, file, wait);
-	mutex_unlock(&gt->perf.lock);
+	mutex_unlock(&stream->lock);
 
 	return ret;
 }
@@ -3517,9 +3513,6 @@ static long i915_perf_config_locked(struct i915_perf_stream *stream,
  * @cmd: the ioctl request
  * @arg: the ioctl data
  *
- * Note: The &gt->perf.lock mutex has been taken to serialize
- * with any non-file-operation driver hooks.
- *
  * Returns: zero on success or a negative error code. Returns -EINVAL for
  * an unknown ioctl request.
  */
@@ -3557,12 +3550,11 @@ static long i915_perf_ioctl(struct file *file,
 			    unsigned long arg)
 {
 	struct i915_perf_stream *stream = file->private_data;
-	struct intel_gt *gt = stream->engine->gt;
 	long ret;
 
-	mutex_lock(&gt->perf.lock);
+	mutex_lock(&stream->lock);
 	ret = i915_perf_ioctl_locked(stream, cmd, arg);
-	mutex_unlock(&gt->perf.lock);
+	mutex_unlock(&stream->lock);
 
 	return ret;
 }
@@ -3608,6 +3600,11 @@ static int i915_perf_release(struct inode *inode, struct file *file)
 	struct i915_perf *perf = stream->perf;
 	struct intel_gt *gt = stream->engine->gt;
 
+	/*
+	 * Within this call, we know that the fd is being closed and we have no
+	 * other user of stream->lock. Use the perf lock to destroy the stream
+	 * here.
+	 */
 	mutex_lock(&gt->perf.lock);
 	i915_perf_destroy_locked(stream);
 	mutex_unlock(&gt->perf.lock);

drivers/gpu/drm/i915/i915_perf_types.h

@@ -146,6 +146,11 @@ struct i915_perf_stream {
 	 */
 	struct intel_engine_cs *engine;
 
+	/*
+	 * Lock associated with operations on stream
+	 */
+	struct mutex lock;
+
 	/**
 	 * @sample_flags: Flags representing the `DRM_I915_PERF_PROP_SAMPLE_*`
 	 * properties given when opening a stream, representing the contents