iio: proximity: vl53l0x-i2c: claim direct mode for raw readsgrafted

vl53l0x_read_raw() starts a single-shot ranging measurement and reads
back the result. Once the triggered buffer is enabled the sensor runs in
continuous mode and its data-ready interrupt is routed to the trigger,
so a concurrent in_distance_raw read disturbs the streaming setup and
never gets its completion, returning -ETIMEDOUT.

The original submission claimed direct mode here, but it was dropped
during review because the driver had no buffer support at the time [1].
Continuous (buffered) mode was later added without restoring the
claim [2], reintroducing the conflict.

Reject direct reads while buffered capture is active by claiming direct
mode around the measurement, as the vl53l1x sibling already does.

Fixes: 762186c6e7b1 ("iio: proximity: vl53l0x-i2c: Added continuous mode support")
Link: https://lore.kernel.org/linux-iio/20180911160300.GA9212@himanshu-Vostro-3559/ [1]
Link: https://lore.kernel.org/linux-iio/20240909101508.263085-3-abhashkumarjha123@gmail.com/ [2]
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/include/drm/spsc_queue.h b/include/drm/spsc_queue.h
new file mode 100644
index 000000000..ee9df8cc6
--- /dev/null
+++ b/include/drm/spsc_queue.h
@@ -0,0 +1,124 @@
+/*
+ * Copyright 2017 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef DRM_SCHEDULER_SPSC_QUEUE_H_
+#define DRM_SCHEDULER_SPSC_QUEUE_H_
+
+#include <linux/atomic.h>
+#include <linux/preempt.h>
+
+/** SPSC lockless queue */
+
+struct spsc_node {
+
+	/* Stores spsc_node* */
+	struct spsc_node *next;
+};
+
+struct spsc_queue {
+
+	 struct spsc_node *head;
+
+	/* atomic pointer to struct spsc_node* */
+	atomic_long_t tail;
+
+	atomic_t job_count;
+};
+
+static inline void spsc_queue_init(struct spsc_queue *queue)
+{
+	queue->head = NULL;
+	atomic_long_set(&queue->tail, (long)&queue->head);
+	atomic_set(&queue->job_count, 0);
+}
+
+static inline struct spsc_node *spsc_queue_peek(struct spsc_queue *queue)
+{
+	return queue->head;
+}
+
+static inline int spsc_queue_count(struct spsc_queue *queue)
+{
+	return atomic_read(&queue->job_count);
+}
+
+static inline bool spsc_queue_push(struct spsc_queue *queue, struct spsc_node *node)
+{
+	struct spsc_node **tail;
+
+	node->next = NULL;
+
+	preempt_disable();
+
+	atomic_inc(&queue->job_count);
+	smp_mb__after_atomic();
+
+	tail = (struct spsc_node **)atomic_long_xchg(&queue->tail, (long)&node->next);
+	WRITE_ONCE(*tail, node);
+
+	/*
+	 * In case of first element verify new node will be visible to the consumer
+	 * thread when we ping the kernel thread that there is new work to do.
+	 */
+	smp_wmb();
+
+	preempt_enable();
+
+	return tail == &queue->head;
+}
+
+
+static inline struct spsc_node *spsc_queue_pop(struct spsc_queue *queue)
+{
+	struct spsc_node *next, *node;
+
+	/* Verify reading from memory and not the cache */
+	smp_rmb();
+
+	node = READ_ONCE(queue->head);
+
+	if (!node)
+		return NULL;
+
+	next = READ_ONCE(node->next);
+	WRITE_ONCE(queue->head, next);
+
+	if (unlikely(!next)) {
+		/* slowpath for the last element in the queue */
+
+		if (atomic_long_cmpxchg(&queue->tail,
+				(long)&node->next, (long) &queue->head) != (long)&node->next) {
+			/* Updating tail failed wait for new next to appear */
+			do {
+				smp_rmb();
+			} while (unlikely(!(queue->head = READ_ONCE(node->next))));
+		}
+	}
+
+	atomic_dec(&queue->job_count);
+	return node;
+}
+
+
+
+#endif /* DRM_SCHEDULER_SPSC_QUEUE_H_ */