media: vivid: add signal-free time for cec message xfer

Currently, the vivid emulation of cec message transmission does not force
adapters to wait until the cec bus has been signal-free for a certain
number of bit periods before transmitting or re-transmitting a message.
Without enforcing the signal-free time requirements, adapters do not share
the bus very well and some messages are sent too quickly while other
messages are lost. By emulating a signal-free time and forcing adapters
to wait their turn to transmit, the vivid emulation of cec transmission
is much more reliable.
Signed-off-by: Deborah Brouwer <deborahbrouwer3563@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/test-drivers/vivid/vivid-cec.h

@@ -9,12 +9,5 @@
 struct cec_adapter *vivid_cec_alloc_adap(struct vivid_dev *dev,
 					 unsigned int idx,
 					 bool is_source);
-void vivid_cec_bus_free_work(struct vivid_dev *dev);
-
-#else
-
-static inline void vivid_cec_bus_free_work(struct vivid_dev *dev)
-{
-}
-
+int vivid_cec_bus_thread(void *_dev);
 #endif

drivers/media/test-drivers/vivid/vivid-core.c

@@ -1888,18 +1888,7 @@ static int vivid_create_instance(struct platform_device *pdev, int inst)
 	INIT_LIST_HEAD(&dev->meta_out_active);
 	INIT_LIST_HEAD(&dev->touch_cap_active);
 
-	INIT_LIST_HEAD(&dev->cec_work_list);
-	spin_lock_init(&dev->cec_slock);
-	/*
-	 * Same as create_singlethread_workqueue, but now I can use the
-	 * string formatting of alloc_ordered_workqueue.
-	 */
-	dev->cec_workqueue = alloc_ordered_workqueue("vivid-%03d-cec",
-						     WQ_MEM_RECLAIM, inst);
-	if (!dev->cec_workqueue) {
-		ret = -ENOMEM;
-		goto unreg_dev;
-	}
+	spin_lock_init(&dev->cec_xfers_slock);
 
 	if (allocators[inst] == 1)
 		dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
@@ -1939,6 +1928,19 @@ static int vivid_create_instance(struct platform_device *pdev, int inst)
 			cec_tx_bus_cnt++;
 		}
 	}
+
+	if (dev->cec_rx_adap || cec_tx_bus_cnt) {
+		init_waitqueue_head(&dev->kthread_waitq_cec);
+		dev->kthread_cec = kthread_run(vivid_cec_bus_thread, dev,
+					       "vivid_cec-%s", dev->v4l2_dev.name);
+		if (IS_ERR(dev->kthread_cec)) {
+			dev->kthread_cec = NULL;
+			v4l2_err(&dev->v4l2_dev, "kernel_thread() failed\n");
+			ret = PTR_ERR(dev->kthread_cec);
+			goto unreg_dev;
+		}
+	}
+
 #endif
 
 	v4l2_ctrl_handler_setup(&dev->ctrl_hdl_vid_cap);
@@ -1978,10 +1980,8 @@ static int vivid_create_instance(struct platform_device *pdev, int inst)
 	cec_unregister_adapter(dev->cec_rx_adap);
 	for (i = 0; i < MAX_OUTPUTS; i++)
 		cec_unregister_adapter(dev->cec_tx_adap[i]);
-	if (dev->cec_workqueue) {
-		vivid_cec_bus_free_work(dev);
-		destroy_workqueue(dev->cec_workqueue);
-	}
+	if (dev->kthread_cec)
+		kthread_stop(dev->kthread_cec);
 free_dev:
 	v4l2_device_put(&dev->v4l2_dev);
 	return ret;
@@ -2103,10 +2103,8 @@ static int vivid_remove(struct platform_device *pdev)
 		cec_unregister_adapter(dev->cec_rx_adap);
 		for (j = 0; j < MAX_OUTPUTS; j++)
 			cec_unregister_adapter(dev->cec_tx_adap[j]);
-		if (dev->cec_workqueue) {
-			vivid_cec_bus_free_work(dev);
-			destroy_workqueue(dev->cec_workqueue);
-		}
+		if (dev->kthread_cec)
+			kthread_stop(dev->kthread_cec);
 		v4l2_device_put(&dev->v4l2_dev);
 		vivid_devs[i] = NULL;
 	}

drivers/media/test-drivers/vivid/vivid-core.h

@@ -110,15 +110,11 @@ enum vivid_colorspace {
 #define VIVID_INVALID_SIGNAL(mode) \
 	((mode) == NO_SIGNAL || (mode) == NO_LOCK || (mode) == OUT_OF_RANGE)
 
-struct vivid_cec_work {
-	struct list_head	list;
-	struct delayed_work	work;
+struct vivid_cec_xfer {
 	struct cec_adapter	*adap;
-	struct vivid_dev	*dev;
-	unsigned int		usecs;
-	unsigned int		timeout_ms;
-	u8			tx_status;
-	struct cec_msg		msg;
+	u8			msg[CEC_MAX_MSG_SIZE];
+	u32			len;
+	u32			sft;
 };
 
 struct vivid_dev {
@@ -560,12 +556,13 @@ struct vivid_dev {
 	/* CEC */
 	struct cec_adapter		*cec_rx_adap;
 	struct cec_adapter		*cec_tx_adap[MAX_OUTPUTS];
-	struct workqueue_struct		*cec_workqueue;
-	spinlock_t			cec_slock;
-	struct list_head		cec_work_list;
-	unsigned int			cec_xfer_time_jiffies;
-	unsigned long			cec_xfer_start_jiffies;
 	u8				cec_output2bus_map[MAX_OUTPUTS];
+	struct task_struct		*kthread_cec;
+	wait_queue_head_t		kthread_waitq_cec;
+	struct vivid_cec_xfer	xfers[MAX_OUTPUTS];
+	spinlock_t			cec_xfers_slock; /* read and write cec messages */
+	u32				cec_sft; /* bus signal free time, in bit periods */
+	u8				last_initiator;
 
 	/* CEC OSD String */
 	char				osd[14];