staging: most: add fair buffer distribution

This patch ensures a fair distribution of buffers, when two AIMs share a
single channel. The AIMs then won't be able to use more than half of all
pre-allocated buffers of the linked channel. However, in case the channel
is not shared, the AIM can exclusively use all available buffers.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/aim-cdev/cdev.c

@@ -165,7 +165,7 @@ static ssize_t aim_write(struct file *filp, const char __user *buf,
 	}
 	mutex_unlock(&channel->io_mutex);
 
-	mbo = most_get_mbo(channel->iface, channel->channel_id);
+	mbo = most_get_mbo(channel->iface, channel->channel_id, &cdev_aim);
 
 	if (!mbo) {
 		if ((filp->f_flags & O_NONBLOCK))
@@ -173,7 +173,8 @@ static ssize_t aim_write(struct file *filp, const char __user *buf,
 		if (wait_event_interruptible(
 			    channel->wq,
 			    (mbo = most_get_mbo(channel->iface,
-						channel->channel_id)) ||
+						channel->channel_id,
+						&cdev_aim)) ||
 			    (!channel->dev)))
 			return -ERESTARTSYS;
 	}

drivers/staging/most/aim-network/networking.c

@@ -245,7 +245,7 @@ static netdev_tx_t most_nd_start_xmit(struct sk_buff *skb,
 
 	BUG_ON(nd->dev != dev);
 
-	mbo = most_get_mbo(nd->iface, nd->tx.ch_id);
+	mbo = most_get_mbo(nd->iface, nd->tx.ch_id, &aim);
 
 	if (!mbo) {
 		netif_stop_queue(dev);

drivers/staging/most/aim-sound/sound.c

@@ -251,7 +251,8 @@ static int playback_thread(void *data)
 		wait_event_interruptible(
 			channel->playback_waitq,
 			kthread_should_stop() ||
-			(mbo = most_get_mbo(channel->iface, channel->id)));
+			(mbo = most_get_mbo(channel->iface, channel->id,
+					    &audio_aim)));
 
 		if (!mbo)
 			continue;

drivers/staging/most/hdm-dim2/dim2_hdm.c

@@ -669,7 +669,7 @@ static void request_netinfo(struct most_interface *most_iface, int ch_idx)
 		return;
 	}
 
-	mbo = most_get_mbo(&dev->most_iface, dev->atx_idx);
+	mbo = most_get_mbo(&dev->most_iface, dev->atx_idx, NULL);
 	if (!mbo)
 		return;
 

drivers/staging/most/mostcore/core.c

@@ -36,6 +36,7 @@ static struct class *most_class;
 static struct device *class_glue_dir;
 static struct ida mdev_id;
 static int modref;
+static int dummy_num_buffers;
 
 struct most_c_obj {
 	struct kobject kobj;
@@ -59,6 +60,8 @@ struct most_c_obj {
 	struct most_aim *second_aim;
 	int first_aim_refs;
 	int second_aim_refs;
+	int first_num_buffers;
+	int second_num_buffers;
 	struct list_head trash_fifo;
 	struct task_struct *hdm_enqueue_task;
 	struct mutex stop_task_mutex;
@@ -1233,6 +1236,7 @@ static void arm_mbo(struct mbo *mbo)
 	}
 
 	spin_lock_irqsave(&c->fifo_lock, flags);
+	++*mbo->num_buffers_ptr;
 	list_add_tail(&mbo->list, &c->fifo);
 	spin_unlock_irqrestore(&c->fifo_lock, flags);
 
@@ -1286,6 +1290,7 @@ static int arm_mbo_chain(struct most_c_obj *c, int dir,
 			goto _error1;
 		}
 		mbo->complete = compl;
+		mbo->num_buffers_ptr = &dummy_num_buffers;
 		if (dir == MOST_CH_RX) {
 			nq_hdm_mbo(mbo);
 			atomic_inc(&c->mbo_nq_level);
@@ -1384,22 +1389,40 @@ most_c_obj *get_channel_by_iface(struct most_interface *iface, int id)
  * This attempts to get a free buffer out of the channel fifo.
  * Returns a pointer to MBO on success or NULL otherwise.
  */
-struct mbo *most_get_mbo(struct most_interface *iface, int id)
+struct mbo *most_get_mbo(struct most_interface *iface, int id,
+			 struct most_aim *aim)
 {
 	struct mbo *mbo;
 	struct most_c_obj *c;
 	unsigned long flags;
+	int *num_buffers_ptr;
 
 	c = get_channel_by_iface(iface, id);
 	if (unlikely(!c))
 		return NULL;
+
+	if (c->first_aim_refs && c->second_aim_refs &&
+	    ((aim == c->first_aim && c->first_num_buffers <= 0) ||
+	     (aim == c->second_aim && c->second_num_buffers <= 0)))
+		return NULL;
+
+	if (aim == c->first_aim)
+		num_buffers_ptr = &c->first_num_buffers;
+	else if (aim == c->second_aim)
+		num_buffers_ptr = &c->second_num_buffers;
+	else
+		num_buffers_ptr = &dummy_num_buffers;
+
 	spin_lock_irqsave(&c->fifo_lock, flags);
 	if (list_empty(&c->fifo)) {
 		spin_unlock_irqrestore(&c->fifo_lock, flags);
 		return NULL;
 	}
 	mbo = list_pop_mbo(&c->fifo);
+	--*num_buffers_ptr;
 	spin_unlock_irqrestore(&c->fifo_lock, flags);
+
+	mbo->num_buffers_ptr = num_buffers_ptr;
 	mbo->buffer_length = c->cfg.buffer_size;
 	return mbo;
 }
@@ -1530,6 +1553,8 @@ int most_start_channel(struct most_interface *iface, int id,
 		goto error;
 
 	c->is_starving = 0;
+	c->first_num_buffers = c->cfg.num_buffers / 2;
+	c->second_num_buffers = c->cfg.num_buffers - c->first_num_buffers;
 	atomic_set(&c->mbo_ref, num_buffer);
 
 out:

drivers/staging/most/mostcore/mostcore.h

@@ -190,6 +190,7 @@ struct mbo {
 	void *priv;
 	struct list_head list;
 	struct most_interface *ifp;
+	int *num_buffers_ptr;
 	u16 hdm_channel_id;
 	void *virt_address;
 	dma_addr_t bus_address;
@@ -307,7 +308,8 @@ void most_stop_enqueue(struct most_interface *iface, int channel_idx);
 void most_resume_enqueue(struct most_interface *iface, int channel_idx);
 int most_register_aim(struct most_aim *aim);
 int most_deregister_aim(struct most_aim *aim);
-struct mbo *most_get_mbo(struct most_interface *iface, int channel_idx);
+struct mbo *most_get_mbo(struct most_interface *iface, int channel_idx,
+			 struct most_aim *);
 void most_put_mbo(struct mbo *mbo);
 int most_start_channel(struct most_interface *iface, int channel_idx,
 		       struct most_aim *);