dmaengine: track the number of clients using a channel
Haavard's dma-slave interface would like to test for exclusive access to a
channel. The standard channel refcounting is not sufficient in that it
tracks more than just client references, it is also inaccurate as reference
counts are percpu until the channel is removed.
This change also enables a future fix to deallocate resources when a client
declines to use a capable channel.
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 99c22b4..10de69e 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -183,9 +183,10 @@
/* we are done once this client rejects
* an available resource
*/
- if (ack == DMA_ACK)
+ if (ack == DMA_ACK) {
dma_chan_get(chan);
- else if (ack == DMA_NAK)
+ chan->client_count++;
+ } else if (ack == DMA_NAK)
return;
}
}
@@ -272,8 +273,10 @@
/* client was holding resources for this channel so
* free it
*/
- if (ack == DMA_ACK)
+ if (ack == DMA_ACK) {
dma_chan_put(chan);
+ chan->client_count--;
+ }
}
mutex_unlock(&dma_list_mutex);
@@ -313,8 +316,10 @@
ack = client->event_callback(client, chan,
DMA_RESOURCE_REMOVED);
- if (ack == DMA_ACK)
+ if (ack == DMA_ACK) {
dma_chan_put(chan);
+ chan->client_count--;
+ }
}
list_del(&client->global_node);
@@ -394,6 +399,7 @@
kref_get(&device->refcount);
kref_get(&device->refcount);
kref_init(&chan->refcount);
+ chan->client_count = 0;
chan->slow_ref = 0;
INIT_RCU_HEAD(&chan->rcu);
}