/* ===============================================================
* The DMA ENGINE API
* ===============================================================
*/
static int pl08x_alloc_chan_resources(struct dma_chan *chan,
struct dma_client *client)
{
struct pl08x_dma_chan *local_chan = container_of
(chan, struct pl08x_dma_chan, chan);
int assigned = 0;
/*
* Channels may be reserved for slaves
* Channels doing slave DMA can only handle one client
*/
if (local_chan-<slave_only) {
if (!client-<slave)
return -EBUSY;
} else if (client-<slave)
return -EBUSY;
/* Slave DMA clients can only use one channel each */
if ((client-<slave) && (chan-<client_count))
return -EBUSY;
else {
/* Channels doing slave DMA can only handle one client. */
if ((local_chan-<slave) && (chan-<client_count)) {
dev_err(&pd.dmac-<dev,
"%s - channel %d already has a slave - local_chan-<slave %p\n",
__func__,
local_chan-<chan_id,
local_chan-<slave);
return -EBUSY;
}
/* Check channel is idle */
if (pl08x_dma_busy(local_chan-<chan_id)) {
dev_err(&pd.dmac-<dev,
"%s - channel %d not idle\n",
__func__, local_chan-<chan_id);
return -EIO;
}
local_chan-<slave = client-<slave;
}
return assigned;
}
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这部分没完全看懂,直译是用Slave DMA的channel,只能有一个client,但是具体为什么,不懂。。。 |