/*
* Initialize a descriptor to be used by submit
*/
static struct dma_async_tx_descriptor *pl08x_prep_dma_memcpy(
struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
size_t len, unsigned long flags)
{
struct pl08x_txd *local_txd;
local_txd = kzalloc(sizeof(struct pl08x_txd), GFP_KERNEL);
if (!local_txd) {
dev_err(&pd.dmac->dev,
"%s - no memory for descriptor\n", __func__);
return NULL;
} else {
dma_async_tx_descriptor_init(&local_txd->tx, chan);
local_txd->srcbus.addr = src;
local_txd->dstbus.addr = dest;
local_txd->tx.tx_submit = pl08x_tx_submit;
local_txd->len = len;
/*
* dmaengine.c has these directions hard coded,
* but not acessible
*/
local_txd->dstdir = DMA_FROM_DEVICE;
local_txd->srcdir = DMA_TO_DEVICE;
INIT_LIST_HEAD(&local_txd->txd_list);
/*
* Ensure the platform data for m2m is set on the channel
*/
local_txd->pcd = &pd.pd->sd[PL08X_DMA_SIGNALS];
}
return &local_txd->tx;
}
|
为DMA的memcpy做一些准备工作,主要就是初始化一些参数,尤其是传输方向 |