UM0851 datasheet(170/245 Pages) STMICROELECTRONICS

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Accelerator engine device drivers

UM0851

170/245

Doc ID 16604 Rev 2

Terminate DMA transfer

In some cases, DMA transfer has to be stopped due to some error condition occurring in the

client driver. This can be done using the following function.

/* It can't be called directly, call it using chan pointer:

chan->device->device_terminate_all(chan); */

void device_terminate_all(struct dma_chan *chan);

Client un-registration

After all the transfers are over, the client must free the channels so that they can be used by

some other user. For this client must un-registered itself. This can be done by the following

call:

dma_async_client_unregister(&dma_client1);

This will call dma_event() with status parameter set as DMA_RESOURCE_REMOVED.

DMA usage example

The following example transfers 100 bytes from memory to the tx_register of the skull driver.

#include <linux/spr_dmac_pl080.h>

struct dma_chan *chan;

static int src_buf[100];

struct scatterlist *sg;

u32 sg_len;

dma_cookie_t cookie;

struct dw_dma_slave dma_slave = {

.src_master = DMA_MASTER_MEMORY;

.dest_master = DMA_MASTER_SKULL;

.slave.tx_reg = (dma_addr_t)skull_tx_reg;

.slave.rx_reg = (dma_addr_t)skull_rx_reg;

.slave.reg_width = DMA_SLAVE_WIDTH_32BIT;

.cfg = DWC_CFG_FLOW_CTRL(DMA_MEMORY_TO_PERIPHERAL) |

DWC_CFG_DEST_RQID(DMA_REQ_SKULL_TX);

.ctl = DWC_CTL_USER_MODE | DWC_CTL_NON_BUFFERABLE |

DWC_CTL_NON_CACHEABLE | DWC_CTL_SRC_ADDR_INC |

DWC_CTL_DEST_BURST(BURST_8) | DWC_CTL_SRC_BURST(BURST_8) |

DWC_CTL_SRC_WIDTH(WIDTH_WORD);

}

struct dma_client dma_client = {

.event_callback = dma_event;

.slave = &dma_slave.slave;

}

static enum dma_state_client dma_event(struct dma_client *client, struct dma_chan

*chan, enum dma_state state);

void dma_xfer(void)

{

struct dma_async_tx_descriptor *tx;

u32 dma_addr;

dma_cap_set(DMA_SLAVE, dma_client.cap_mask);

/* Details of this function are not provided here.

* It will create a scatter list of 2 nodes */

sg_len = create_sg(sg, src_buf, 100);

dma_chan_get(chan);

UM0851 Datasheet(PDF) 170 Page - STMicroelectronics

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