Enable DMA support on i.mx6. The read speed can increase from 600KB/s
to 1.2MB/s on i.mx6q. You can disable or enable dma function in dts.
+
+static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
+ struct spi_master *master,
+ const struct resource *res)
+{
+ struct dma_slave_config slave_config = {};
+ int ret;
+
+ /* Prepare for TX DMA: */
+ master->dma_tx = dma_request_slave_channel(dev, "tx");
+ if (!master->dma_tx) {
+ dev_err(dev, "cannot get the TX DMA channel!\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ slave_config.dst_addr = res->start + MXC_CSPITXDATA;
+ slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
+ ret = dmaengine_slave_config(master->dma_tx, &slave_config);
+ if (ret) {
+ dev_err(dev, "error in TX dma configuration.");
+