{
u16 imr = 0, dma_ctrl = 0;
+ /*
+ * Having a Rx DMA channel serviced with higher priority than a Tx DMA
+ * channel might not be enough to provide a well balanced DMA-based
+ * SPI transfer interface. There might still be moments when the Tx DMA
+ * channel is occasionally handled faster than the Rx DMA channel.
+ * That in its turn will eventually cause the SPI Rx FIFO overflow if
+ * SPI bus speed is high enough to fill the SPI Rx FIFO in before it's
+ * cleared by the Rx DMA channel. In order to fix the problem the Tx
+ * DMA activity is intentionally slowed down by limiting the SPI Tx
+ * FIFO depth with a value twice bigger than the Tx burst length
+ * calculated earlier by the dw_spi_dma_maxburst_init() method.
+ */
dw_writel(dws, DW_SPI_DMARDLR, dws->rxburst - 1);
- dw_writel(dws, DW_SPI_DMATDLR, dws->fifo_len - dws->txburst);
+ dw_writel(dws, DW_SPI_DMATDLR, dws->txburst);
if (xfer->tx_buf)
dma_ctrl |= SPI_DMA_TDMAE;