[PATCH v2 1/3] spi: rockchip: Config spi rx dma burst size depend on xfer length

[Jon Lin]

The burst length can be adjusted according to the transmission
length to improve the transmission rate

Signed-off-by: Jon Lin <jon....@rock-chips.com>
---
 drivers/spi/spi-rockchip.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 9b8a5e1233c0..63593a5b87fa 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -384,6 +384,19 @@ static void rockchip_spi_dma_txcb(void *data)
        spi_finalize_current_transfer(ctlr);
 }
 
+static u32 rockchip_spi_calc_burst_size(u32 data_len)
+{
+       u32 i;
+
+       /* burst size: 1, 2, 4, 8 */
+       for (i = 1; i < 8; i <<= 1) {
+               if (data_len & i)
+                       break;
+       }
+
+       return i;
+}
+
 static int rockchip_spi_prepare_dma(struct rockchip_spi *rs,
                struct spi_controller *ctlr, struct spi_transfer *xfer)
 {
@@ -397,7 +410,8 @@ static int rockchip_spi_prepare_dma(struct rockchip_spi *rs,
                        .direction = DMA_DEV_TO_MEM,
                        .src_addr = rs->dma_addr_rx,
                        .src_addr_width = rs->n_bytes,
-                       .src_maxburst = 1,
+                       .src_maxburst = rockchip_spi_calc_burst_size(xfer->len /
+                                                                    
rs->n_bytes),
                };
 
                dmaengine_slave_config(ctlr->dma_rx, &rxconf);
@@ -525,7 +539,8 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
                writel_relaxed(rs->fifo_len / 2 - 1, rs->regs + 
ROCKCHIP_SPI_RXFTLR);
 
        writel_relaxed(rs->fifo_len / 2, rs->regs + ROCKCHIP_SPI_DMATDLR);
-       writel_relaxed(0, rs->regs + ROCKCHIP_SPI_DMARDLR);
+       writel_relaxed(rockchip_spi_calc_burst_size(xfer->len / rs->n_bytes) - 
1,
+                      rs->regs + ROCKCHIP_SPI_DMARDLR);
        writel_relaxed(dmacr, rs->regs + ROCKCHIP_SPI_DMACR);
 
        /* the hardware only supports an even clock divisor, so
-- 
2.17.1