[PATCH v2 05/11] spi: dw-dma: Move DMA transfers submission to the channels prep methods

[Serge Semin]

Indeed we can freely move the dmaengine_submit() method invocation and the
Tx and Rx busy flag setting into the DMA Tx/Rx prepare methods. Since the
Tx/Rx preparation method is now mainly used for the DMA transfers
submission, here we suggest to rename it to have the _submit_{r,t}x suffix
instead.

By having this alteration applied first we implement another code
preparation before adding the one-by-one DMA SG entries transmission,
second we now have the dma_async_tx_descriptor descriptor used locally
only in the new DMA transfers submission methods (this will be cleaned up
a bit later), third we make the generic transfer method more readable,
where now the functionality of submission, execution and wait procedures
is transparently split up instead of having a preparation, intermixed
submission/execution and wait procedures.

Signed-off-by: Serge Semin <sergey.se...@baikalelectronics.ru>
---
 drivers/spi/spi-dw-dma.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-dw-dma.c b/drivers/spi/spi-dw-dma.c
index d2a67dee1a66..769d10ca74b4 100644
--- a/drivers/spi/spi-dw-dma.c
+++ b/drivers/spi/spi-dw-dma.c
@@ -272,7 +272,7 @@ static int dw_spi_dma_config_tx(struct dw_spi *dws)
 }
 
 static struct dma_async_tx_descriptor *
-dw_spi_dma_prepare_tx(struct dw_spi *dws, struct spi_transfer *xfer)
+dw_spi_dma_submit_tx(struct dw_spi *dws, struct spi_transfer *xfer)
 {
        struct dma_async_tx_descriptor *txdesc;
 
@@ -287,6 +287,9 @@ dw_spi_dma_prepare_tx(struct dw_spi *dws, struct 
spi_transfer *xfer)
        txdesc->callback = dw_spi_dma_tx_done;
        txdesc->callback_param = dws;
 
+       dmaengine_submit(txdesc);
+       set_bit(TX_BUSY, &dws->dma_chan_busy);
+
        return txdesc;
 }
 
@@ -364,7 +367,7 @@ static int dw_spi_dma_config_rx(struct dw_spi *dws)
        return dmaengine_slave_config(dws->rxchan, &rxconf);
 }
 
-static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi 
*dws,
+static struct dma_async_tx_descriptor *dw_spi_dma_submit_rx(struct dw_spi *dws,
                struct spi_transfer *xfer)
 {
        struct dma_async_tx_descriptor *rxdesc;
@@ -380,6 +383,9 @@ static struct dma_async_tx_descriptor 
*dw_spi_dma_prepare_rx(struct dw_spi *dws,
        rxdesc->callback = dw_spi_dma_rx_done;
        rxdesc->callback_param = dws;
 
+       dmaengine_submit(rxdesc);
+       set_bit(RX_BUSY, &dws->dma_chan_busy);
+
        return rxdesc;
 }
 
@@ -426,25 +432,21 @@ static int dw_spi_dma_transfer(struct dw_spi *dws, struct 
spi_transfer *xfer)
        struct dma_async_tx_descriptor *txdesc, *rxdesc;
        int ret;
 
-       /* Prepare the TX dma transfer */
-       txdesc = dw_spi_dma_prepare_tx(dws, xfer);
+       /* Submit the DMA Tx transfer */
+       txdesc = dw_spi_dma_submit_tx(dws, xfer);
        if (!txdesc)
                return -EINVAL;
 
-       /* Prepare the RX dma transfer */
+       /* Submit the DMA Rx transfer if required */
        if (xfer->rx_buf) {
-               rxdesc = dw_spi_dma_prepare_rx(dws, xfer);
+               rxdesc = dw_spi_dma_submit_rx(dws, xfer);
                if (!rxdesc)
                        return -EINVAL;
 
                /* rx must be started before tx due to spi instinct */
-               set_bit(RX_BUSY, &dws->dma_chan_busy);
-               dmaengine_submit(rxdesc);
                dma_async_issue_pending(dws->rxchan);
        }
 
-       set_bit(TX_BUSY, &dws->dma_chan_busy);
-       dmaengine_submit(txdesc);
        dma_async_issue_pending(dws->txchan);
 
        ret = dw_spi_dma_wait(dws, xfer);
-- 
2.27.0