spi: dw-dma: Check rx_buf availability in the xfer method

Checking rx_buf for being NULL and returning NULL from the Rx-channel
preparation method doesn't let us to distinguish that situation from
errors happening during the Rx SG-list preparation. So it's better to make
sure that the rx_buf not-NULL and full-duplex communication is requested
prior calling the Rx preparation method.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-dw-dma.c b/drivers/spi/spi-dw-dma.c
index da17897..d2a67de 100644 (file)
--- a/drivers/spi/spi-dw-dma.c
+++ b/drivers/spi/spi-dw-dma.c
@@ -369,9 +369,6 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi *dws,
 {
        struct dma_async_tx_descriptor *rxdesc;
 
-       if (!xfer->rx_buf)
-               return NULL;
-
        rxdesc = dmaengine_prep_slave_sg(dws->rxchan,
                                xfer->rx_sg.sgl,
                                xfer->rx_sg.nents,
@@ -435,10 +432,12 @@ static int dw_spi_dma_transfer(struct dw_spi *dws, struct spi_transfer *xfer)
                return -EINVAL;
 
        /* Prepare the RX dma transfer */
-       rxdesc = dw_spi_dma_prepare_rx(dws, xfer);
+       if (xfer->rx_buf) {
+               rxdesc = dw_spi_dma_prepare_rx(dws, xfer);
+               if (!rxdesc)
+                       return -EINVAL;
 
-       /* rx must be started before tx due to spi instinct */
-       if (rxdesc) {
+               /* 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);
@@ -458,7 +457,7 @@ static int dw_spi_dma_transfer(struct dw_spi *dws, struct spi_transfer *xfer)
                        return ret;
        }
 
-       if (rxdesc && dws->master->cur_msg->status == -EINPROGRESS)
+       if (xfer->rx_buf && dws->master->cur_msg->status == -EINPROGRESS)
                ret = dw_spi_dma_wait_rx_done(dws);
 
        return ret;