spi: dw-mid: split rx and tx callbacks when DMA

Currently driver wouldn't work properly if user asked for simplex transfer. The
patch separates DMA rx and tx callbacks and finishes transfer correctly in any
case.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-mid.c

@@ -26,6 +26,9 @@
 #include <linux/intel_mid_dma.h>
 #include <linux/pci.h>
 
+#define RX_BUSY		0
+#define TX_BUSY		1
+
 struct mid_dma {
 	struct intel_mid_dma_slave	dmas_tx;
 	struct intel_mid_dma_slave	dmas_rx;
@@ -98,15 +101,14 @@ static void mid_spi_dma_exit(struct dw_spi *dws)
 }
 
 /*
- * dws->dma_chan_done is cleared before the dma transfer starts,
- * callback for rx/tx channel will each increment it by 1.
- * Reaching 2 means the whole spi transaction is done.
+ * dws->dma_chan_busy is set before the dma transfer starts, callback for tx
+ * channel will clear a corresponding bit.
  */
-static void dw_spi_dma_done(void *arg)
+static void dw_spi_dma_tx_done(void *arg)
 {
 	struct dw_spi *dws = arg;
 
-	if (++dws->dma_chan_done != 2)
+	if (test_and_clear_bit(TX_BUSY, &dws->dma_chan_busy) & BIT(RX_BUSY))
 		return;
 	dw_spi_xfer_done(dws);
 }
@@ -116,6 +118,9 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_tx(struct dw_spi *dws)
 	struct dma_slave_config txconf;
 	struct dma_async_tx_descriptor *txdesc;
 
+	if (!dws->tx_dma)
+		return NULL;
+
 	txconf.direction = DMA_MEM_TO_DEV;
 	txconf.dst_addr = dws->dma_addr;
 	txconf.dst_maxburst = LNW_DMA_MSIZE_16;
@@ -134,17 +139,33 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_tx(struct dw_spi *dws)
 				1,
 				DMA_MEM_TO_DEV,
 				DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
-	txdesc->callback = dw_spi_dma_done;
+	txdesc->callback = dw_spi_dma_tx_done;
 	txdesc->callback_param = dws;
 
 	return txdesc;
 }
 
+/*
+ * dws->dma_chan_busy is set before the dma transfer starts, callback for rx
+ * channel will clear a corresponding bit.
+ */
+static void dw_spi_dma_rx_done(void *arg)
+{
+	struct dw_spi *dws = arg;
+
+	if (test_and_clear_bit(RX_BUSY, &dws->dma_chan_busy) & BIT(TX_BUSY))
+		return;
+	dw_spi_xfer_done(dws);
+}
+
 static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi *dws)
 {
 	struct dma_slave_config rxconf;
 	struct dma_async_tx_descriptor *rxdesc;
 
+	if (!dws->rx_dma)
+		return NULL;
+
 	rxconf.direction = DMA_DEV_TO_MEM;
 	rxconf.src_addr = dws->dma_addr;
 	rxconf.src_maxburst = LNW_DMA_MSIZE_16;
@@ -163,7 +184,7 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi *dws)
 				1,
 				DMA_DEV_TO_MEM,
 				DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
-	rxdesc->callback = dw_spi_dma_done;
+	rxdesc->callback = dw_spi_dma_rx_done;
 	rxdesc->callback_param = dws;
 
 	return rxdesc;
@@ -195,8 +216,6 @@ static int mid_spi_dma_transfer(struct dw_spi *dws, int cs_change)
 	if (cs_change)
 		dw_spi_dma_setup(dws);
 
-	dws->dma_chan_done = 0;
-
 	/* 2. Prepare the TX dma transfer */
 	txdesc = dw_spi_dma_prepare_tx(dws);
 
@@ -204,11 +223,17 @@ static int mid_spi_dma_transfer(struct dw_spi *dws, int cs_change)
 	rxdesc = dw_spi_dma_prepare_rx(dws);
 
 	/* rx must be started before tx due to spi instinct */
-	dmaengine_submit(rxdesc);
-	dma_async_issue_pending(dws->rxchan);
-
-	dmaengine_submit(txdesc);
-	dma_async_issue_pending(dws->txchan);
+	if (rxdesc) {
+		set_bit(RX_BUSY, &dws->dma_chan_busy);
+		dmaengine_submit(rxdesc);
+		dma_async_issue_pending(dws->rxchan);
+	}
+
+	if (txdesc) {
+		set_bit(TX_BUSY, &dws->dma_chan_busy);
+		dmaengine_submit(txdesc);
+		dma_async_issue_pending(dws->txchan);
+	}
 
 	return 0;
 }

drivers/spi/spi-dw.h

@@ -139,7 +139,7 @@ struct dw_spi {
 	struct scatterlist	tx_sgl;
 	struct dma_chan		*rxchan;
 	struct scatterlist	rx_sgl;
-	int			dma_chan_done;
+	unsigned long		dma_chan_busy;
 	struct device		*dma_dev;
 	dma_addr_t		dma_addr; /* phy address of the Data register */
 	struct dw_spi_dma_ops	*dma_ops;