spi: dw: Add DMA directional capability check

Check capabilities of DMA controller during init to make sure it is
capable of handling MEM2DEV for tx channel, DEV2MEM for rx channel.

Current DW DMA driver requires both tx and rx channel to be configured
and functional for any kind of transfers to take effect including
half duplex. Hence, check for both tx and rx direction and fail on
unavailbility of either.

* tested on Baikal-T1 based system with DW SPI-looped back interface
transferring a chunk of data with DFS:8,12,16.

Signed-off-by: Joy Chakraborty <joychakr@google.com
Reviewed-by: Serge Semin <fancer.lancer@gmail.com
Tested-by: Serge Semin <fancer.lancer@gmail.com
Link: https://lore.kernel.org/r/20230512104746.1797865-2-joychakr@google.com
Signed-off-by: Mark Brown <broonie@kernel.org

drivers/spi/spi-dw-dma.c

@@ -72,12 +72,22 @@ static void dw_spi_dma_maxburst_init(struct dw_spi *dws)
 	dw_writel(dws, DW_SPI_DMATDLR, dws->txburst);
 }
 
-static void dw_spi_dma_sg_burst_init(struct dw_spi *dws)
+static int dw_spi_dma_caps_init(struct dw_spi *dws)
 {
-	struct dma_slave_caps tx = {0}, rx = {0};
+	struct dma_slave_caps tx, rx;
+	int ret;
+
+	ret = dma_get_slave_caps(dws->txchan, &tx);
+	if (ret)
+		return ret;
 
-	dma_get_slave_caps(dws->txchan, &tx);
-	dma_get_slave_caps(dws->rxchan, &rx);
+	ret = dma_get_slave_caps(dws->rxchan, &rx);
+	if (ret)
+		return ret;
+
+	if (!(tx.directions & BIT(DMA_MEM_TO_DEV) &&
+	      rx.directions & BIT(DMA_DEV_TO_MEM)))
+		return -ENXIO;
 
 	if (tx.max_sg_burst > 0 && rx.max_sg_burst > 0)
 		dws->dma_sg_burst = min(tx.max_sg_burst, rx.max_sg_burst);
@@ -87,6 +97,8 @@ static void dw_spi_dma_sg_burst_init(struct dw_spi *dws)
 		dws->dma_sg_burst = rx.max_sg_burst;
 	else
 		dws->dma_sg_burst = 0;
+
+	return 0;
 }
 
 static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
@@ -95,6 +107,7 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 	struct dw_dma_slave dma_rx = { .src_id = 0 }, *rx = &dma_rx;
 	struct pci_dev *dma_dev;
 	dma_cap_mask_t mask;
+	int ret = -EBUSY;
 
 	/*
 	 * Get pci device for DMA controller, currently it could only
@@ -124,20 +137,25 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 
 	init_completion(&dws->dma_completion);
 
-	dw_spi_dma_maxburst_init(dws);
+	ret = dw_spi_dma_caps_init(dws);
+	if (ret)
+		goto free_txchan;
 
-	dw_spi_dma_sg_burst_init(dws);
+	dw_spi_dma_maxburst_init(dws);
 
 	pci_dev_put(dma_dev);
 
 	return 0;
 
+free_txchan:
+	dma_release_channel(dws->txchan);
+	dws->txchan = NULL;
 free_rxchan:
 	dma_release_channel(dws->rxchan);
 	dws->rxchan = NULL;
 err_exit:
 	pci_dev_put(dma_dev);
-	return -EBUSY;
+	return ret;
 }
 
 static int dw_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
@@ -163,12 +181,17 @@ static int dw_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
 
 	init_completion(&dws->dma_completion);
 
-	dw_spi_dma_maxburst_init(dws);
+	ret = dw_spi_dma_caps_init(dws);
+	if (ret)
+		goto free_txchan;
 
-	dw_spi_dma_sg_burst_init(dws);
+	dw_spi_dma_maxburst_init(dws);
 
 	return 0;
 
+free_txchan:
+	dma_release_channel(dws->txchan);
+	dws->txchan = NULL;
 free_rxchan:
 	dma_release_channel(dws->rxchan);
 	dws->rxchan = NULL;