[PATCH v2] spi: atmel: bounce buffer spi

[Radu Pirea]

Signed-off-by: Radu Pirea <radu.pirea at microchip.com>
---
 drivers/spi/spi-atmel.c | 112 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 82 insertions(+), 30 deletions(-)

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index f95da36..59b59ae 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -291,6 +291,10 @@ struct atmel_spi {
 	struct spi_transfer	*current_transfer;
 	int			current_remaining_bytes;
 	int			done_status;
+	dma_addr_t		dma_addr_rx_bbuf;
+	dma_addr_t		dma_addr_tx_bbuf;
+	void			*addr_rx_bbuf;
+	void			*addr_tx_bbuf;
 
 	struct completion	xfer_completion;
 
@@ -436,10 +440,15 @@ static void atmel_spi_unlock(struct atmel_spi *as) __releases(&as->lock)
 	spin_unlock_irqrestore(&as->lock, as->flags);
 }
 
+static inline bool atmel_spi_is_vmalloc_xfer(struct spi_transfer *xfer)
+{
+	return is_vmalloc_addr(xfer->tx_buf) || is_vmalloc_addr(xfer->rx_buf);
+}
+
 static inline bool atmel_spi_use_dma(struct atmel_spi *as,
 				struct spi_transfer *xfer)
 {
-	return as->use_dma && xfer->len >= DMA_MIN_BYTES;
+		return as->use_dma && xfer->len >= DMA_MIN_BYTES;
 }
 
 static bool atmel_spi_can_dma(struct spi_master *master,
@@ -448,7 +457,12 @@ static bool atmel_spi_can_dma(struct spi_master *master,
 {
 	struct atmel_spi *as = spi_master_get_devdata(master);
 
-	return atmel_spi_use_dma(as, xfer);
+	if (IS_ENABLED(CONFIG_SOC_SAM_V4_V5))
+		return atmel_spi_use_dma(as, xfer) &&
+			!atmel_spi_is_vmalloc_xfer(xfer);
+	else
+		return atmel_spi_use_dma(as, xfer);
+
 }
 
 static int atmel_spi_dma_slave_config(struct atmel_spi *as,
@@ -594,6 +608,11 @@ static void dma_callback(void *data)
 	struct spi_master	*master = data;
 	struct atmel_spi	*as = spi_master_get_devdata(master);
 
+	if (is_vmalloc_addr(as->current_transfer->rx_buf) &&
+	    IS_ENABLED(CONFIG_SOC_SAM_V4_V5)) {
+		memcpy(as->current_transfer->rx_buf, as->addr_rx_bbuf,
+		       as->current_transfer->len);
+	}
 	complete(&as->xfer_completion);
 }
 
@@ -744,17 +763,41 @@ static int atmel_spi_next_xfer_dma_submit(struct spi_master *master,
 		goto err_exit;
 
 	/* Send both scatterlists */
-	rxdesc = dmaengine_prep_slave_sg(rxchan,
-					 xfer->rx_sg.sgl, xfer->rx_sg.nents,
-					 DMA_FROM_DEVICE,
-					 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (atmel_spi_is_vmalloc_xfer(xfer) &&
+	    IS_ENABLED(CONFIG_SOC_SAM_V4_V5)) {
+		rxdesc = dmaengine_prep_slave_single(rxchan,
+						     as->dma_addr_rx_bbuf,
+						     xfer->len,
+						     DMA_FROM_DEVICE,
+						     DMA_PREP_INTERRUPT |
+						     DMA_CTRL_ACK);
+	} else {
+		rxdesc = dmaengine_prep_slave_sg(rxchan,
+						 xfer->rx_sg.sgl,
+						 xfer->rx_sg.nents,
+						 DMA_FROM_DEVICE,
+						 DMA_PREP_INTERRUPT |
+						 DMA_CTRL_ACK);
+	}
 	if (!rxdesc)
 		goto err_dma;
 
-	txdesc = dmaengine_prep_slave_sg(txchan,
-					 xfer->tx_sg.sgl, xfer->tx_sg.nents,
-					 DMA_TO_DEVICE,
-					 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (atmel_spi_is_vmalloc_xfer(xfer) &&
+	    IS_ENABLED(CONFIG_SOC_SAM_V4_V5)) {
+		memcpy(as->addr_tx_bbuf, xfer->tx_buf, xfer->len);
+		txdesc = dmaengine_prep_slave_single(txchan,
+						     as->dma_addr_tx_bbuf,
+						     xfer->len, DMA_TO_DEVICE,
+						     DMA_PREP_INTERRUPT |
+						     DMA_CTRL_ACK);
+	} else {
+		txdesc = dmaengine_prep_slave_sg(txchan,
+						 xfer->tx_sg.sgl,
+						 xfer->tx_sg.nents,
+						 DMA_TO_DEVICE,
+						 DMA_PREP_INTERRUPT |
+						 DMA_CTRL_ACK);
+	}
 	if (!txdesc)
 		goto err_dma;
 
@@ -1426,27 +1469,7 @@ static void atmel_get_caps(struct atmel_spi *as)
 
 	as->caps.is_spi2 = version > 0x121;
 	as->caps.has_wdrbt = version >= 0x210;
-#ifdef CONFIG_SOC_SAM_V4_V5
-	/*
-	 * Atmel SoCs based on ARM9 (SAM9x) cores should not use spi_map_buf()
-	 * since this later function tries to map buffers with dma_map_sg()
-	 * even if they have not been allocated inside DMA-safe areas.
-	 * On SoCs based on Cortex A5 (SAMA5Dx), it works anyway because for
-	 * those ARM cores, the data cache follows the PIPT model.
-	 * Also the L2 cache controller of SAMA5D2 uses the PIPT model too.
-	 * In case of PIPT caches, there cannot be cache aliases.
-	 * However on ARM9 cores, the data cache follows the VIVT model, hence
-	 * the cache aliases issue can occur when buffers are allocated from
-	 * DMA-unsafe areas, by vmalloc() for instance, where cache coherency is
-	 * not taken into account or at least not handled completely (cache
-	 * lines of aliases are not invalidated).
-	 * This is not a theorical issue: it was reproduced when trying to mount
-	 * a UBI file-system on a at91sam9g35ek board.
-	 */
-	as->caps.has_dma_support = false;
-#else
 	as->caps.has_dma_support = version >= 0x212;
-#endif
 	as->caps.has_pdc_support = version < 0x212;
 }
 
@@ -1592,6 +1615,27 @@ static int atmel_spi_probe(struct platform_device *pdev)
 		as->use_pdc = true;
 	}
 
+	if (IS_ENABLED(CONFIG_SOC_SAM_V4_V5)) {
+		as->addr_rx_bbuf = dma_alloc_coherent(&pdev->dev,
+						      SPI_MAX_DMA_XFER,
+						      &as->dma_addr_rx_bbuf,
+						      GFP_KERNEL | GFP_DMA);
+		if (!as->addr_rx_bbuf) {
+			as->use_dma = false;
+		} else {
+			as->addr_tx_bbuf = dma_alloc_coherent(&pdev->dev,
+					SPI_MAX_DMA_XFER,
+					&as->dma_addr_tx_bbuf,
+					GFP_KERNEL | GFP_DMA);
+			if (!as->addr_tx_bbuf) {
+				as->use_dma = false;
+				dma_free_coherent(&pdev->dev, SPI_MAX_DMA_XFER,
+						  as->addr_rx_bbuf,
+						  as->dma_addr_rx_bbuf);
+			}
+		}
+	}
+
 	if (as->caps.has_dma_support && !as->use_dma)
 		dev_info(&pdev->dev, "Atmel SPI Controller using PIO only\n");
 
@@ -1665,6 +1709,14 @@ static int atmel_spi_remove(struct platform_device *pdev)
 	if (as->use_dma) {
 		atmel_spi_stop_dma(master);
 		atmel_spi_release_dma(master);
+		if (IS_ENABLED(CONFIG_SOC_SAM_V4_V5)) {
+			dma_free_coherent(&pdev->dev, SPI_MAX_DMA_XFER,
+					  as->addr_tx_bbuf,
+					  as->dma_addr_tx_bbuf);
+			dma_free_coherent(&pdev->dev, SPI_MAX_DMA_XFER,
+					  as->addr_rx_bbuf,
+					  as->dma_addr_rx_bbuf);
+		}
 	}
 
 	spi_writel(as, CR, SPI_BIT(SWRST));
-- 
2.7.4