spi: atmel: Use core SPI_MASTER_MUST_[RT]X handling

We need both RX and TX data for each transfer in any case (PIO, PDC, DMA).
So convert the driver to the core dummy buffer handling with the
SPI_MASTER_MUST_RX/SPI_MASTER_MUST_TX infrastructure.

This move changes the maximum PDC/DMA buffer handling to 65535 bytes
instead of a single page and sets master->max_dma_len to this value.

All dummy buffer management is removed from the driver.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-atmel.c

@@ -303,10 +303,6 @@ struct atmel_spi {
 
 	struct completion	xfer_completion;
 
-	/* scratch buffer */
-	void			*buffer;
-	dma_addr_t		buffer_dma;
-
 	struct atmel_spi_caps	caps;
 
 	bool			use_dma;
@@ -327,7 +323,7 @@ struct atmel_spi_device {
 	u32			csr;
 };
 
-#define BUFFER_SIZE		PAGE_SIZE
+#define SPI_MAX_DMA_XFER	65535 /* true for both PDC and DMA */
 #define INVALID_DMA_ADDRESS	0xffffffff
 
 /*
@@ -612,14 +608,10 @@ static void atmel_spi_next_xfer_single(struct spi_master *master,
 		cpu_relax();
 	}
 
-	if (xfer->tx_buf) {
-		if (xfer->bits_per_word > 8)
-			spi_writel(as, TDR, *(u16 *)(xfer->tx_buf + xfer_pos));
-		else
-			spi_writel(as, TDR, *(u8 *)(xfer->tx_buf + xfer_pos));
-	} else {
-		spi_writel(as, TDR, 0);
-	}
+	if (xfer->bits_per_word > 8)
+		spi_writel(as, TDR, *(u16 *)(xfer->tx_buf + xfer_pos));
+	else
+		spi_writel(as, TDR, *(u8 *)(xfer->tx_buf + xfer_pos));
 
 	dev_dbg(master->dev.parent,
 		"  start pio xfer %p: len %u tx %p rx %p bitpw %d\n",
@@ -666,17 +658,12 @@ static void atmel_spi_next_xfer_fifo(struct spi_master *master,
 
 	/* Fill TX FIFO */
 	while (num_data >= 2) {
-		if (xfer->tx_buf) {
-			if (xfer->bits_per_word > 8) {
-				td0 = *words++;
-				td1 = *words++;
-			} else {
-				td0 = *bytes++;
-				td1 = *bytes++;
-			}
+		if (xfer->bits_per_word > 8) {
+			td0 = *words++;
+			td1 = *words++;
 		} else {
-			td0 = 0;
-			td1 = 0;
+			td0 = *bytes++;
+			td1 = *bytes++;
 		}
 
 		spi_writel(as, TDR, (td1 << 16) | td0);
@@ -684,14 +671,10 @@ static void atmel_spi_next_xfer_fifo(struct spi_master *master,
 	}
 
 	if (num_data) {
-		if (xfer->tx_buf) {
-			if (xfer->bits_per_word > 8)
-				td0 = *words++;
-			else
-				td0 = *bytes++;
-		} else {
-			td0 = 0;
-		}
+		if (xfer->bits_per_word > 8)
+			td0 = *words++;
+		else
+			td0 = *bytes++;
 
 		spi_writew(as, TDR, td0);
 		num_data--;
@@ -750,24 +733,14 @@ static int atmel_spi_next_xfer_dma_submit(struct spi_master *master,
 
 	/* prepare the RX dma transfer */
 	sg_init_table(&as->dma.sgrx, 1);
-	if (xfer->rx_buf) {
-		as->dma.sgrx.dma_address = xfer->rx_dma + xfer->len - *plen;
-	} else {
-		as->dma.sgrx.dma_address = as->buffer_dma;
-		if (len > BUFFER_SIZE)
-			len = BUFFER_SIZE;
-	}
+	as->dma.sgrx.dma_address = xfer->rx_dma + xfer->len - *plen;
 
 	/* prepare the TX dma transfer */
 	sg_init_table(&as->dma.sgtx, 1);
-	if (xfer->tx_buf) {
-		as->dma.sgtx.dma_address = xfer->tx_dma + xfer->len - *plen;
-	} else {
-		as->dma.sgtx.dma_address = as->buffer_dma;
-		if (len > BUFFER_SIZE)
-			len = BUFFER_SIZE;
-		memset(as->buffer, 0, len);
-	}
+	as->dma.sgtx.dma_address = xfer->tx_dma + xfer->len - *plen;
+
+	if (len > master->max_dma_len)
+		len = master->max_dma_len;
 
 	sg_dma_len(&as->dma.sgtx) = len;
 	sg_dma_len(&as->dma.sgrx) = len;
@@ -834,25 +807,10 @@ static void atmel_spi_next_xfer_data(struct spi_master *master,
 	struct atmel_spi	*as = spi_master_get_devdata(master);
 	u32			len = *plen;
 
-	/* use scratch buffer only when rx or tx data is unspecified */
-	if (xfer->rx_buf)
-		*rx_dma = xfer->rx_dma + xfer->len - *plen;
-	else {
-		*rx_dma = as->buffer_dma;
-		if (len > BUFFER_SIZE)
-			len = BUFFER_SIZE;
-	}
-
-	if (xfer->tx_buf)
-		*tx_dma = xfer->tx_dma + xfer->len - *plen;
-	else {
-		*tx_dma = as->buffer_dma;
-		if (len > BUFFER_SIZE)
-			len = BUFFER_SIZE;
-		memset(as->buffer, 0, len);
-		dma_sync_single_for_device(&as->pdev->dev,
-				as->buffer_dma, len, DMA_TO_DEVICE);
-	}
+	*rx_dma = xfer->rx_dma + xfer->len - *plen;
+	*tx_dma = xfer->tx_dma + xfer->len - *plen;
+	if (len > master->max_dma_len)
+		len = master->max_dma_len;
 
 	*plen = len;
 }
@@ -1026,16 +984,12 @@ atmel_spi_pump_single_data(struct atmel_spi *as, struct spi_transfer *xfer)
 	u16		*rxp16;
 	unsigned long	xfer_pos = xfer->len - as->current_remaining_bytes;
 
-	if (xfer->rx_buf) {
-		if (xfer->bits_per_word > 8) {
-			rxp16 = (u16 *)(((u8 *)xfer->rx_buf) + xfer_pos);
-			*rxp16 = spi_readl(as, RDR);
-		} else {
-			rxp = ((u8 *)xfer->rx_buf) + xfer_pos;
-			*rxp = spi_readl(as, RDR);
-		}
+	if (xfer->bits_per_word > 8) {
+		rxp16 = (u16 *)(((u8 *)xfer->rx_buf) + xfer_pos);
+		*rxp16 = spi_readl(as, RDR);
 	} else {
-		spi_readl(as, RDR);
+		rxp = ((u8 *)xfer->rx_buf) + xfer_pos;
+		*rxp = spi_readl(as, RDR);
 	}
 	if (xfer->bits_per_word > 8) {
 		if (as->current_remaining_bytes > 2)
@@ -1074,12 +1028,10 @@ atmel_spi_pump_fifo_data(struct atmel_spi *as, struct spi_transfer *xfer)
 	/* Read data */
 	while (num_data) {
 		rd = spi_readl(as, RDR);
-		if (xfer->rx_buf) {
-			if (xfer->bits_per_word > 8)
-				*words++ = rd;
-			else
-				*bytes++ = rd;
-		}
+		if (xfer->bits_per_word > 8)
+			*words++ = rd;
+		else
+			*bytes++ = rd;
 		num_data--;
 	}
 }
@@ -1561,29 +1513,22 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	master->bus_num = pdev->id;
 	master->num_chipselect = master->dev.of_node ? 0 : 4;
 	master->setup = atmel_spi_setup;
+	master->flags = (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX);
 	master->transfer_one_message = atmel_spi_transfer_one_message;
 	master->cleanup = atmel_spi_cleanup;
 	master->auto_runtime_pm = true;
+	master->max_dma_len = SPI_MAX_DMA_XFER;
 	platform_set_drvdata(pdev, master);
 
 	as = spi_master_get_devdata(master);
 
-	/*
-	 * Scratch buffer is used for throwaway rx and tx data.
-	 * It's coherent to minimize dcache pollution.
-	 */
-	as->buffer = dma_alloc_coherent(&pdev->dev, BUFFER_SIZE,
-					&as->buffer_dma, GFP_KERNEL);
-	if (!as->buffer)
-		goto out_free;
-
 	spin_lock_init(&as->lock);
 
 	as->pdev = pdev;
 	as->regs = devm_ioremap_resource(&pdev->dev, regs);
 	if (IS_ERR(as->regs)) {
 		ret = PTR_ERR(as->regs);
-		goto out_free_buffer;
+		goto out_unmap_regs;
 	}
 	as->phybase = regs->start;
 	as->irq = irq;
@@ -1681,9 +1626,6 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	clk_disable_unprepare(clk);
 out_free_irq:
 out_unmap_regs:
-out_free_buffer:
-	dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
-			as->buffer_dma);
 out_free:
 	spi_master_put(master);
 	return ret;
@@ -1708,9 +1650,6 @@ static int atmel_spi_remove(struct platform_device *pdev)
 	spi_readl(as, SR);
 	spin_unlock_irq(&as->lock);
 
-	dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
-			as->buffer_dma);
-
 	clk_disable_unprepare(as->clk);
 
 	pm_runtime_put_noidle(&pdev->dev);