spi/dw_spi: refine the IRQ mode working flow

Now dw_spi core fully supports 3 transfer modes: pure polling,
DMA and IRQ mode. IRQ mode will use the FIFO half empty as
the IRQ trigger, so each interface driver need set the fifo_len,
so that core driver can handle it properly

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/dw_spi.c

@@ -358,6 +358,8 @@ static void transfer_complete(struct dw_spi *dws)
 static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 {
 	u16 irq_status, irq_mask = 0x3f;
+	u32 int_level = dws->fifo_len / 2;
+	u32 left;
 
 	irq_status = dw_readw(dws, isr) & irq_mask;
 	/* Error handling */
@@ -369,22 +371,23 @@ static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 		return IRQ_HANDLED;
 	}
 
-	/* INT comes from tx */
-	if (dws->tx && (irq_status & SPI_INT_TXEI)) {
-		while (dws->tx < dws->tx_end)
+	if (irq_status & SPI_INT_TXEI) {
+		spi_mask_intr(dws, SPI_INT_TXEI);
+
+		left = (dws->tx_end - dws->tx) / dws->n_bytes;
+		left = (left > int_level) ? int_level : left;
+
+		while (left--)
 			dws->write(dws);
+		dws->read(dws);
 
-		if (dws->tx == dws->tx_end) {
-			spi_mask_intr(dws, SPI_INT_TXEI);
+		/* Re-enable the IRQ if there is still data left to tx */
+		if (dws->tx_end > dws->tx)
+			spi_umask_intr(dws, SPI_INT_TXEI);
+		else
 			transfer_complete(dws);
-		}
 	}
 
-	/* INT comes from rx */
-	if (dws->rx && (irq_status & SPI_INT_RXFI)) {
-		if (dws->read(dws))
-			transfer_complete(dws);
-	}
 	return IRQ_HANDLED;
 }
 
@@ -428,6 +431,7 @@ static void pump_transfers(unsigned long data)
 	u8 bits = 0;
 	u8 imask = 0;
 	u8 cs_change = 0;
+	u16 txint_level = 0;
 	u16 clk_div = 0;
 	u32 speed = 0;
 	u32 cr0 = 0;
@@ -438,6 +442,9 @@ static void pump_transfers(unsigned long data)
 	chip = dws->cur_chip;
 	spi = message->spi;
 
+	if (unlikely(!chip->clk_div))
+		chip->clk_div = dws->max_freq / chip->speed_hz;
+
 	if (message->state == ERROR_STATE) {
 		message->status = -EIO;
 		goto early_exit;
@@ -492,7 +499,7 @@ static void pump_transfers(unsigned long data)
 
 			/* clk_div doesn't support odd number */
 			clk_div = dws->max_freq / speed;
-			clk_div = (clk_div >> 1) << 1;
+			clk_div = (clk_div + 1) & 0xfffe;
 
 			chip->speed_hz = speed;
 			chip->clk_div = clk_div;
@@ -535,11 +542,16 @@ static void pump_transfers(unsigned long data)
 	/* Check if current transfer is a DMA transaction */
 	dws->dma_mapped = map_dma_buffers(dws);
 
+	/*
+	 * Interrupt mode
+	 * we only need set the TXEI IRQ, as TX/RX always happen syncronizely
+	 */
 	if (!dws->dma_mapped && !chip->poll_mode) {
-		if (dws->rx)
-			imask |= SPI_INT_RXFI;
-		if (dws->tx)
-			imask |= SPI_INT_TXEI;
+		int templen = dws->len / dws->n_bytes;
+		txint_level = dws->fifo_len / 2;
+		txint_level = (templen > txint_level) ? txint_level : templen;
+
+		imask |= SPI_INT_TXEI;
 		dws->transfer_handler = interrupt_transfer;
 	}
 
@@ -549,21 +561,23 @@ static void pump_transfers(unsigned long data)
 	 *	2. clk_div is changed
 	 *	3. control value changes
 	 */
-	if (dw_readw(dws, ctrl0) != cr0 || cs_change || clk_div) {
+	if (dw_readw(dws, ctrl0) != cr0 || cs_change || clk_div || imask) {
 		spi_enable_chip(dws, 0);
 
 		if (dw_readw(dws, ctrl0) != cr0)
 			dw_writew(dws, ctrl0, cr0);
 
+		spi_set_clk(dws, clk_div ? clk_div : chip->clk_div);
+		spi_chip_sel(dws, spi->chip_select);
+
 		/* Set the interrupt mask, for poll mode just diable all int */
 		spi_mask_intr(dws, 0xff);
-		if (!chip->poll_mode)
+		if (imask)
 			spi_umask_intr(dws, imask);
+		if (txint_level)
+			dw_writew(dws, txfltr, txint_level);
 
-		spi_set_clk(dws, clk_div ? clk_div : chip->clk_div);
-		spi_chip_sel(dws, spi->chip_select);
 		spi_enable_chip(dws, 1);
-
 		if (cs_change)
 			dws->prev_chip = chip;
 	}
@@ -712,11 +726,11 @@ static int dw_spi_setup(struct spi_device *spi)
 	}
 	chip->bits_per_word = spi->bits_per_word;
 
+	if (!spi->max_speed_hz) {
+		dev_err(&spi->dev, "No max speed HZ parameter\n");
+		return -EINVAL;
+	}
 	chip->speed_hz = spi->max_speed_hz;
-	if (chip->speed_hz)
-		chip->clk_div = 25000000 / chip->speed_hz;
-	else
-		chip->clk_div = 8;	/* default value */
 
 	chip->tmode = 0; /* Tx & Rx */
 	/* Default SPI mode is SCPOL = 0, SCPH = 0 */

drivers/spi/dw_spi_pci.c

@@ -73,6 +73,7 @@ static int __devinit spi_pci_probe(struct pci_dev *pdev,
 	dws->num_cs = 4;
 	dws->max_freq = 25000000;	/* for Moorestwon */
 	dws->irq = pdev->irq;
+	dws->fifo_len = 40;		/* FIFO has 40 words buffer */
 
 	ret = dw_spi_add_host(dws);
 	if (ret)

include/linux/spi/dw_spi.h

@@ -90,6 +90,7 @@ struct dw_spi {
 	unsigned long		paddr;
 	u32			iolen;
 	int			irq;
+	u32			fifo_len;	/* depth of the FIFO buffer */
 	u32			max_freq;	/* max bus freq supported */
 
 	u16			bus_num;