spi/dw_spi: improve the interrupt mode with the batch ops

leverage the performance gain by change in low level
read/write batch operations

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

drivers/spi/dw_spi.c

@@ -190,21 +190,7 @@ static inline u32 rx_max(struct dw_spi *dws)
 	return min(rx_left, (u32)dw_readw(dws, rxflr));
 }
 
-
-static void wait_till_not_busy(struct dw_spi *dws)
-{
-	unsigned long end = jiffies + 1 + usecs_to_jiffies(5000);
-
-	while (time_before(jiffies, end)) {
-		if (!(dw_readw(dws, sr) & SR_BUSY))
-			return;
-		cpu_relax();
-	}
-	dev_err(&dws->master->dev,
-		"DW SPI: Status keeps busy for 5000us after a read/write!\n");
-}
-
-static int dw_writer(struct dw_spi *dws)
+static void dw_writer(struct dw_spi *dws)
 {
 	u32 max = tx_max(dws);
 	u16 txw = 0;
@@ -220,11 +206,9 @@ static int dw_writer(struct dw_spi *dws)
 		dw_writew(dws, dr, txw);
 		dws->tx += dws->n_bytes;
 	}
-
-	return 1;
 }
 
-static int dw_reader(struct dw_spi *dws)
+static void dw_reader(struct dw_spi *dws)
 {
 	u32 max = rx_max(dws);
 	u16 rxw;
@@ -240,8 +224,6 @@ static int dw_reader(struct dw_spi *dws)
 		}
 		dws->rx += dws->n_bytes;
 	}
-
-	return dws->rx == dws->rx_end;
 }
 
 static void *next_transfer(struct dw_spi *dws)
@@ -340,35 +322,28 @@ EXPORT_SYMBOL_GPL(dw_spi_xfer_done);
 
 static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 {
-	u16 irq_status, irq_mask = 0x3f;
-	u32 int_level = dws->fifo_len / 2;
-	u32 left;
+	u16 irq_status = dw_readw(dws, isr);
 
-	irq_status = dw_readw(dws, isr) & irq_mask;
 	/* Error handling */
 	if (irq_status & (SPI_INT_TXOI | SPI_INT_RXOI | SPI_INT_RXUI)) {
 		dw_readw(dws, txoicr);
 		dw_readw(dws, rxoicr);
 		dw_readw(dws, rxuicr);
-		int_error_stop(dws, "interrupt_transfer: fifo overrun");
+		int_error_stop(dws, "interrupt_transfer: fifo overrun/underrun");
 		return IRQ_HANDLED;
 	}
 
+	dw_reader(dws);
+	if (dws->rx_end == dws->rx) {
+		spi_mask_intr(dws, SPI_INT_TXEI);
+		dw_spi_xfer_done(dws);
+		return IRQ_HANDLED;
+	}
 	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--)
-			dw_writer(dws);
-		dw_reader(dws);
-
-		/* 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
-			dw_spi_xfer_done(dws);
+		dw_writer(dws);
+		/* Enable TX irq always, it will be disabled when RX finished */
+		spi_umask_intr(dws, SPI_INT_TXEI);
 	}
 
 	return IRQ_HANDLED;
@@ -377,15 +352,13 @@ static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 static irqreturn_t dw_spi_irq(int irq, void *dev_id)
 {
 	struct dw_spi *dws = dev_id;
-	u16 irq_status, irq_mask = 0x3f;
+	u16 irq_status = dw_readw(dws, isr) & 0x3f;
 
-	irq_status = dw_readw(dws, isr) & irq_mask;
 	if (!irq_status)
 		return IRQ_NONE;
 
 	if (!dws->cur_msg) {
 		spi_mask_intr(dws, SPI_INT_TXEI);
-		/* Never fail */
 		return IRQ_HANDLED;
 	}
 
@@ -492,12 +465,8 @@ static void pump_transfers(unsigned long data)
 
 		switch (bits) {
 		case 8:
-			dws->n_bytes = 1;
-			dws->dma_width = 1;
-			break;
 		case 16:
-			dws->n_bytes = 2;
-			dws->dma_width = 2;
+			dws->n_bytes = dws->dma_width = bits >> 3;
 			break;
 		default:
 			printk(KERN_ERR "MRST SPI0: unsupported bits:"
@@ -541,7 +510,7 @@ static void pump_transfers(unsigned long data)
 		txint_level = dws->fifo_len / 2;
 		txint_level = (templen > txint_level) ? txint_level : templen;
 
-		imask |= SPI_INT_TXEI;
+		imask |= SPI_INT_TXEI | SPI_INT_TXOI | SPI_INT_RXUI | SPI_INT_RXOI;
 		dws->transfer_handler = interrupt_transfer;
 	}