spi/dw_spi: unify the low level read/write routines

The original version has many duplicated codes for null/u8/u16 case,
so unify them to make it cleaner

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

drivers/spi/dw_spi.c

@@ -58,8 +58,6 @@ struct chip_data {
 	u8 bits_per_word;
 	u16 clk_div;		/* baud rate divider */
 	u32 speed_hz;		/* baud rate */
-	int (*write)(struct dw_spi *dws);
-	int (*read)(struct dw_spi *dws);
 	void (*cs_control)(u32 command);
 };
 
@@ -185,80 +183,45 @@ static void flush(struct dw_spi *dws)
 	wait_till_not_busy(dws);
 }
 
-static int null_writer(struct dw_spi *dws)
-{
-	u8 n_bytes = dws->n_bytes;
-
-	if (!(dw_readw(dws, sr) & SR_TF_NOT_FULL)
-		|| (dws->tx == dws->tx_end))
-		return 0;
-	dw_writew(dws, dr, 0);
-	dws->tx += n_bytes;
 
-	wait_till_not_busy(dws);
-	return 1;
-}
-
-static int null_reader(struct dw_spi *dws)
+static int dw_writer(struct dw_spi *dws)
 {
-	u8 n_bytes = dws->n_bytes;
+	u16 txw = 0;
 
-	while ((dw_readw(dws, sr) & SR_RF_NOT_EMPT)
-		&& (dws->rx < dws->rx_end)) {
-		dw_readw(dws, dr);
-		dws->rx += n_bytes;
-	}
-	wait_till_not_busy(dws);
-	return dws->rx == dws->rx_end;
-}
-
-static int u8_writer(struct dw_spi *dws)
-{
 	if (!(dw_readw(dws, sr) & SR_TF_NOT_FULL)
 		|| (dws->tx == dws->tx_end))
 		return 0;
 
-	dw_writew(dws, dr, *(u8 *)(dws->tx));
-	++dws->tx;
-
-	wait_till_not_busy(dws);
-	return 1;
-}
-
-static int u8_reader(struct dw_spi *dws)
-{
-	while ((dw_readw(dws, sr) & SR_RF_NOT_EMPT)
-		&& (dws->rx < dws->rx_end)) {
-		*(u8 *)(dws->rx) = dw_readw(dws, dr);
-		++dws->rx;
+	/* Set the tx word if the transfer's original "tx" is not null */
+	if (dws->tx_end - dws->len) {
+		if (dws->n_bytes == 1)
+			txw = *(u8 *)(dws->tx);
+		else
+			txw = *(u16 *)(dws->tx);
 	}
 
-	wait_till_not_busy(dws);
-	return dws->rx == dws->rx_end;
-}
-
-static int u16_writer(struct dw_spi *dws)
-{
-	if (!(dw_readw(dws, sr) & SR_TF_NOT_FULL)
-		|| (dws->tx == dws->tx_end))
-		return 0;
-
-	dw_writew(dws, dr, *(u16 *)(dws->tx));
-	dws->tx += 2;
+	dw_writew(dws, dr, txw);
+	dws->tx += dws->n_bytes;
 
 	wait_till_not_busy(dws);
 	return 1;
 }
 
-static int u16_reader(struct dw_spi *dws)
+static int dw_reader(struct dw_spi *dws)
 {
-	u16 temp;
+	u16 rxw;
 
 	while ((dw_readw(dws, sr) & SR_RF_NOT_EMPT)
 		&& (dws->rx < dws->rx_end)) {
-		temp = dw_readw(dws, dr);
-		*(u16 *)(dws->rx) = temp;
-		dws->rx += 2;
+		rxw = dw_readw(dws, dr);
+		/* Care rx only if the transfer's original "rx" is not null */
+		if (dws->rx_end - dws->len) {
+			if (dws->n_bytes == 1)
+				*(u8 *)(dws->rx) = rxw;
+			else
+				*(u16 *)(dws->rx) = rxw;
+		}
+		dws->rx += dws->n_bytes;
 	}
 
 	wait_till_not_busy(dws);
@@ -383,8 +346,8 @@ static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 		left = (left > int_level) ? int_level : left;
 
 		while (left--)
-			dws->write(dws);
-		dws->read(dws);
+			dw_writer(dws);
+		dw_reader(dws);
 
 		/* Re-enable the IRQ if there is still data left to tx */
 		if (dws->tx_end > dws->tx)
@@ -417,13 +380,13 @@ static irqreturn_t dw_spi_irq(int irq, void *dev_id)
 /* Must be called inside pump_transfers() */
 static void poll_transfer(struct dw_spi *dws)
 {
-	while (dws->write(dws))
-		dws->read(dws);
+	while (dw_writer(dws))
+		dw_reader(dws);
 	/*
 	 * There is a possibility that the last word of a transaction
 	 * will be lost if data is not ready. Re-read to solve this issue.
 	 */
-	dws->read(dws);
+	dw_reader(dws);
 
 	dw_spi_xfer_done(dws);
 }
@@ -483,8 +446,6 @@ static void pump_transfers(unsigned long data)
 	dws->tx_end = dws->tx + transfer->len;
 	dws->rx = transfer->rx_buf;
 	dws->rx_end = dws->rx + transfer->len;
-	dws->write = dws->tx ? chip->write : null_writer;
-	dws->read = dws->rx ? chip->read : null_reader;
 	dws->cs_change = transfer->cs_change;
 	dws->len = dws->cur_transfer->len;
 	if (chip != dws->prev_chip)
@@ -520,18 +481,10 @@ static void pump_transfers(unsigned long data)
 		case 8:
 			dws->n_bytes = 1;
 			dws->dma_width = 1;
-			dws->read = (dws->read != null_reader) ?
-					u8_reader : null_reader;
-			dws->write = (dws->write != null_writer) ?
-					u8_writer : null_writer;
 			break;
 		case 16:
 			dws->n_bytes = 2;
 			dws->dma_width = 2;
-			dws->read = (dws->read != null_reader) ?
-					u16_reader : null_reader;
-			dws->write = (dws->write != null_writer) ?
-					u16_writer : null_writer;
 			break;
 		default:
 			printk(KERN_ERR "MRST SPI0: unsupported bits:"
@@ -733,13 +686,9 @@ static int dw_spi_setup(struct spi_device *spi)
 	if (spi->bits_per_word <= 8) {
 		chip->n_bytes = 1;
 		chip->dma_width = 1;
-		chip->read = u8_reader;
-		chip->write = u8_writer;
 	} else if (spi->bits_per_word <= 16) {
 		chip->n_bytes = 2;
 		chip->dma_width = 2;
-		chip->read = u16_reader;
-		chip->write = u16_writer;
 	} else {
 		/* Never take >16b case for MRST SPIC */
 		dev_err(&spi->dev, "invalid wordsize\n");

drivers/spi/dw_spi.h

@@ -137,8 +137,6 @@ struct dw_spi {
 	u8			max_bits_per_word;	/* maxim is 16b */
 	u32			dma_width;
 	int			cs_change;
-	int			(*write)(struct dw_spi *dws);
-	int			(*read)(struct dw_spi *dws);
 	irqreturn_t		(*transfer_handler)(struct dw_spi *dws);
 	void			(*cs_control)(u32 command);