spi/bcm63xx-hsspi: add support for dual spi read/write

Add support for dual read/writes on spi-bcm63xx-hsspi. This has been
tested with a s25fl129p1 dual read capable spi flash, with a nice speed
improvement:

serial read:

root@OpenWrt:/# time dd if=/dev/mtd4 of=/dev/null bs=8192
2032+0 records in
2032+0 records out
real    0m 4.39s
user    0m 0.00s
sys     0m 1.55s

dual read:

root@OpenWrt:/# time dd if=/dev/mtd4 of=/dev/null bs=8192
2032+0 records in
2032+0 records out
real    0m 3.09s
user    0m 0.00s
sys     0m 1.56s
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm63xx-hsspi.c

@@ -76,6 +76,7 @@
 #define HSSPI_FIFO_REG(x)			(0x200 + (x) * 0x200)
 
 
+#define HSSPI_OP_MULTIBIT			BIT(11)
 #define HSSPI_OP_CODE_SHIFT			13
 #define HSSPI_OP_SLEEP				(0 << HSSPI_OP_CODE_SHIFT)
 #define HSSPI_OP_READ_WRITE			(1 << HSSPI_OP_CODE_SHIFT)
@@ -171,9 +172,12 @@ static int bcm63xx_hsspi_do_txrx(struct spi_device *spi, struct spi_transfer *t)
 	if (opcode != HSSPI_OP_READ)
 		step_size -= HSSPI_OPCODE_LEN;
 
-	__raw_writel(0 << MODE_CTRL_PREPENDBYTE_CNT_SHIFT |
-		     2 << MODE_CTRL_MULTIDATA_WR_STRT_SHIFT |
-		     2 << MODE_CTRL_MULTIDATA_RD_STRT_SHIFT | 0xff,
+	if ((opcode == HSSPI_OP_READ && t->rx_nbits == SPI_NBITS_DUAL) ||
+	    (opcode == HSSPI_OP_WRITE && t->tx_nbits == SPI_NBITS_DUAL))
+		opcode |= HSSPI_OP_MULTIBIT;
+
+	__raw_writel(1 << MODE_CTRL_MULTIDATA_WR_SIZE_SHIFT |
+		     1 << MODE_CTRL_MULTIDATA_RD_SIZE_SHIFT | 0xff,
 		     bs->regs + HSSPI_PROFILE_MODE_CTRL_REG(chip_select));
 
 	while (pending > 0) {
@@ -374,7 +378,8 @@ static int bcm63xx_hsspi_probe(struct platform_device *pdev)
 	master->num_chipselect = 8;
 	master->setup = bcm63xx_hsspi_setup;
 	master->transfer_one_message = bcm63xx_hsspi_transfer_one;
-	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH |
+			    SPI_RX_DUAL | SPI_TX_DUAL;
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
 	master->auto_runtime_pm = true;