net: dsa: microchip: Factor out register access opcode generation

/* Enough to read all switch port registers. */

#define SPI_TX_BUF_LEN			0x100

static int ksz9477_spi_read_reg(struct spi_device *spi, u32 reg, u8 *val,

				unsigned int len)

static u32 ksz9477_spi_cmd(u32 reg, bool read)

{

	u32 txbuf;

	int ret;

	txbuf = reg & SPI_ADDR_MASK;

	txbuf |= KS_SPIOP_RD << SPI_ADDR_SHIFT;

	txbuf |= (read ? KS_SPIOP_RD : KS_SPIOP_WR) << SPI_ADDR_SHIFT;

	txbuf <<= SPI_TURNAROUND_SHIFT;

	txbuf = cpu_to_be32(txbuf);

	ret = spi_write_then_read(spi, &txbuf, 4, val, len);

	return ret;

	return txbuf;

}

static int ksz9477_spi_read_reg(struct spi_device *spi, u32 reg, u8 *val,

				unsigned int len)

{

	u32 txbuf = ksz9477_spi_cmd(reg, true);

	return spi_write_then_read(spi, &txbuf, 4, val, len);

}

static int ksz9477_spi_write_reg(struct spi_device *spi, u32 reg, u8 *val,

{

	u32 *txbuf = (u32 *)val;

	*txbuf = reg & SPI_ADDR_MASK;

	*txbuf |= (KS_SPIOP_WR << SPI_ADDR_SHIFT);

	*txbuf <<= SPI_TURNAROUND_SHIFT;

	*txbuf = cpu_to_be32(*txbuf);

	*txbuf = ksz9477_spi_cmd(reg, false);

	return spi_write(spi, txbuf, 4 + len);

}