MX28: SPI: Refactor spi_xfer a bit

This makes it easier to adapt for addition of DMA support.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Wolfgang Denk <wd@denx.de>

diff --git a/drivers/spi/mxs_spi.c b/drivers/spi/mxs_spi.c
index 7859536..a21b02b 100644 (file)
--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -146,21 +146,33 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
        struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
        struct mx28_ssp_regs *ssp_regs = mxs_slave->regs;
        int len = bitlen / 8;
-       const char *tx = dout;
-       char *rx = din;
        char dummy;
+       int write = 0;
+       char *data = NULL;
 
        if (bitlen == 0) {
                if (flags & SPI_XFER_END) {
-                       rx = &dummy;
+                       din = (void *)&dummy;
                        len = 1;
                } else
                        return 0;
        }
 
-       if (!rx && !tx)
+       /* Half-duplex only */
+       if (din && dout)
+               return -EINVAL;
+       /* No data */
+       if (!din && !dout)
                return 0;
 
+       if (dout) {
+               data = (char *)dout;
+               write = 1;
+       } else if (din) {
+               data = (char *)din;
+               write = 0;
+       }
+
        if (flags & SPI_XFER_BEGIN)
                mxs_spi_start_xfer(ssp_regs);
 
@@ -171,7 +183,7 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
                if ((flags & SPI_XFER_END) && !len)
                        mxs_spi_end_xfer(ssp_regs);
 
-               if (tx)
+               if (write)
                        writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_clr);
                else
                        writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_set);
@@ -184,20 +196,20 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
                        return -ETIMEDOUT;
                }
 
-               if (tx)
-                       writel(*tx++, &ssp_regs->hw_ssp_data);
+               if (write)
+                       writel(*data++, &ssp_regs->hw_ssp_data);
 
                writel(SSP_CTRL0_DATA_XFER, &ssp_regs->hw_ssp_ctrl0_set);
 
-               if (rx) {
+               if (!write) {
                        if (mx28_wait_mask_clr(&ssp_regs->hw_ssp_status_reg,
                                SSP_STATUS_FIFO_EMPTY, MXS_SPI_MAX_TIMEOUT)) {
                                printf("MXS SPI: Timeout waiting for data\n");
                                return -ETIMEDOUT;
                        }
 
-                       *rx = readl(&ssp_regs->hw_ssp_data);
-                       rx++;
+                       *data = readl(&ssp_regs->hw_ssp_data);
+                       data++;
                }
 
                if (mx28_wait_mask_clr(&ssp_regs->hw_ssp_ctrl0_reg,