Reduce the number of reads per byte transferred on the BUF register from 2 to 1 and take advantage of the TX buffer in the SPI module.
Signed-off-by: Delio Brignoli dbrignoli@audioscience.com --- drivers/spi/davinci_spi.c | 67 +++++++++++++++++++++++--------------------- 1 files changed, 35 insertions(+), 32 deletions(-)
diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c index 60ba007..b4a74de 100644 --- a/drivers/spi/davinci_spi.c +++ b/drivers/spi/davinci_spi.c @@ -131,6 +131,7 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, { struct davinci_spi_slave *ds = to_davinci_spi(slave); unsigned int len, data1_reg_val = readl(&ds->regs->dat1); + unsigned int i_cnt = 0, o_cnt = 0, buf_reg_val; int ret, i; const u8 *txp = dout; /* dout can be NULL for read operation */ u8 *rxp = din; /* din can be NULL for write operation */ @@ -159,41 +160,43 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, readl(&ds->regs->buf);
/* keep writing and reading 1 byte until done */ - for (i = 0; i < len; i++) { - /* wait till TXFULL is asserted */ - while (readl(&ds->regs->buf) & SPIBUF_TXFULL_MASK); - - /* write the data */ - data1_reg_val &= ~0xFFFF; - if (txp) { - data1_reg_val |= *txp; - txp++; + while((i_cnt < len) || (o_cnt < len)) { + /* read RX buffer and flags */ + buf_reg_val = readl(&ds->regs->buf); + + /* if data is available */ + if ((i_cnt < len) && (buf_reg_val & SPIBUF_RXEMPTY_MASK) == 0) { + /* if there is no read buffer simply ignore the read character */ + if(rxp) { + *rxp = buf_reg_val & 0xFF; + rxp++; + } + /* increment read words count */ + i_cnt++; }
- /* - * Write to DAT1 is required to keep the serial transfer going. - * We just terminate when we reach the end. - */ - if ((i == (len - 1)) && (flags & SPI_XFER_END)) { - /* clear CS hold */ - writel(data1_reg_val & - ~(1 << SPIDAT1_CSHOLD_SHIFT), &ds->regs->dat1); - } else { - /* enable CS hold */ - data1_reg_val |= ((1 << SPIDAT1_CSHOLD_SHIFT) | + /* if the tx buffer is empty and there is still data to transmit */ + if ((o_cnt < len) && ((buf_reg_val & SPIBUF_TXFULL_MASK) == 0)) { + /* write the data */ + data1_reg_val &= ~0xFFFF; + if(txp) { + data1_reg_val |= *txp; + txp++; + } + /* write to DAT1 is required to keep the serial transfer going */ + /* we just terminate when we reach the end */ + if((o_cnt == (len -1)) && (flags & SPI_XFER_END)) { + /* clear CS hold */ + writel(data1_reg_val & + ~(1 << SPIDAT1_CSHOLD_SHIFT), &ds->regs->dat1); + } else { + /* enable CS hold and write TX register */ + data1_reg_val |= ((1 << SPIDAT1_CSHOLD_SHIFT) | (slave->cs << SPIDAT1_CSNR_SHIFT)); - writel(data1_reg_val, &ds->regs->dat1); - } - - /* read the data - wait for data availability */ - while (readl(&ds->regs->buf) & SPIBUF_RXEMPTY_MASK); - - if (rxp) { - *rxp = readl(&ds->regs->buf) & 0xFF; - rxp++; - } else { - /* simply drop the read character */ - readl(&ds->regs->buf); + writel(data1_reg_val, &ds->regs->dat1); + } + /* increment written words count */ + o_cnt++; } } return 0;