On Wed, Mar 12, 2014 at 16:20 +0100, Michael Grzeschik wrote: > > The bitbang spi driver currently only supports the MSB mode. This patch > adds the possibility to clock the data in LSB mode. > > Signed-off-by: Michael Grzeschik <[email protected]> > --- > drivers/spi/spi-bitbang-txrx.h | 98 > +++++++++++++++++++++++++++++------------- > drivers/spi/spi-bitbang.c | 3 +- > 2 files changed, 71 insertions(+), 30 deletions(-) > > diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h > index b6e348d..7f9c020 100644 > --- a/drivers/spi/spi-bitbang-txrx.h > +++ b/drivers/spi/spi-bitbang-txrx.h > @@ -49,22 +49,42 @@ bitbang_txrx_be_cpha0(struct spi_device *spi, > { > /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ > > - /* clock starts at inactive polarity */ > - for (word <<= (32 - bits); likely(bits); bits--) { > - > - /* setup MSB (to slave) on trailing edge */ > - if ((flags & SPI_MASTER_NO_TX) == 0) > - setmosi(spi, word & (1 << 31)); > - spidelay(nsecs); /* T(setup) */ > - > - setsck(spi, !cpol); > - spidelay(nsecs); > - > - /* sample MSB (from slave) on leading edge */ > - if ((flags & SPI_MASTER_NO_RX) == 0) > - word |= getmiso(spi); > - setsck(spi, cpol); > - word <<= 1; > + if (spi->mode & SPI_LSB_FIRST) { > + /* clock starts at inactive polarity */ > + for (; likely(bits); bits--) { > + > + /* setup MSB (to slave) on trailing edge */ > + if ((flags & SPI_MASTER_NO_TX) == 0) > + setmosi(spi, word & 1); > + spidelay(nsecs); /* T(setup) */ > + > + setsck(spi, !cpol); > + spidelay(nsecs); > + > + /* sample LSB (from slave) on leading edge */ > + if ((flags & SPI_MASTER_NO_RX) == 0) > + word |= getmiso(spi); > + setsck(spi, cpol); > + word >>= 1; > + } > + } else { > + /* clock starts at inactive polarity */ > + for (word <<= (32 - bits); likely(bits); bits--) { > + > + /* setup MSB (to slave) on trailing edge */ > + if ((flags & SPI_MASTER_NO_TX) == 0) > + setmosi(spi, word & (1 << 31)); > + spidelay(nsecs); /* T(setup) */ > + > + setsck(spi, !cpol); > + spidelay(nsecs); > + > + /* sample MSB (from slave) on leading edge */ > + if ((flags & SPI_MASTER_NO_RX) == 0) > + word |= getmiso(spi); > + setsck(spi, cpol); > + word <<= 1; > + } > } > return word; > }
Would it be useful to not duplicate the transmission logic, but instead to optionally "bit swap" the TX and RX data before and after the common transmission logic? Just a though whether this might help maintenance. There might even be existing and proven code to bit swap integers? virtually yours Gerhard Sittig -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr. 5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
