From 1847e3046c528bd85bd51e2860f4139bd9052d6c Mon Sep 17 00:00:00 2001 From: Andreas Färber Date: Sat, 19 Feb 2022 14:15:48 +0100 Subject: spi: gpio: Implement LSB First bitbang support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add support for slave DT property spi-lsb-first, i.e., SPI_LSB_FIRST mode. Duplicate the inline helpers bitbang_txrx_be_cpha{0,1} as LE versions. Conditionally call them from all the spi-gpio txrx_word callbacks. Some alternatives to this implementation approach were discussed back then [0], but eventually it was considered reasonable. [0] https://lore.kernel.org/linux-arm-kernel/20191212033952.5967-8-afaerber@suse.de/ Signed-off-by: Andreas Färber Signed-off-by: Heiner Kallweit Tested-by: Christian Hewitt Link: https://lore.kernel.org/r/feac3377-4ad1-77d8-9a18-3588d80fb909@gmail.com Signed-off-by: Mark Brown --- drivers/spi/spi-bitbang-txrx.h | 66 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) (limited to 'drivers/spi/spi-bitbang-txrx.h') diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h index ae61d72c7d28..267342dfa738 100644 --- a/drivers/spi/spi-bitbang-txrx.h +++ b/drivers/spi/spi-bitbang-txrx.h @@ -41,6 +41,8 @@ * chips need ... there may be several reasons you'd need to tweak timings * in these routines, not just to make it faster or slower to match a * particular CPU clock rate. + * + * ToDo: Maybe the bitrev macros can be used to improve the code? */ static inline u32 @@ -106,3 +108,67 @@ bitbang_txrx_be_cpha1(struct spi_device *spi, } return word; } + +static inline u32 +bitbang_txrx_le_cpha0(struct spi_device *spi, + unsigned int nsecs, unsigned int cpol, unsigned int flags, + u32 word, u8 bits) +{ + /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ + + u32 oldbit = !(word & 1); + /* clock starts at inactive polarity */ + for (; likely(bits); bits--) { + + /* setup LSB (to slave) on trailing edge */ + if ((flags & SPI_MASTER_NO_TX) == 0) { + if ((word & 1) != oldbit) { + setmosi(spi, word & 1); + oldbit = word & 1; + } + } + spidelay(nsecs); /* T(setup) */ + + setsck(spi, !cpol); + spidelay(nsecs); + + /* sample LSB (from slave) on leading edge */ + word >>= 1; + if ((flags & SPI_MASTER_NO_RX) == 0) + word |= getmiso(spi) << (bits - 1); + setsck(spi, cpol); + } + return word; +} + +static inline u32 +bitbang_txrx_le_cpha1(struct spi_device *spi, + unsigned int nsecs, unsigned int cpol, unsigned int flags, + u32 word, u8 bits) +{ + /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */ + + u32 oldbit = !(word & 1); + /* clock starts at inactive polarity */ + for (; likely(bits); bits--) { + + /* setup LSB (to slave) on leading edge */ + setsck(spi, !cpol); + if ((flags & SPI_MASTER_NO_TX) == 0) { + if ((word & 1) != oldbit) { + setmosi(spi, word & 1); + oldbit = word & 1; + } + } + spidelay(nsecs); /* T(setup) */ + + setsck(spi, cpol); + spidelay(nsecs); + + /* sample LSB (from slave) on trailing edge */ + word >>= 1; + if ((flags & SPI_MASTER_NO_RX) == 0) + word |= getmiso(spi) << (bits - 1); + } + return word; +} -- cgit v1.2.3