diff options
author | Andreas Färber <afaerber@suse.de> | 2022-02-19 14:15:48 +0100 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2022-02-22 11:56:41 +0000 |
commit | 1847e3046c528bd85bd51e2860f4139bd9052d6c (patch) | |
tree | b5384060b3dec3f43071d118d36185cf6f3fe9e5 | |
parent | 5741150c808b2bbeb1017609f3029daf6651b7d5 (diff) |
spi: gpio: Implement LSB First bitbang support
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 <afaerber@suse.de>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Christian Hewitt <christianshewitt@gmail.com>
Link: https://lore.kernel.org/r/feac3377-4ad1-77d8-9a18-3588d80fb909@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
-rw-r--r-- | drivers/spi/spi-bitbang-txrx.h | 66 | ||||
-rw-r--r-- | drivers/spi/spi-gpio.c | 42 |
2 files changed, 99 insertions, 9 deletions
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; +} diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c index 0584f4d2fde2..4b12c4964a66 100644 --- a/drivers/spi/spi-gpio.c +++ b/drivers/spi/spi-gpio.c @@ -135,25 +135,37 @@ static inline int getmiso(const struct spi_device *spi) static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { - return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha0(spi, nsecs, 0, flags, word, bits); + else + return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); } static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { - return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha1(spi, nsecs, 0, flags, word, bits); + else + return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); } static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { - return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha0(spi, nsecs, 1, flags, word, bits); + else + return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); } static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { - return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha1(spi, nsecs, 1, flags, word, bits); + else + return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); } /* @@ -170,28 +182,40 @@ static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { flags = spi->master->flags; - return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha0(spi, nsecs, 0, flags, word, bits); + else + return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); } static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { flags = spi->master->flags; - return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha1(spi, nsecs, 0, flags, word, bits); + else + return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); } static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { flags = spi->master->flags; - return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha0(spi, nsecs, 1, flags, word, bits); + else + return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); } static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { flags = spi->master->flags; - return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha1(spi, nsecs, 1, flags, word, bits); + else + return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); } /*----------------------------------------------------------------------*/ @@ -378,7 +402,7 @@ static int spi_gpio_probe(struct platform_device *pdev) master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); master->mode_bits = SPI_3WIRE | SPI_3WIRE_HIZ | SPI_CPHA | SPI_CPOL | - SPI_CS_HIGH; + SPI_CS_HIGH | SPI_LSB_FIRST; if (!spi_gpio->mosi) { /* HW configuration without MOSI pin * |