diff options
| author | Serge Semin | 2019-04-26 13:30:07 +0300 |
|---|---|---|
| committer | Mark Brown | 2019-05-02 10:38:00 +0900 |
| commit | d61ad23cb3be09ff4956e9b9794134456522817f (patch) | |
| tree | 20f0633d03bb704571d4abaeacb37f9f60bc1bb4 /drivers/spi | |
| parent | 1dfbf334f12361ebe6269c5918328b755ee960c7 (diff) | |
spi: Clear SPI_CS_HIGH flag from bad_bits for GPIO chip-select
When GPIO chip-select is used nothing prevents any available SPI
controllers to work with both CS-high and traditional CS-low modes.
In fact the SPI bus core code already does it, so we don't need to
introduce any modification there. But spi_setup() still fails to
switch the interface settings if CS-high flag is set for the case
of GPIO-driven slave chip-select when the SPI controller doesn't
support the hardwired CS-inversion. Lets fix it by clearing the
SPI_CS_HIGH flag out from bad_bits (unsupported by controller) when
client chip is selected by GPIO.
This feature is useful for slave devices, which in accordance with
communication protocol can work with both active-high and active-low
chip-selects. I am aware of one such device. It is MMC-SPI interface,
when at init sequence the driver needs to perform a read operation with
low and high chip-select sequentially (requirement of 74 clock cycles
with both chipselect, see the mmc_spi driver for details).
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 2195fa265aef..5e75944ad5d1 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2945,6 +2945,11 @@ int spi_setup(struct spi_device *spi) * so it is ignored here. */ bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD); + /* nothing prevents from working with active-high CS in case if it + * is driven by GPIO. + */ + if (gpio_is_valid(spi->cs_gpio)) + bad_bits &= ~SPI_CS_HIGH; ugly_bits = bad_bits & (SPI_TX_DUAL | SPI_TX_QUAD | SPI_TX_OCTAL | SPI_RX_DUAL | SPI_RX_QUAD | SPI_RX_OCTAL); |