diff options
| -rw-r--r-- | drivers/spi/spi-cadence.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c index bb758978465d..f55702937052 100644 --- a/drivers/spi/spi-cadence.c +++ b/drivers/spi/spi-cadence.c @@ -205,18 +205,30 @@ static void cdns_spi_chipselect(struct spi_device *spi, bool is_high) static void cdns_spi_config_clock_mode(struct spi_device *spi) { struct cdns_spi *xspi = spi_master_get_devdata(spi->master); - u32 ctrl_reg; + u32 ctrl_reg, new_ctrl_reg; - ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET); + new_ctrl_reg = ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET); /* Set the SPI clock phase and clock polarity */ - ctrl_reg &= ~(CDNS_SPI_CR_CPHA_MASK | CDNS_SPI_CR_CPOL_MASK); + new_ctrl_reg &= ~(CDNS_SPI_CR_CPHA_MASK | CDNS_SPI_CR_CPOL_MASK); if (spi->mode & SPI_CPHA) - ctrl_reg |= CDNS_SPI_CR_CPHA_MASK; + new_ctrl_reg |= CDNS_SPI_CR_CPHA_MASK; if (spi->mode & SPI_CPOL) - ctrl_reg |= CDNS_SPI_CR_CPOL_MASK; - - cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, ctrl_reg); + new_ctrl_reg |= CDNS_SPI_CR_CPOL_MASK; + + if (new_ctrl_reg != ctrl_reg) { + /* + * Just writing the CR register does not seem to apply the clock + * setting changes. This is problematic when changing the clock + * polarity as it will cause the SPI slave to see spurious clock + * transitions. To workaround the issue toggle the ER register. + */ + cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET, + CDNS_SPI_ER_DISABLE_MASK); + cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, new_ctrl_reg); + cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET, + CDNS_SPI_ER_ENABLE_MASK); + } } /** |