From f3e182c33e534f4caeb255a3ab927debc0d222aa Mon Sep 17 00:00:00 2001 From: Sowjanya Komatineni Date: Thu, 4 Apr 2019 17:14:02 -0700 Subject: spi: tegra114: de-assert CS before SPI mode change With SW CS, during the transfer completion CS is de-asserted by writing default command1 register value to SPI_COMMAND1 register. With this both mode and CS state are set at the same time and if current transfer mode is different to default SPI mode and if mode change happens prior to CS de-assert, clock polarity can change while CS is active before transfer finishes. This causes Slave to see spurious clock edges resulting in data mismatch. This patch fixes this by de-asserting CS before writing SPI_COMMAND1 to its default value so through out the transfer it will be in same SPI mode. Signed-off-by: Sowjanya Komatineni Signed-off-by: Mark Brown --- drivers/spi/spi-tegra114.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) (limited to 'drivers') diff --git a/drivers/spi/spi-tegra114.c b/drivers/spi/spi-tegra114.c index 09cfae3abce2..8de002fc6943 100644 --- a/drivers/spi/spi-tegra114.c +++ b/drivers/spi/spi-tegra114.c @@ -856,6 +856,19 @@ static void tegra_spi_transfer_delay(int delay) udelay(delay % 1000); } +static void tegra_spi_transfer_end(struct spi_device *spi) +{ + struct tegra_spi_data *tspi = spi_master_get_devdata(spi->master); + int cs_val = (spi->mode & SPI_CS_HIGH) ? 0 : 1; + + if (cs_val) + tspi->command1_reg |= SPI_CS_SW_VAL; + else + tspi->command1_reg &= ~SPI_CS_SW_VAL; + tegra_spi_writel(tspi, tspi->command1_reg, SPI_COMMAND1); + tegra_spi_writel(tspi, tspi->def_command1_reg, SPI_COMMAND1); +} + static int tegra_spi_transfer_one_message(struct spi_master *master, struct spi_message *msg) { @@ -918,8 +931,7 @@ static int tegra_spi_transfer_one_message(struct spi_master *master, complete_xfer: if (ret < 0 || skip) { - tegra_spi_writel(tspi, tspi->def_command1_reg, - SPI_COMMAND1); + tegra_spi_transfer_end(spi); tegra_spi_transfer_delay(xfer->delay_usecs); goto exit; } else if (list_is_last(&xfer->transfer_list, @@ -927,13 +939,11 @@ complete_xfer: if (xfer->cs_change) tspi->cs_control = spi; else { - tegra_spi_writel(tspi, tspi->def_command1_reg, - SPI_COMMAND1); + tegra_spi_transfer_end(spi); tegra_spi_transfer_delay(xfer->delay_usecs); } } else if (xfer->cs_change) { - tegra_spi_writel(tspi, tspi->def_command1_reg, - SPI_COMMAND1); + tegra_spi_transfer_end(spi); tegra_spi_transfer_delay(xfer->delay_usecs); } -- cgit v1.2.3