diff options
| author | Martin Sperl <kernel@martin.sperl.org> | 2015-07-28 14:03:12 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-09-21 10:05:34 -0700 |
| commit | 7f3f69a695fe2d10a9afad4419c68d731f775b94 (patch) | |
| tree | d41932543818f455d9e786795b7ba2dddc0fcd3d /drivers/spi | |
| parent | a1ff8fe3a5387ac0c33b2a4677690e322bec8c04 (diff) | |
spi: bcm2835: set up spi-mode before asserting cs-gpio
commit acace73df2c1913a526c1b41e4741a4a6704c863 upstream.
When using reverse polarity for clock (spi-cpol) on a device
the clock line gets altered after chip-select has been asserted
resulting in an additional clock beat, which confuses hardware.
This did not show when using native-CS, as the same register
is used to control cs as well as polarity, so the changes came
into effect at the same time. Unfortunately this is not true
with gpio-cs.
To avoid this situation this patch moves the setup of polarity
(spi-cpol and spi-cpha) outside of the chip-select into
prepare_message, which is run prior to asserting chip-select.
Also fixes resetting 3-wire mode after use of rx-mode, so that
a 3-Wire sequence TX, RX, TX works as well (right now it runs
TX, RX, RX instead)
Reported-by: Noralf Tronnes <noralf@tronnes.org>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-bcm2835.c | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 37875cf942f7..a5067739ee93 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -257,13 +257,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536); bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); - /* handle all the modes */ + /* handle all the 3-wire mode */ if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf)) cs |= BCM2835_SPI_CS_REN; - if (spi->mode & SPI_CPOL) - cs |= BCM2835_SPI_CS_CPOL; - if (spi->mode & SPI_CPHA) - cs |= BCM2835_SPI_CS_CPHA; + else + cs &= ~BCM2835_SPI_CS_REN; /* for gpio_cs set dummy CS so that no HW-CS get changed * we can not run this in bcm2835_spi_set_cs, as it does @@ -291,6 +289,25 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs); } +static int bcm2835_spi_prepare_message(struct spi_master *master, + struct spi_message *msg) +{ + struct spi_device *spi = msg->spi; + struct bcm2835_spi *bs = spi_master_get_devdata(master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA); + + if (spi->mode & SPI_CPOL) + cs |= BCM2835_SPI_CS_CPOL; + if (spi->mode & SPI_CPHA) + cs |= BCM2835_SPI_CS_CPHA; + + bcm2835_wr(bs, BCM2835_SPI_CS, cs); + + return 0; +} + static void bcm2835_spi_handle_err(struct spi_master *master, struct spi_message *msg) { @@ -429,6 +446,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) master->set_cs = bcm2835_spi_set_cs; master->transfer_one = bcm2835_spi_transfer_one; master->handle_err = bcm2835_spi_handle_err; + master->prepare_message = bcm2835_spi_prepare_message; master->dev.of_node = pdev->dev.of_node; bs = spi_master_get_devdata(master); |