From: Martin Sperl <[email protected]> use cs-gpios for the spi bus master and standard gpio operation instead of relying on the HW with just 2 chip_selects.
Signed-off-by: Martin Sperl <[email protected]> --- drivers/spi/spi-bcm2835.c | 65 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 58 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index e1dea40..5fbad64 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -30,6 +30,7 @@ #include <linux/of.h> #include <linux/of_irq.h> #include <linux/of_device.h> +#include <linux/of_gpio.h> #include <linux/spi/spi.h> /* SPI register offsets */ @@ -116,6 +117,16 @@ static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len) } } +/* ideally spi_set_cs would be exported by spi-core */ +static inline void bcm2835_set_cs(struct spi_device *spi, bool enable) +{ + if (spi->mode & SPI_CS_HIGH) + enable = !enable; + + if (gpio_is_valid(spi->cs_gpio)) + gpio_set_value(spi->cs_gpio, !enable); +} + static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id) { struct spi_master *master = dev_id; @@ -207,12 +218,24 @@ static int bcm2835_spi_start_transfer( cs |= BCM2835_SPI_CS_CPHA; if (!(spi->mode & SPI_NO_CS)) { - if (spi->mode & SPI_CS_HIGH) { - cs |= BCM2835_SPI_CS_CSPOL; - cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select; - } + if (gpio_is_valid(spi->cs_gpio)) { + bcm2835_set_cs(spi, 1); + } else { + /* Legacy mode using HW chip selects + * note that there is a bug in this when there are + * multiple devices on the bus with at least one + * having SPI_CS_HIGH set - the other CS_CSPOLX get + * reset to 0 when any other device starts a transfer + * this is due to a shared register for the polarity + */ + if (spi->mode & SPI_CS_HIGH) { + cs |= BCM2835_SPI_CS_CSPOL; + cs |= BCM2835_SPI_CS_CSPOL0 + << spi->chip_select; + } - cs |= spi->chip_select; + cs |= spi->chip_select; + } } reinit_completion(&bs->done); @@ -248,9 +271,12 @@ static int bcm2835_spi_finish_transfer( if (tfr->delay_usecs) udelay(tfr->delay_usecs); - if (cs_change) + if (cs_change) { + /* reset CS */ + bcm2835_set_cs(spi, 0); /* Clear TA flag */ bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA); + } return 0; } @@ -290,15 +316,39 @@ static int bcm2835_spi_transfer_one( } out: - /* Clear FIFOs, and disable the HW block */ + /* Clear FIFOs, reset CS and disable the HW block */ bcm2835_wr(bs, BCM2835_SPI_CS, BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); + bcm2835_set_cs(spi, 0); mesg->status = err; spi_finalize_current_message(master); return 0; } +static int bcm2835_spi_setup(struct spi_device *spi) +{ + /* do not care when in SPI_NO_CS mode */ + if (spi->mode & SPI_NO_CS) + return 0; + + /* setting up CS right from the start */ + if (gpio_is_valid(spi->cs_gpio)) { + bcm2835_set_cs(spi, 0); + return 0; + } + + /* Legacy mode using HW chipselects */ + if (spi->chip_select > 2) { + dev_err(&spi->dev, + "setup: only three native chip-selects are supported\n" + ); + return -EINVAL; + } + + return 0; +} + static int bcm2835_spi_probe(struct platform_device *pdev) { struct spi_master *master; @@ -318,6 +368,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) master->bits_per_word_mask = SPI_BPW_MASK(8); master->num_chipselect = 3; master->transfer_one_message = bcm2835_spi_transfer_one; + master->setup = bcm2835_spi_setup; master->dev.of_node = pdev->dev.of_node; bs = spi_master_get_devdata(master); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
