spi: add support for all spi modes with soft spi

The spi bitbanging driver did not implement all spi modes properly. Add
code to support all spi modes, honoring soft_spi_set_mode() and
defaulting to spi mode 0. Previously, CPHA was implemented inversely
(defaulting to CPHA=1) and CPOL=1 was hardcoded.

Signed-off-by: Johannes Holland <johannes.holland@infineon.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>

diff --git a/drivers/spi/soft_spi.c b/drivers/spi/soft_spi.c
index e8d7758..153bbf8 100644 (file)
--- a/drivers/spi/soft_spi.c
+++ b/drivers/spi/soft_spi.c
@@ -61,10 +61,12 @@ static int soft_spi_sda(struct udevice *dev, int bit)
 static int soft_spi_cs_activate(struct udevice *dev)
 {
        struct udevice *bus = dev_get_parent(dev);
+       struct soft_spi_priv *priv = dev_get_priv(bus);
        struct soft_spi_platdata *plat = dev_get_platdata(bus);
+       int cidle = !!(priv->mode & SPI_CPOL);
 
        dm_gpio_set_value(&plat->cs, 0);
-       dm_gpio_set_value(&plat->sclk, 0);
+       dm_gpio_set_value(&plat->sclk, cidle); /* to idle */
        dm_gpio_set_value(&plat->cs, 1);
 
        return 0;
@@ -82,11 +84,14 @@ static int soft_spi_cs_deactivate(struct udevice *dev)
 
 static int soft_spi_claim_bus(struct udevice *dev)
 {
+       struct udevice *bus = dev_get_parent(dev);
+       struct soft_spi_priv *priv = dev_get_priv(bus);
+       int cidle = !!(priv->mode & SPI_CPOL);
        /*
         * Make sure the SPI clock is in idle state as defined for
         * this slave.
         */
-       return soft_spi_scl(dev, 0);
+       return soft_spi_scl(dev, cidle);
 }
 
 static int soft_spi_release_bus(struct udevice *dev)
@@ -117,7 +122,8 @@ static int soft_spi_xfer(struct udevice *dev, unsigned int bitlen,
        uchar           tmpdout = 0;
        const u8        *txd = dout;
        u8              *rxd = din;
-       int             cpha = priv->mode & SPI_CPHA;
+       int             cpha = !!(priv->mode & SPI_CPHA);
+       int             cidle = !!(priv->mode & SPI_CPOL);
        unsigned int    j;
 
        debug("spi_xfer: slave %s:%s dout %08X din %08X bitlen %u\n",
@@ -143,22 +149,42 @@ static int soft_spi_xfer(struct udevice *dev, unsigned int bitlen,
                        tmpdin  = 0;
                }
 
-               if (!cpha)
-                       soft_spi_scl(dev, 0);
+               /*
+                * CPOL 0: idle is low (0), active is high (1)
+                * CPOL 1: idle is high (1), active is low (0)
+                */
+
+               /*
+                * drive bit
+                *  CPHA 1: CLK from idle to active
+                */
+               if (cpha)
+                       soft_spi_scl(dev, !cidle);
                if ((plat->flags & SPI_MASTER_NO_TX) == 0)
                        soft_spi_sda(dev, !!(tmpdout & 0x80));
                udelay(plat->spi_delay_us);
-               if (cpha)
-                       soft_spi_scl(dev, 0);
+
+               /*
+                * sample bit
+                *  CPHA 0: CLK from idle to active
+                *  CPHA 1: CLK from active to idle
+                */
+               if (!cpha)
+                       soft_spi_scl(dev, !cidle);
                else
-                       soft_spi_scl(dev, 1);
+                       soft_spi_scl(dev, cidle);
                tmpdin  <<= 1;
                if ((plat->flags & SPI_MASTER_NO_RX) == 0)
                        tmpdin  |= dm_gpio_get_value(&plat->miso);
                tmpdout <<= 1;
                udelay(plat->spi_delay_us);
-               if (cpha)
-                       soft_spi_scl(dev, 1);
+
+               /*
+                * drive bit
+                *  CPHA 0: CLK from active to idle
+                */
+               if (!cpha)
+                       soft_spi_scl(dev, cidle);
        }
        /*
         * If the number of bits isn't a multiple of 8, shift the last
@@ -179,7 +205,7 @@ static int soft_spi_xfer(struct udevice *dev, unsigned int bitlen,
 
 static int soft_spi_set_speed(struct udevice *dev, unsigned int speed)
 {
-       /* Accept any speed */
+       /* Ignore any speed settings. Speed is implemented via "spi-delay-us" */
        return 0;
 }