[PATCH] dm: spi: fix CPHA and implement CPOL for soft-spi

[J. Holland]

Implement SPI modes for CPOL/CPHA in the soft-spi driver. Previously, 
CPOL=1 was
hard-coded and CPHA was implemented inversely (defaulting to CPHA=1).

Signed-off-by: Johannes Holland <joh.ho at gmx.de>
---
  drivers/spi/soft_spi.c | 56 ++++++++++++++++++++++++++++++++----------
  1 file changed, 43 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/soft_spi.c b/drivers/spi/soft_spi.c
index b80f810bd1..5932ce8c5c 100644
--- a/drivers/spi/soft_spi.c
+++ b/drivers/spi/soft_spi.c
@@ -58,10 +58,12 @@ 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;
@@ -79,11 +81,14 @@ 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)
@@ -114,15 +119,18 @@ 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",
            dev->parent->name, dev->name, *(uint *)txd, *(uint *)rxd,
            bitlen);

-    if (flags & SPI_XFER_BEGIN)
+    if (flags & SPI_XFER_BEGIN) {
          soft_spi_cs_activate(dev);
+        udelay(plat->spi_delay_us);
+    }

      for (j = 0; j < bitlen; j++) {
          /*
@@ -140,22 +148,42 @@ 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
@@ -168,15 +196,17 @@ static int soft_spi_xfer(struct udevice *dev, 
unsigned int bitlen,
          *rxd++ = tmpdin;
      }

-    if (flags & SPI_XFER_END)
+    if (flags & SPI_XFER_END) {
+        udelay(plat->spi_delay_us);
          soft_spi_cs_deactivate(dev);
+    }

      return 0;
  }

  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;
  }

--
2.26.0