mpc8xxx_spi: implement real ->set_speed

Not all boards have the same CSB frequency, nor do every SPI slave
necessarily support running at 16.7 MHz. So implement ->set_speed;
that also allows using a smaller PM (i.e., 0) for slaves that do
support a higher speed.

Based on work by Klaus H. Sørensen.

Cc: Klaus H. Sorensen <khso@prevas.dk>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

diff --git a/drivers/spi/mpc8xxx_spi.c b/drivers/spi/mpc8xxx_spi.c
index 8ef24514112585b800cf551432c18aeea9d847a1..1bde31ad349f92485d45b7588f674f7e17f2e34e 100644 (file)
--- a/drivers/spi/mpc8xxx_spi.c
+++ b/drivers/spi/mpc8xxx_spi.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <clk.h>
 #include <dm.h>
 #include <errno.h>
 #include <malloc.h>
@@ -28,6 +29,7 @@ enum {
 
        SPI_MODE_LEN_MASK = 0xf00000,
        SPI_MODE_LEN_SHIFT = 20,
+       SPI_MODE_PM_SHIFT = 16,
        SPI_MODE_PM_MASK = 0xf0000,
 
        SPI_COM_LST = BIT(31 - 9),
@@ -37,24 +39,19 @@ struct mpc8xxx_priv {
        spi8xxx_t *spi;
        struct gpio_desc gpios[16];
        int cs_count;
+       ulong clk_rate;
 };
 
-static inline u32 to_prescale_mod(u32 val)
-{
-       return (min(val, (u32)15) << 16);
-}
-
 #define SPI_TIMEOUT    1000
 
 static int mpc8xxx_spi_ofdata_to_platdata(struct udevice *dev)
 {
        struct mpc8xxx_priv *priv = dev_get_priv(dev);
+       struct clk clk;
        int ret;
 
        priv->spi = (spi8xxx_t *)dev_read_addr(dev);
 
-       /* TODO(mario.six@gdsys.cc): Read clock and save the value */
-
        ret = gpio_request_list_by_name(dev, "gpios", priv->gpios,
                                        ARRAY_SIZE(priv->gpios), GPIOD_IS_OUT | GPIOD_ACTIVE_LOW);
        if (ret < 0)
@@ -62,6 +59,18 @@ static int mpc8xxx_spi_ofdata_to_platdata(struct udevice *dev)
 
        priv->cs_count = ret;
 
+       ret = clk_get_by_index(dev, 0, &clk);
+       if (ret) {
+               dev_err(dev, "%s: clock not defined\n", __func__);
+               return ret;
+       }
+
+       priv->clk_rate = clk_get_rate(&clk);
+       if (!priv->clk_rate) {
+               dev_err(dev, "%s: failed to get clock rate\n", __func__);
+               return -EINVAL;
+       }
+
        return 0;
 }
 
@@ -79,10 +88,6 @@ static int mpc8xxx_spi_probe(struct udevice *dev)
        /* set len to 8 bits */
        setbits_be32(&spi->mode, (8 - 1) << SPI_MODE_LEN_SHIFT);
 
-       /* TODO(mario.six@gdsys.cc): This only ever sets one fixed speed */
-       /* Use SYSCLK / 8 (16.67MHz typ.) */
-       clrsetbits_be32(&spi->mode, SPI_MODE_PM_MASK, to_prescale_mod(1));
-
        setbits_be32(&spi->mode, SPI_MODE_EN);
 
        /* Clear all SPI events */
@@ -204,6 +209,43 @@ static int mpc8xxx_spi_xfer(struct udevice *dev, uint bitlen,
 
 static int mpc8xxx_spi_set_speed(struct udevice *dev, uint speed)
 {
+       struct mpc8xxx_priv *priv = dev_get_priv(dev);
+       spi8xxx_t *spi = priv->spi;
+       u32 bits, mask, div16, pm;
+       u32 mode;
+       ulong clk;
+
+       clk = priv->clk_rate;
+       if (clk / 64 > speed) {
+               div16 = SPI_MODE_DIV16;
+               clk /= 16;
+       } else {
+               div16 = 0;
+       }
+       pm = (clk - 1)/(4*speed) + 1;
+       if (pm > 16) {
+               dev_err(dev, "requested speed %u too small\n", speed);
+               return -EINVAL;
+       }
+       pm--;
+
+       bits = div16 | (pm << SPI_MODE_PM_SHIFT);
+       mask = SPI_MODE_DIV16 | SPI_MODE_PM_MASK;
+       mode = in_be32(&spi->mode);
+       if ((mode & mask) != bits) {
+               /* Must clear mode[EN] while changing speed. */
+               mode &= ~(mask | SPI_MODE_EN);
+               out_be32(&spi->mode, mode);
+               mode |= bits;
+               out_be32(&spi->mode, mode);
+               mode |= SPI_MODE_EN;
+               out_be32(&spi->mode, mode);
+       }
+
+       debug("requested speed %u, set speed to %lu/(%s4*%u) == %lu\n",
+             speed, priv->clk_rate, div16 ? "16*" : "", pm + 1,
+             clk/(4*(pm + 1)));
+
        return 0;
 }