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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>
This commit is contained in:
Rasmus Villemoes 2020-02-11 15:20:25 +00:00 committed by Tom Rini
parent 391c40048b
commit 4856cc7a97
1 changed files with 53 additions and 11 deletions
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64
drivers/spi/mpc8xxx_spi.c
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@ -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;
}