spi: fsl-espi: fix support for all available clock rates
According to NXP ESPI datasheet, the SPI clock rate is:
spi_clk = System_Clock / ( 2 * DIV16 * ( 1 + PM ) )
Where System_Clock is the platform clock divided by 2,
DIV16 may be 1 or 16, and PM is a 4 bits integer (0 to 15).
Isolating PM on the expression, we get:
PM = (System_Clock / ( 2 * DIV16 * spi_clk ) ) - 1
Where System_Clock = mpc8xxx_spi->spibrg / 2, spi_clk = hz,
and DIV16 = 1 or DIV16 = 16. So,
PM = (mpc8xxx_spi->spibrg / ( 4 * hz) ) - 1
or
PM = (mpc8xxx_spi->spibrg / ( 16 * 4 * hz) ) - 1
Current spi-fsl-espi driver can't configure the HW for all
supported clock rates. It filters out clock rates for PM = 0
and PM = 1.
This patch allows all range of supported clock rates to be
configured on the ESPI controller.
Signed-off-by: Paulo Zaneti <paulo.zaneti@datacom.ind.br>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 1d3c902..8b3a287 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c
@@ -247,8 +247,7 @@
{
struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(spi->master);
int bits_per_word = t ? t->bits_per_word : spi->bits_per_word;
- u32 hz = t ? t->speed_hz : spi->max_speed_hz;
- u8 pm;
+ u32 pm, hz = t ? t->speed_hz : spi->max_speed_hz;
struct spi_mpc8xxx_cs *cs = spi->controller_state;
/* mask out bits we are going to set */
@@ -256,22 +255,19 @@
cs->hw_mode |= CSMODE_LEN(bits_per_word - 1);
- if ((mpc8xxx_spi->spibrg / hz) > 64) {
- cs->hw_mode |= CSMODE_DIV16;
- pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 16 * 4);
+ pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 4) - 1;
- WARN_ONCE(pm > 33, "%s: Requested speed is too low: %d Hz. "
- "Will use %d Hz instead.\n", dev_name(&spi->dev),
- hz, mpc8xxx_spi->spibrg / (4 * 16 * (32 + 1)));
- if (pm > 33)
- pm = 33;
- } else {
- pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 4);
+ if (pm > 15) {
+ cs->hw_mode |= CSMODE_DIV16;
+ pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 16 * 4) - 1;
+
+ WARN_ONCE(pm > 15,
+ "%s: Requested speed is too low: %u Hz. Will use %u Hz instead.\n",
+ dev_name(&spi->dev), hz,
+ mpc8xxx_spi->spibrg / (4 * 16 * (15 + 1)));
+ if (pm > 15)
+ pm = 15;
}
- if (pm)
- pm--;
- if (pm < 2)
- pm = 2;
cs->hw_mode |= CSMODE_PM(pm);