Use the oscillator as the source clock when we cannot achieve a low-enough speed with the peripheral clock. This happens when we request 3MHz on a SPI clock, for example.
Signed-off-by: Simon Glass sjg@chromium.org ---
drivers/spi/tegra114_spi.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/spi/tegra114_spi.c b/drivers/spi/tegra114_spi.c index a73c6b0..1c5368b 100644 --- a/drivers/spi/tegra114_spi.c +++ b/drivers/spi/tegra114_spi.c @@ -143,6 +143,7 @@ static int tegra114_spi_probe(struct udevice *bus) { struct tegra_spi_platdata *plat = dev_get_platdata(bus); struct tegra114_spi_priv *priv = dev_get_priv(bus); + ulong rate;
priv->regs = (struct spi_regs *)plat->base;
@@ -150,9 +151,20 @@ static int tegra114_spi_probe(struct udevice *bus) priv->freq = plat->frequency; priv->periph_id = plat->periph_id;
- /* Change SPI clock to correct frequency, PLLP_OUT0 source */ - clock_start_periph_pll(priv->periph_id, CLOCK_ID_PERIPH, - priv->freq); + /* + * Change SPI clock to correct frequency, PLLP_OUT0 source, falling + * back to the oscillator if that is too fast. + */ + rate = clock_start_periph_pll(priv->periph_id, CLOCK_ID_PERIPH, + priv->freq); + if (rate > priv->freq + 100000) { + rate = clock_start_periph_pll(priv->periph_id, CLOCK_ID_OSC, + priv->freq); + if (rate != priv->freq) { + printf("Warning: SPI '%s' requested clock %u, actual clock %lu\n", + bus->name, priv->freq, rate); + } + }
setbits_le32(&priv->regs->command1, SPI_CMD1_M_S | SPI_CMD1_CS_SW_HW | (priv->mode << SPI_CMD1_MODE_SHIFT) | SPI_CMD1_CS_SW_VAL);