/* Selects the 16MHz oscilator on the HiFive1 board, which provides a clock
* that's accurate enough to actually drive serial ports off of.
*/
static int hifive1_clock_init(struct device *dev)
{
ARG_UNUSED(dev);
PRCI_REG(PRCI_PLLCFG) = PLL_REFSEL(1) | PLL_BYPASS(1);
PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
PRCI_REG(PRCI_HFROSCCFG) &= ~ROSC_EN(1);
return 0;
}
void
select_clock(const clock_config_t *cfg)
{
uint32_t new_qspi_div = 0;
uint32_t old_qspi_div = SPI0_REG(SPI_REG_SCKDIV);
/* Clock based on external escilator */
if (!cfg->xosc || cfg->pll) {
/* Turn on internal oscillator */
PRCI_REG(PRCI_HFROSCCFG) = ROSC_DIV(cfg->osc_div) |
ROSC_TRIM(MYNEWT_VAL(HFROSC_DEFAULT_TRIM_VAL)) |
ROSC_EN(1);
while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0) {
}
/* Compute CPU frequency on demand */
cpu_freq = 0;
}
if (cfg->xosc) {
/* Turn on external oscillator if not ready yet */
if ((PRCI_REG(PRCI_HFXOSCCFG) & XOSC_RDY(1)) == 0) {
PRCI_REG(PRCI_HFXOSCCFG) = XOSC_EN(1);
while ((PRCI_REG(PRCI_HFXOSCCFG) & XOSC_RDY(1)) == 0) {
}
}
cpu_freq = cfg->frq;
}
/*
* If reqested closk is higher then FLASH_MAX_CLOCK change divider so QSPI
* clock is in rage.
*/
if (cfg->frq >= MYNEWT_VAL(FLASH_MAX_CLOCK) * 2) {
new_qspi_div = (cfg->frq + MYNEWT_VAL(FLASH_MAX_CLOCK) - 1) / (2 * MYNEWT_VAL(FLASH_MAX_CLOCK)) - 1;
}
/* New qspi divider is higher, reduce qspi clock before switching to higher clock */
if (new_qspi_div > old_qspi_div) {
SPI0_REG(SPI_REG_SCKDIV) = new_qspi_div;
}
PRCI_REG(PRCI_PLLDIV) = PLL_FINAL_DIV_BY_1(cfg->pll_outdiv1) |
PLL_FINAL_DIV(cfg->pll_out_div);
if (cfg->pll) {
uint32_t now;
uint32_t pllcfg = PLL_REFSEL(cfg->xosc) |
PLL_R(cfg->pll_div_r) | PLL_F(cfg->pll_mul_f) | PLL_Q(cfg->pll_div_q);
PRCI_REG(PRCI_PLLCFG) = PLL_BYPASS(1) | pllcfg;
PRCI_REG(PRCI_PLLCFG) ^= PLL_BYPASS(1);
/* 100us lock grace period */
now = mtime_lo();
while (mtime_lo() - now < 4) {
}
/* Now it is safe to check for PLL Lock */
while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0) {
}
/* Select PLL as clock source */
PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1) | pllcfg;
} else {
/* Select bypassed PLL as source signal, it allows to use HFXOSC */
PRCI_REG(PRCI_PLLCFG) = PLL_BYPASS(1) | PLL_REFSEL(cfg->xosc) | PLL_SEL(1);
}
/*
* Old qspi divider was higher, now it's safe to reduce divider, increasing
* qspi clock for better performance
*/
if (new_qspi_div < old_qspi_div) {
SPI0_REG(SPI_REG_SCKDIV) = new_qspi_div;
}
}
void use_pll(int refsel, int bypass, int r, int f, int q)
{
// Ensure that we aren't running off the PLL before we mess with it.
if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
// Make sure the HFROSC is running at its default setting
use_hfrosc(4, 16);
}
// Set PLL Source to be HFXOSC if available.
uint32_t config_value = 0;
config_value |= PLL_REFSEL(refsel);
if (bypass) {
// Bypass
config_value |= PLL_BYPASS(1);
PRCI_REG(PRCI_PLLCFG) = config_value;
// If we don't have an HFXTAL, this doesn't really matter.
// Set our Final output divide to divide-by-1:
PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
} else {
// In case we are executing from QSPI,
// (which is quite likely) we need to
// set the QSPI clock divider appropriately
// before boosting the clock frequency.
// Div = f_sck/2
SPI0_REG(SPI_REG_SCKDIV) = 8;
// Set DIV Settings for PLL
// Both HFROSC and HFXOSC are modeled as ideal
// 16MHz sources (assuming dividers are set properly for
// HFROSC).
// (Legal values of f_REF are 6-48MHz)
// Set DIVR to divide-by-2 to get 8MHz frequency
// (legal values of f_R are 6-12 MHz)
config_value |= PLL_BYPASS(1);
config_value |= PLL_R(r);
// Set DIVF to get 512Mhz frequncy
// There is an implied multiply-by-2, 16Mhz.
// So need to write 32-1
// (legal values of f_F are 384-768 MHz)
config_value |= PLL_F(f);
// Set DIVQ to divide-by-2 to get 256 MHz frequency
// (legal values of f_Q are 50-400Mhz)
config_value |= PLL_Q(q);
// Set our Final output divide to divide-by-1:
PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
PRCI_REG(PRCI_PLLCFG) = config_value;
// Un-Bypass the PLL.
PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
// Wait for PLL Lock
// Note that the Lock signal can be glitchy.
// Need to wait 100 us
// RTC is running at 32kHz.
// So wait 4 ticks of RTC.
uint32_t now = mtime_lo();
while (mtime_lo() - now < 4) ;
// Now it is safe to check for PLL Lock
while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0) ;
}
// Switch over to PLL Clock source
PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
}