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// See LICENSE file for license details
#include "drivers/fe300prci/fe300prci_driver.h"
#include "platform.h"
#include <unistd.h>
#define rdmcycle(x) { \
uint32_t lo, hi, hi2; \
__asm__ __volatile__ ("1:\n\t" \
"csrr %0, mcycleh\n\t" \
"csrr %1, mcycle\n\t" \
"csrr %2, mcycleh\n\t" \
"bne %0, %2, 1b\n\t" \
: "=r" (hi), "=r" (lo), "=r" (hi2)) ; \
*(x) = lo | ((uint64_t) hi << 32); \
}
static uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq)
{
uint32_t start_mtime = CLINT_REG(CLINT_MTIME);
uint32_t end_mtime = start_mtime + mtime_ticks + 1;
// Make sure we won't get rollover.
while (end_mtime < start_mtime){
start_mtime = CLINT_REG(CLINT_MTIME);
end_mtime = start_mtime + mtime_ticks + 1;
}
// Don't start measuring until mtime edge.
uint32_t tmp = start_mtime;
do {
start_mtime = CLINT_REG(CLINT_MTIME);
} while (start_mtime == tmp);
uint64_t start_mcycle;
rdmcycle(&start_mcycle);
while (CLINT_REG(CLINT_MTIME) < end_mtime) ;
uint64_t end_mcycle;
rdmcycle(&end_mcycle);
uint32_t difference = (uint32_t) (end_mcycle - start_mcycle);
uint64_t freq = ((uint64_t) difference * mtime_freq) / mtime_ticks;
return (uint32_t) freq & 0xFFFFFFFF;
}
static void PRCI_use_hfrosc(int div, int trim)
{
// Make sure the HFROSC is running at its default setting
// It is OK to change this even if we are running off of it.
PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0);
PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
}
static void PRCI_use_pll(int refsel, int bypass,
int r, int f, int q, int finaldiv,
int hfroscdiv, int hfrosctrim)
{
// 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
PRCI_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 {
// To overclock, use the hfrosc
if (hfrosctrim >= 0 && hfroscdiv >= 0) {
PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
}
// Set DIV Settings for PLL
// (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:
if (finaldiv == 1){
PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
} else {
PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV(finaldiv));
}
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 = CLINT_REG(CLINT_MTIME);
while (CLINT_REG(CLINT_MTIME) - 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);
}
static void PRCI_use_default_clocks()
{
// Turn off the LFROSC
AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
// Use HFROSC
PRCI_use_hfrosc(4, 16);
}
// This is a generic function, which
// doesn't span the entire range of HFROSC settings.
// It only adjusts the trim, which can span a hundred MHz or so.
// This function needs improvement to ensure that the PLL settings
// are legal every step of the way.
// It returns the actual measured CPU frequency.
uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu)
{
int hfrosctrim = 16;
PRCI_use_default_clocks();
PRCI_use_pll(0, 0, 1, 31, 1, 1, 4, 16);
// Ignore the first run (for icache reasons)
uint32_t cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
if (cpu_freq > F_CPU) {
while((cpu_freq > F_CPU) && (hfrosctrim >= 0) ){
PRCI_use_pll(0, 0, 1, 31, 1, 1, 4, hfrosctrim );
cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
hfrosctrim--;
}
return cpu_freq;
}
while(cpu_freq < F_CPU) {
if (hfrosctrim >= 0x20) {
break;
}
PRCI_use_pll(0, 0, 1, 31, 1, 1, 4, hfrosctrim );
cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
hfrosctrim++;
}
return cpu_freq;
}
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