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#include <stdint.h>
#include <unistd.h>
#include "platform.h"
#include "encoding.h"
uint32_t cpu_freq = 0;
extern int main(int argc, char** argv);
uint32_t mtime_lo(void)
{
return *(volatile uint32_t *)(CLINT_BASE_ADDR + CLINT_MTIME);
}
uint32_t mcycle_lo(void)
{
uint32_t t;
asm volatile ("csrr %0, mcycle" : "=r" (t));
return t;
}
static void use_hfrosc(int div, int trim)
{
// Make sure the HFROSC is running at its default setting
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 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);
}
static void use_default_clocks()
{
// Turn off the LFROSC
AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
// Use HFROSC
use_hfrosc(4, 16);
}
void measure_cpu_freq(size_t n, size_t mtime_freq)
{
uint32_t start_mtime = mtime_lo();
uint32_t start_mcycle = mcycle_lo();
while (mtime_lo() - start_mtime < n) ;
uint32_t end_mtime = mtime_lo();
uint32_t end_mcycle = mcycle_lo();
cpu_freq = (end_mcycle-start_mcycle)/n*mtime_freq;
}
uint32_t get_cpu_freq()
{
return cpu_freq;
}
static void uart_init(size_t baud_rate)
{
GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
UART0_REG(UART_REG_DIV) = get_cpu_freq() / baud_rate - 1;
UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
}
#ifdef USE_PLIC
extern void handle_m_ext_interrupt();
#endif
#ifdef USE_M_TIME
extern void handle_m_time_interrupt();
#endif
uintptr_t handle_trap(uintptr_t mcause, uintptr_t epc)
{
if (0){
#ifdef USE_PLIC
// External Machine-Level interrupt from PLIC
} else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
handle_m_ext_interrupt();
#endif
#ifdef USE_M_TIME
// External Machine-Level interrupt from PLIC
} else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
handle_m_time_interrupt();
#endif
}
else {
write(1, "trap\n", 5);
_exit(1 + mcause);
}
return epc;
}
void _init()
{
use_default_clocks();
use_pll(0, 0, 1, 31, 1);
measure_cpu_freq(1000, 32768);
uart_init(115200);
printf("core freq at %d Hz\n", get_cpu_freq());
write_csr(mtvec, &handle_trap);
_exit(main(0, NULL));
}
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