add context_gcc.s

1 files changed, 238 insertions, 0 deletions

diff --git a/libcpu/risc-v/e310/init.c b/libcpu/risc-v/e310/init.c
new file mode 100644
index 0000000000..621a6e2dd6
--- /dev/null
+++ b/libcpu/risc-v/e310/init.c
@@ -0,0 +1,238 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+extern int main(int argc, char** argv);
+extern void trap_entry();
+
+static unsigned long mtime_lo(void)
+{
+  return *(volatile unsigned long *)(CLINT_CTRL_ADDR + CLINT_MTIME);
+}
+
+#ifdef __riscv32
+
+static uint32_t mtime_hi(void)
+{
+  return *(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIME + 4);
+}
+
+uint64_t get_timer_value()
+{
+  while (1) {
+    uint32_t hi = mtime_hi();
+    uint32_t lo = mtime_lo();
+    if (hi == mtime_hi())
+      return ((uint64_t)hi << 32) | lo;
+  }
+}
+
+#else /* __riscv32 */
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+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);
+}
+
+static unsigned long __attribute__((noinline)) measure_cpu_freq(size_t n)
+{
+  unsigned long start_mtime, delta_mtime;
+  unsigned long mtime_freq = get_timer_freq();
+
+  // Don't start measuruing until we see an mtime tick
+  unsigned long tmp = mtime_lo();
+  do {
+    start_mtime = mtime_lo();
+  } while (start_mtime == tmp);
+
+  unsigned long start_mcycle = read_csr(mcycle);
+
+  do {
+    delta_mtime = mtime_lo() - start_mtime;
+  } while (delta_mtime < n);
+
+  unsigned long delta_mcycle = read_csr(mcycle) - start_mcycle;
+
+  return (delta_mcycle / delta_mtime) * mtime_freq
+         + ((delta_mcycle % delta_mtime) * mtime_freq) / delta_mtime;
+}
+
+unsigned long get_cpu_freq()
+{
+  static uint32_t cpu_freq;
+
+  if (!cpu_freq) {
+    // warm up I$
+    measure_cpu_freq(1);
+    // measure for real
+    cpu_freq = measure_cpu_freq(10);
+  }
+
+  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()
+{
+  
+  #ifndef NO_INIT
+  use_default_clocks();
+  use_pll(0, 0, 1, 31, 1);
+  uart_init(115200);
+
+  printf("core freq at %d Hz\n", get_cpu_freq());
+
+  write_csr(mtvec, &trap_entry);
+  if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
+    write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
+    write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
+  }
+  #endif
+  
+}
+
+void _fini()
+{
+}