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-rw-r--r--bsp/drivers/fe300prci/fe300prci_driver.c187
-rw-r--r--bsp/drivers/fe300prci/fe300prci_driver.h54
-rw-r--r--bsp/env/hifive1.h2
3 files changed, 243 insertions, 0 deletions
diff --git a/bsp/drivers/fe300prci/fe300prci_driver.c b/bsp/drivers/fe300prci/fe300prci_driver.c
new file mode 100644
index 0000000..3338b81
--- /dev/null
+++ b/bsp/drivers/fe300prci/fe300prci_driver.c
@@ -0,0 +1,187 @@
+// 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;
+}
diff --git a/bsp/drivers/fe300prci/fe300prci_driver.h b/bsp/drivers/fe300prci/fe300prci_driver.h
new file mode 100644
index 0000000..052edcb
--- /dev/null
+++ b/bsp/drivers/fe300prci/fe300prci_driver.h
@@ -0,0 +1,54 @@
+// See LICENSE file for license details
+
+#ifndef _FE300PRCI_DRIVER_H_
+#define _FE300PRCI_DRIVER_H_
+
+#include <unistd.h>
+
+
+/* Measure and return the approximate frequency of the
+ * CPU, as given by measuring the mcycle counter against
+ * the mtime ticks.
+ */
+static uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq);
+
+/* Safely switch over to the HFROSC using the given div
+ * and trim settings.
+ */
+static void PRCI_use_hfrosc(int div, int trim);
+
+/* Safely switch over to the PLL using the given
+ * settings.
+ *
+ * Note that not all combinations of the inputs are actually
+ * legal, and this function does not check for their
+ * legality ("safely" means that this function won't turn off
+ * or glitch the clock the CPU is actually running off, but
+ * doesn't protect against you making it too fast or slow.)
+ */
+
+static void PRCI_use_pll(int refsel, int bypass,
+ int r, int f, int q, int finaldiv,
+ int hfroscdiv, int hfrosctrim);
+
+/* Use the default clocks configured at reset.
+ * This is ~16Mhz HFROSC and turns off the LFROSC
+ * (on the current FE310 Dev Platforms, an external LFROSC is
+ * used as it is more power efficient).
+ */
+static void PRCI_use_default_clocks();
+
+/* This routine will adjust the HFROSC trim
+ * as the PLL clock source, measure the resulting
+ * frequency, and attempt to get close to the requested
+ * frequency. It returns the actual measured frequency.
+ *
+ * Note that the requested frequency must be within the
+ * range supported by the PLL so not all values are
+ * achievable with this function, and not all
+ * are guaranteed to actually work.
+ */
+uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu);
+
+#endif
+
diff --git a/bsp/env/hifive1.h b/bsp/env/hifive1.h
index 11b98f8..4c65f18 100644
--- a/bsp/env/hifive1.h
+++ b/bsp/env/hifive1.h
@@ -74,6 +74,8 @@
#define HAS_HFXOSC 1
#define HAS_LFROSC_BYPASS 1
+#define RTC_FREQ 32768
+
void write_hex(int fd, uint32_t hex);
#endif /* _SIFIVE_HIFIVE1_H */
generated by cgit v1.2.3 (git 2.25.1) at 2025-11-04 07:23:05 +0000