cpu/samd5: valid XOSC32 statup time avoid gclk roundtrip for CPU FDPLL

Author: kfessel

cpu/samd5x/cpu.c

@@ -107,7 +107,7 @@ static void xosc32k_init(void)
                             | OSC32KCTRL_XOSC32K_EN32K
                             | OSC32KCTRL_XOSC32K_RUNSTDBY
                             | OSC32KCTRL_XOSC32K_XTALEN
-                            | OSC32KCTRL_XOSC32K_STARTUP(7);
+                            | OSC32KCTRL_XOSC32K_STARTUP(5);
 
     while (!(OSC32KCTRL->STATUS.reg & OSC32KCTRL_STATUS_XOSC32KRDY)) {}
 }
@@ -212,10 +212,16 @@ static void fdpll_init_nolock(uint8_t idx, uint32_t f_cpu, uint8_t flags)
                                      | OSCCTRL_DPLLRATIO_LDR((LDR >> 5) - 1);
 
     /* Without LBYPASS, startup takes very long, see errata section 2.13. */
+    if(idx == 0){
+        OSCCTRL->Dpll[idx].DPLLCTRLB.reg = OSCCTRL_DPLLCTRLB_REFCLK_XOSC32;
+                                     // | OSCCTRL_DPLLCTRLB_WUF
+                                     // | OSCCTRL_DPLLCTRLB_LBYPASS;
+    }
     OSCCTRL->Dpll[idx].DPLLCTRLB.reg = OSCCTRL_DPLLCTRLB_REFCLK_GCLK
                                      | OSCCTRL_DPLLCTRLB_WUF
                                      | OSCCTRL_DPLLCTRLB_LBYPASS;
 
+
     OSCCTRL->Dpll[idx].DPLLCTRLA.reg = OSCCTRL_DPLLCTRLA_ENABLE | flags;
 
     while (OSCCTRL->Dpll[idx].DPLLSYNCBUSY.reg) {}