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samd/clock_config: Extend the range of machine.freq().

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The value given for machine.freq(f) is extend to the range of 1_000_000 to
200_000_000.  Frequencies below 48 MHz will be forced to an integer
fraction of 48 MHz.  At frequencies below 8 MHz USB is switched off.  The
power consumption e.g. of ADAFRUIT_ITSYBITSY_M4_EXPRESS drops to about
1.5 mA at 1 MHz.

Since the peripheral frequency is dropped as well, timing e.g. of PWM,
UART, I2C and SPI is affected and frequency/baud rate has to set again
after a frequency change below 48 MHz.
This commit is contained in:
robert-hh 2022-06-29 15:31:21 +02:00 committed by Damien George
parent 1ba0e8ff96
commit edc3f3d0d3
3 changed files with 52 additions and 22 deletions
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68
ports/samd/mcu/samd51/clock_config.c
View File

@ -54,35 +54,63 @@ uint32_t get_peripheral_freq(void) {
}
void set_cpu_freq(uint32_t cpu_freq_arg) {
cpu_freq = cpu_freq_arg;
// Setup GCLK0 for 48MHz as default state to keep the MCU running during config change.
GCLK->GENCTRL[0].reg = GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL0) {
}
// Setup DPLL0 for 120 MHz
// first: disable DPLL0 in case it is running
OSCCTRL->Dpll[0].DPLLCTRLA.bit.ENABLE = 0;
while (OSCCTRL->Dpll[0].DPLLSYNCBUSY.bit.ENABLE == 1) {
}
// Now configure the registers
OSCCTRL->Dpll[0].DPLLCTRLB.reg = OSCCTRL_DPLLCTRLB_DIV(1) | OSCCTRL_DPLLCTRLB_LBYPASS |
OSCCTRL_DPLLCTRLB_REFCLK(0) | OSCCTRL_DPLLCTRLB_WUF | OSCCTRL_DPLLCTRLB_FILTER(0x01);
if (cpu_freq_arg > DFLL48M_FREQ) {
uint32_t div = cpu_freq / DPLLx_REF_FREQ;
uint32_t frac = (cpu_freq - div * DPLLx_REF_FREQ) / (DPLLx_REF_FREQ / 32);
OSCCTRL->Dpll[0].DPLLRATIO.reg = (frac << 16) + div - 1;
// enable it again
OSCCTRL->Dpll[0].DPLLCTRLA.reg = OSCCTRL_DPLLCTRLA_ENABLE | OSCCTRL_DPLLCTRLA_RUNSTDBY;
cpu_freq = cpu_freq_arg;
peripheral_freq = DFLL48M_FREQ;
// Now configure the registers
OSCCTRL->Dpll[0].DPLLCTRLB.reg = OSCCTRL_DPLLCTRLB_DIV(1) | OSCCTRL_DPLLCTRLB_LBYPASS |
OSCCTRL_DPLLCTRLB_REFCLK(0) | OSCCTRL_DPLLCTRLB_WUF | OSCCTRL_DPLLCTRLB_FILTER(0x01);
// Per errata 2.13.1
while (!(OSCCTRL->Dpll[0].DPLLSTATUS.bit.CLKRDY == 1)) {
uint32_t div = cpu_freq / DPLLx_REF_FREQ;
uint32_t frac = (cpu_freq - div * DPLLx_REF_FREQ) / (DPLLx_REF_FREQ / 32);
OSCCTRL->Dpll[0].DPLLRATIO.reg = (frac << 16) + div - 1;
// enable it again
OSCCTRL->Dpll[0].DPLLCTRLA.reg = OSCCTRL_DPLLCTRLA_ENABLE | OSCCTRL_DPLLCTRLA_RUNSTDBY;
// Per errata 2.13.1
while (!(OSCCTRL->Dpll[0].DPLLSTATUS.bit.CLKRDY == 1)) {
}
// Setup GCLK0 for DPLL0 output (48 or 48-200MHz)
GCLK->GENCTRL[0].reg = GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DPLL0;
while (GCLK->SYNCBUSY.bit.GENCTRL0) {
}
// Set GCLK 2 back to 48 MHz
GCLK->GENCTRL[2].reg = GCLK_GENCTRL_DIV(1) | GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL2) {
}
} else {
int div = DFLL48M_FREQ / cpu_freq_arg;
// Setup GCLK1 for the low freq
GCLK->GENCTRL[2].reg = GCLK_GENCTRL_DIV(div) | GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL2) {
}
GCLK->GENCTRL[0].reg = GCLK_GENCTRL_DIV(div) | GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL0) {
}
peripheral_freq = DFLL48M_FREQ / div;
cpu_freq = DFLL48M_FREQ / div;
}
// Setup GCLK0 for DPLL0 output (48 or 48-200MHz)
GCLK->GENCTRL[0].reg = GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DPLL0;
while (GCLK->SYNCBUSY.bit.GENCTRL0) {
if (cpu_freq >= 8000000) {
// Setup GCLK5 for DFLL48M output (48 MHz)
GCLK->GENCTRL[5].reg = GCLK_GENCTRL_DIV(1) | GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL5) {
}
} else {
// Setup GCLK5 off if CPU Clk < 8 MHz
GCLK->GENCTRL[5].reg = 0;
while (GCLK->SYNCBUSY.bit.GENCTRL5) {
}
}
}
@ -120,9 +148,10 @@ void init_clocks(uint32_t cpu_freq) {
// SAMD51 clock settings
// GCLK0: 48MHz from DFLL48M or 48 - 200 MHz from DPLL0 (SAMD51)
// GCLK1: 32768 Hz from 32KULP or DFLL48M
// GCLK2: 48MHz from DFLL48M for Peripheral devices
// GCLK3: 16Mhz for the us-counter (TC0/TC1)
// GCLK2: 8-48MHz from DFLL48M for Peripheral devices
// GCLK3: 8Mhz for the us-counter (TC0/TC1)
// GCLK4: 32kHz from crystal, if present
// GCLK5: 48MHz from DFLL48M for USB
// DPLL0: 48 - 200 MHz
// Steps to set up clocks:
@ -136,6 +165,7 @@ void init_clocks(uint32_t cpu_freq) {
// Setup GCLK2 to 48MHz for Peripherals
// Setup GCLK3 to 8MHz for TC0/TC1
// Setup GCLK4 to 32kHz crystal, if present
// Setup GCLK5 to 48 MHz
// Setup GCLK0 for 48MHz as default state to keep the MCU running during config change.
GCLK->GENCTRL[0].reg = GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
@ -238,7 +268,7 @@ void init_clocks(uint32_t cpu_freq) {
peripheral_freq = DFLL48M_FREQ; // To be changed if CPU_FREQ < 48M
// Setup GCLK2 for DPLL1 output (48 MHz)
// Setup GCLK2 for DFLL48M output (48 MHz), may be scaled down later by calls to set_cpu_freq
GCLK->GENCTRL[2].reg = GCLK_GENCTRL_DIV(1) | GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL;
while (GCLK->SYNCBUSY.bit.GENCTRL2) {
}

4
ports/samd/modmachine.c
View File

@ -69,9 +69,9 @@ STATIC mp_obj_t machine_freq(size_t n_args, const mp_obj_t *args) {
} else {
#if defined(MCU_SAMD51)
uint32_t freq = mp_obj_get_int(args[0]);
if (freq >= 48000000 && freq <= 200000000) {
if (freq >= 1000000 && freq <= 200000000) {
set_cpu_freq(freq);
SysTick_Config(freq / 1000);
SysTick_Config(get_cpu_freq() / 1000);
}
#endif
return mp_const_none;

2
ports/samd/samd_soc.c
View File

@ -46,7 +46,7 @@ static void usb_init(void) {
PM->APBBMASK.bit.USB_ = 1;
uint8_t alt = 6; // alt G, USB
#elif defined(MCU_SAMD51)
GCLK->PCHCTRL[USB_GCLK_ID].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN_GCLK2;
GCLK->PCHCTRL[USB_GCLK_ID].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN_GCLK5;
while (GCLK->PCHCTRL[USB_GCLK_ID].bit.CHEN == 0) {
}
MCLK->AHBMASK.bit.USB_ = 1;