1 /*
2  * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
3  *
4  * SPDX-License-Identifier: BSD-3-Clause
5  */
6 
7 #include "pico.h"
8 
9 // For frequency related definitions etc
10 #include "hardware/clocks.h"
11 
12 #include "hardware/platform_defs.h"
13 #include "hardware/regs/xosc.h"
14 #include "hardware/xosc.h"
15 
16 #if XOSC_KHZ < (1 * KHZ) || XOSC_KHZ > (50 * KHZ)
17 // Note: Although an external clock can be supplied up to 50 MHz, the maximum frequency the
18 // XOSC cell is specified to work with a crystal is less, please see the RP2040 Datasheet.
19 #error XOSC_KHZ must be in the range 1,000-50,000KHz i.e. 1-50MHz XOSC frequency
20 #endif
21 
22 #define STARTUP_DELAY (((XOSC_KHZ + 128) / 256) * PICO_XOSC_STARTUP_DELAY_MULTIPLIER)
23 
24 // The DELAY field in xosc_hw->startup is 14 bits wide.
25 #if STARTUP_DELAY >= (1 << 13)
26 #error PICO_XOSC_STARTUP_DELAY_MULTIPLIER is too large: XOSC STARTUP.DELAY must be < 8192
27 #endif
28 
xosc_init(void)29 void xosc_init(void) {
30     // Assumes 1-15 MHz input, checked above.
31     xosc_hw->ctrl = XOSC_CTRL_FREQ_RANGE_VALUE_1_15MHZ;
32 
33     // Set xosc startup delay
34     xosc_hw->startup = STARTUP_DELAY;
35 
36     // Set the enable bit now that we have set freq range and startup delay
37     hw_set_bits(&xosc_hw->ctrl, XOSC_CTRL_ENABLE_VALUE_ENABLE << XOSC_CTRL_ENABLE_LSB);
38 
39     // Wait for XOSC to be stable
40     while(!(xosc_hw->status & XOSC_STATUS_STABLE_BITS));
41 }
42 
xosc_disable(void)43 void xosc_disable(void) {
44     uint32_t tmp = xosc_hw->ctrl;
45     tmp &= (~XOSC_CTRL_ENABLE_BITS);
46     tmp |= (XOSC_CTRL_ENABLE_VALUE_DISABLE << XOSC_CTRL_ENABLE_LSB);
47     xosc_hw->ctrl = tmp;
48     // Wait for stable to go away
49     while(xosc_hw->status & XOSC_STATUS_STABLE_BITS);
50 }
51 
xosc_dormant(void)52 void xosc_dormant(void) {
53     // WARNING: This stops the xosc until woken up by an irq
54     xosc_hw->dormant = XOSC_DORMANT_VALUE_DORMANT;
55     // Wait for it to become stable once woken up
56     while(!(xosc_hw->status & XOSC_STATUS_STABLE_BITS));
57 }
58