src/rp2_common/pico_multicore/include/pico/multicore.h

/*
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#ifndef _PICO_MULTICORE_H
#define _PICO_MULTICORE_H

#include "pico/types.h"
#include "pico/sync.h"
#include "hardware/structs/sio.h"

#ifdef __cplusplus
extern "C" {
#endif

/** \file multicore.h
 *  \defgroup pico_multicore pico_multicore
 * Adds support for running code on the second processor core (core 1)
 *
 * \subsection multicore_example Example
 * \addtogroup pico_multicore
 * \include multicore.c
*/

// PICO_CONFIG: PICO_CORE1_STACK_SIZE, Stack size for core 1, min=0x100, max=0x10000, default=PICO_STACK_SIZE (0x800), group=pico_multicore
#ifndef PICO_CORE1_STACK_SIZE
#ifdef PICO_STACK_SIZE
#define PICO_CORE1_STACK_SIZE PICO_STACK_SIZE
#else
#define PICO_CORE1_STACK_SIZE 0x800
#endif
#endif

/*! \brief  Reset core 1
 *  \ingroup pico_multicore
 *
 * This function can be used to reset core 1 into its initial state (ready for launching code against via \ref multicore_launch_core1 and similar methods)
 *
 * \note this function should only be called from core 0
 */
void multicore_reset_core1(void);

/*! \brief  Run code on core 1
 *  \ingroup pico_multicore
 *
 * Wake up (a previously reset) core 1 and enter the given function on core 1 using the default core 1 stack (below core 0 stack).
 *
 * core 1 must previously have been reset either as a result of a system reset or by calling \ref multicore_reset_core1
 *
 * core 1 will use the same vector table as core 0
 *
 * \param entry Function entry point
 * \see multicore_reset_core1
 */
void multicore_launch_core1(void (*entry)(void));

/*! \brief  Launch code on core 1 with stack
 *  \ingroup pico_multicore
 *
 * Wake up (a previously reset) core 1 and enter the given function on core 1 using the passed stack for core 1
 *
 * core 1 must previously have been reset either as a result of a system reset or by calling \ref multicore_reset_core1
 *
 * core 1 will use the same vector table as core 0
 *
 * \param entry Function entry point
 * \param stack_bottom The bottom (lowest address) of the stack
 * \param stack_size_bytes The size of the stack in bytes (must be a multiple of 4)
 * \see multicore_reset_core1
 */
void multicore_launch_core1_with_stack(void (*entry)(void), uint32_t *stack_bottom, size_t stack_size_bytes);

/*! \brief  Launch code on core 1 with no stack protection
 *  \ingroup pico_multicore
 *
 * Wake up (a previously reset) core 1 and start it executing with a specific entry point, stack pointer
 * and vector table.
 *
 * This is a low level function that does not provide a stack guard even if USE_STACK_GUARDS is defined
 *
 * core 1 must previously have been reset either as a result of a system reset or by calling \ref multicore_reset_core1
 *
 * \param entry Function entry point
 * \param sp Pointer to the top of the core 1 stack
 * \param vector_table address of the vector table to use for core 1
 * \see multicore_reset_core1
 */
void multicore_launch_core1_raw(void (*entry)(void), uint32_t *sp, uint32_t vector_table);

/*!
 * \defgroup multicore_fifo fifo
 * \ingroup pico_multicore
 * \brief Functions for the inter-core FIFOs
 *
 * The RP2040 contains two FIFOs for passing data, messages or ordered events between the two cores. Each FIFO is 32 bits
 * wide, and 8 entries deep. One of the FIFOs can only be written by core 0, and read by core 1. The other can only be written
 * by core 1, and read by core 0.
 *
 * \note The inter-core FIFOs are a very precious resource and are frequently used for SDK functionality (e.g. during
 * core 1 launch or by the \ref multicore_lockout functions). Additionally they are often required for the exclusive use
 * of an RTOS (e.g. FreeRTOS SMP). For these reasons it is suggested that you do not use the FIFO for your own purposes
 * unless none of the above concerns apply; the majority of cases for transferring data between cores can be eqaully
 * well handled  by using a \ref queue
 */

/*! \brief Check the read FIFO to see if there is data available (sent by the other core)
 *  \ingroup multicore_fifo
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 * \return true if the FIFO has data in it, false otherwise
 */
static inline bool multicore_fifo_rvalid(void) {
    return !!(sio_hw->fifo_st & SIO_FIFO_ST_VLD_BITS);
}

/*! \brief Check the write FIFO to see if it has space for more data
 *  \ingroup multicore_fifo
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 *  @return true if the FIFO has room for more data, false otherwise
 */
static inline bool multicore_fifo_wready(void) {
    return !!(sio_hw->fifo_st & SIO_FIFO_ST_RDY_BITS);
}

/*! \brief Push data on to the write FIFO (data to the other core).
 *  \ingroup multicore_fifo
 *
 * This function will block until there is space for the data to be sent.
 * Use multicore_fifo_wready() to check if it is possible to write to the
 * FIFO if you don't want to block.
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 * \param data A 32 bit value to push on to the FIFO
 */
void multicore_fifo_push_blocking(uint32_t data);

/*! \brief Push data on to the write FIFO (data to the other core) with timeout.
 *  \ingroup multicore_fifo
 *
 * This function will block until there is space for the data to be sent
 * or the timeout is reached
 *
 * \param data A 32 bit value to push on to the FIFO
 * \param timeout_us the timeout in microseconds
 * \return true if the data was pushed, false if the timeout occurred before data could be pushed
 */
bool multicore_fifo_push_timeout_us(uint32_t data, uint64_t timeout_us);

/*! \brief Pop data from the read FIFO (data from the other core).
 *  \ingroup multicore_fifo
 *
 * This function will block until there is data ready to be read
 * Use multicore_fifo_rvalid() to check if data is ready to be read if you don't
 * want to block.
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 * \return 32 bit data from the read FIFO.
 */
uint32_t multicore_fifo_pop_blocking(void);

/*! \brief Pop data from the read FIFO (data from the other core) with timeout.
 *  \ingroup multicore_fifo
 *
 * This function will block until there is data ready to be read or the timeout is reached
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 * \param timeout_us the timeout in microseconds
 * \param out the location to store the popped data if available
 * \return true if the data was popped and a value copied into `out`, false if the timeout occurred before data could be popped
 */
bool multicore_fifo_pop_timeout_us(uint64_t timeout_us, uint32_t *out);

/*! \brief Discard any data in the read FIFO
 *  \ingroup multicore_fifo
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 */
static inline void multicore_fifo_drain(void) {
    while (multicore_fifo_rvalid())
        (void) sio_hw->fifo_rd;
}

/*! \brief Clear FIFO interrupt
 *  \ingroup multicore_fifo
 *
 * Note that this only clears an interrupt that was caused by the ROE or WOF flags.
 * To clear the VLD flag you need to use one of the 'pop' or 'drain' functions.
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
 * \see multicore_fifo_get_status
*/
static inline void multicore_fifo_clear_irq(void) {
    // Write any value to clear the error flags
    sio_hw->fifo_st = 0xff;
}

/*! \brief Get FIFO statuses
 *  \ingroup multicore_fifo
 *
 * \return The statuses as a bitfield
 *
 * Bit | Description
 * ----|------------
 * 3 | Sticky flag indicating the RX FIFO was read when empty (ROE). This read was ignored by the FIFO.
 * 2 | Sticky flag indicating the TX FIFO was written when full (WOF). This write was ignored by the FIFO.
 * 1 | Value is 1 if this core’s TX FIFO is not full (i.e. if FIFO_WR is ready for more data)
 * 0 | Value is 1 if this core’s RX FIFO is not empty (i.e. if FIFO_RD is valid)
 *
 * See the note in the \ref multicore_fifo section for considerations regarding use of the inter-core FIFOs
 *
*/
static inline uint32_t multicore_fifo_get_status(void) {
    return sio_hw->fifo_st;
}

/*!
 * \defgroup multicore_lockout lockout
 * \ingroup pico_multicore
 * \brief Functions to enable one core to force the other core to pause execution in a known state.
 *
 * Sometimes it is useful to enter a critical section on both cores at once. On a single
 * core system a critical section can trivially be entered by disabling interrupts, however on a multi-core
 * system that is not sufficient, and unless the other core is polling in some way, then it will need to be interrupted
 * in order to cooperatively enter a blocked state.
 *
 * These "lockout" functions use the inter core FIFOs to cause an interrupt on one core from the other, and manage
 * waiting for the other core to enter the "locked out" state.
 *
 * The usage is that the "victim" core ... i.e the core that can be "locked out" by the other core calls
 * \ref multicore_lockout_victim_init to hook the FIFO interrupt. Note that either or both cores may do this.
 *
 * \note When "locked out" the victim core is paused (it is actually executing a tight loop with code in RAM) and has interrupts disabled.
 * This makes the lockout functions suitable for use by code that wants to write to flash (at which point no code may be executing
 * from flash)
 *
 * The core which wishes to lockout the other core calls \ref multicore_lockout_start_blocking or
 * \ref multicore_lockout_start_timeout_us to interrupt the other "victim" core and wait for it to be in a
 * "locked out" state. Once the lockout is no longer needed it calls \ref multicore_lockout_end_blocking or
 * \ref multicore_lockout_end_timeout_us to release the lockout and wait for confirmation.
 *
 * \note Because multicore lockout uses the intercore FIFOs, the FIFOs <b>cannot</b> be used for any other purpose
 */

/*! \brief Initialize the current core such that it can be a "victim" of lockout (i.e. forced to pause in a known state by the other core)
 *  \ingroup multicore_lockout
 *
 * This code hooks the intercore FIFO IRQ, and the FIFO may not be used for any other purpose after this.
 */
void multicore_lockout_victim_init(void);

/*! \brief Request the other core to pause in a known state and wait for it to do so
 *  \ingroup multicore_lockout
 *
 * The other (victim) core must have previously executed \ref multicore_lockout_victim_init()
 *
 * \note multicore_lockout_start_ functions are not nestable, and must be paired with a call to a corresponding
 * \ref multicore_lockout_end_blocking
 */
void multicore_lockout_start_blocking(void);

/*! \brief Request the other core to pause in a known state and wait up to a time limit for it to do so
 *  \ingroup multicore_lockout
 *
 * The other core must have previously executed \ref multicore_lockout_victim_init()
 *
 * \note multicore_lockout_start_ functions are not nestable, and must be paired with a call to a corresponding
 * \ref multicore_lockout_end_blocking
 *
 * \param timeout_us the timeout in microseconds
 * \return true if the other core entered the locked out state within the timeout, false otherwise
 */
bool multicore_lockout_start_timeout_us(uint64_t timeout_us);

/*! \brief Release the other core from a locked out state amd wait for it to acknowledge
 *  \ingroup multicore_lockout
 *
 * \note The other core must previously have been "locked out" by calling a `multicore_lockout_start_` function
 * from this core
 */
void multicore_lockout_end_blocking(void);

/*! \brief Release the other core from a locked out state amd wait up to a time limit for it to acknowledge
 *  \ingroup multicore_lockout
 *
 * The other core must previously have been "locked out" by calling a `multicore_lockout_start_` function
 * from this core
 *
 * \note be very careful using small timeout values, as a timeout here will leave the "lockout" functionality
 * in a bad state. It is probably preferable to use \ref multicore_lockout_end_blocking anyway as if you have
 * already waited for the victim core to enter the lockout state, then the victim core will be ready to exit
 * the lockout state very quickly.
 *
 * \param timeout_us the timeout in microseconds
 * \return true if the other core successfully exited locked out state within the timeout, false otherwise
 */
bool multicore_lockout_end_timeout_us(uint64_t timeout_us);

#ifdef __cplusplus
}
#endif
#endif