esp-idf/components/driver/include/esp_private/spi_common_internal.h

/*
 * SPDX-FileCopyrightText: 2010-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

// Internal header, don't use it in the user code

#pragma once

#include <esp_intr_alloc.h>
#include "driver/spi_common.h"
#include "freertos/FreeRTOS.h"
#include "hal/spi_types.h"
#include "esp_pm.h"

#ifdef __cplusplus
extern "C"
{
#endif


#ifdef CONFIG_SPI_MASTER_ISR_IN_IRAM
#define SPI_MASTER_ISR_ATTR IRAM_ATTR
#else
#define SPI_MASTER_ISR_ATTR
#endif

#ifdef CONFIG_SPI_MASTER_IN_IRAM
#define SPI_MASTER_ATTR IRAM_ATTR
#else
#define SPI_MASTER_ATTR
#endif


#define BUS_LOCK_DEBUG  0

#if BUS_LOCK_DEBUG
#define BUS_LOCK_DEBUG_EXECUTE_CHECK(x)  assert(x)
#else
#define BUS_LOCK_DEBUG_EXECUTE_CHECK(x)
#endif


struct spi_bus_lock_t;
struct spi_bus_lock_dev_t;
/// Handle to the lock of an SPI bus
typedef struct spi_bus_lock_t* spi_bus_lock_handle_t;
/// Handle to lock of one of the device on an SPI bus
typedef struct spi_bus_lock_dev_t* spi_bus_lock_dev_handle_t;

/// Background operation control function
typedef void (*bg_ctrl_func_t)(void*);

typedef struct lldesc_s lldesc_t;

/// Attributes of an SPI bus
typedef struct {
    spi_bus_config_t bus_cfg;   ///< Config used to initialize the bus
    uint32_t flags;             ///< Flags (attributes) of the bus
    int max_transfer_sz;        ///< Maximum length of bytes available to send
    bool dma_enabled;           ///< To enable DMA or not
    int tx_dma_chan;            ///< TX DMA channel, on ESP32 and ESP32S2, tx_dma_chan and rx_dma_chan are same
    int rx_dma_chan;            ///< RX DMA channel, on ESP32 and ESP32S2, tx_dma_chan and rx_dma_chan are same
    int dma_desc_num;           ///< DMA descriptor number of dmadesc_tx or dmadesc_rx.
    lldesc_t *dmadesc_tx;       ///< DMA descriptor array for TX
    lldesc_t *dmadesc_rx;       ///< DMA descriptor array for RX
    spi_bus_lock_handle_t lock;
#ifdef CONFIG_PM_ENABLE
    esp_pm_lock_handle_t pm_lock;   ///< Power management lock
#endif
} spi_bus_attr_t;

/// Destructor called when a bus is deinitialized.
typedef esp_err_t (*spi_destroy_func_t)(void*);


/**
 * @brief Try to claim a SPI peripheral
 *
 * Call this if your driver wants to manage a SPI peripheral.
 *
 * @param host Peripheral to claim
 * @param source The caller indentification string.
 *
 * @return True if peripheral is claimed successfully; false if peripheral already is claimed.
 */
bool spicommon_periph_claim(spi_host_device_t host, const char* source);

/**
 * @brief Check whether the spi periph is in use.
 *
 * @param host Peripheral to check.
 *
 * @return True if in use, otherwise false.
 */
bool spicommon_periph_in_use(spi_host_device_t host);

/**
 * @brief Return the SPI peripheral so another driver can claim it.
 *
 * @param host Peripheral to return
 *
 * @return True if peripheral is returned successfully; false if peripheral was free to claim already.
 */
bool spicommon_periph_free(spi_host_device_t host);

/**
 * @brief Alloc DMA for SPI
 *
 * @param host_id                      SPI host ID
 * @param dma_chan                     DMA channel to be used
 * @param[out] out_actual_tx_dma_chan  Actual TX DMA channel (if you choose to assign a specific DMA channel, this will be the channel you assigned before)
 * @param[out] out_actual_rx_dma_chan  Actual RX DMA channel (if you choose to assign a specific DMA channel, this will be the channel you assigned before)
 *
 * @return
 *        - ESP_OK:                On success
 *        - ESP_ERR_NO_MEM:        No enough memory
 *        - ESP_ERR_NOT_FOUND:     There is no available DMA channel
 */
esp_err_t spicommon_dma_chan_alloc(spi_host_device_t host_id, spi_dma_chan_t dma_chan, uint32_t *out_actual_tx_dma_chan, uint32_t *out_actual_rx_dma_chan);

/**
 * @brief Free DMA for SPI
 *
 * @param host_id  SPI host ID
 *
 * @return
 *        - ESP_OK: On success
 */
esp_err_t spicommon_dma_chan_free(spi_host_device_t host_id);

/**
 * @brief Connect a SPI peripheral to GPIO pins
 *
 * This routine is used to connect a SPI peripheral to the IO-pads and DMA channel given in
 * the arguments. Depending on the IO-pads requested, the routing is done either using the
 * IO_mux or using the GPIO matrix.
 *
 * @param host SPI peripheral to be routed
 * @param bus_config Pointer to a spi_bus_config struct detailing the GPIO pins
 * @param flags Combination of SPICOMMON_BUSFLAG_* flags, set to ensure the pins set are capable with some functions:
 *              - ``SPICOMMON_BUSFLAG_MASTER``: Initialize I/O in master mode
 *              - ``SPICOMMON_BUSFLAG_SLAVE``: Initialize I/O in slave mode
 *              - ``SPICOMMON_BUSFLAG_IOMUX_PINS``: Pins set should match the iomux pins of the controller.
 *              - ``SPICOMMON_BUSFLAG_SCLK``, ``SPICOMMON_BUSFLAG_MISO``, ``SPICOMMON_BUSFLAG_MOSI``:
 *                  Make sure SCLK/MISO/MOSI is/are set to a valid GPIO. Also check output capability according to the mode.
 *              - ``SPICOMMON_BUSFLAG_DUAL``: Make sure both MISO and MOSI are output capable so that DIO mode is capable.
 *              - ``SPICOMMON_BUSFLAG_WPHD`` Make sure WP and HD are set to valid output GPIOs.
 *              - ``SPICOMMON_BUSFLAG_QUAD``: Combination of ``SPICOMMON_BUSFLAG_DUAL`` and ``SPICOMMON_BUSFLAG_WPHD``.
 *              - ``SPICOMMON_BUSFLAG_IO4_IO7``: Make sure spi data4 ~ spi data7 are set to valid output GPIOs.
 *              - ``SPICOMMON_BUSFLAG_OCTAL``: Combination of ``SPICOMMON_BUSFLAG_QUAL`` and ``SPICOMMON_BUSFLAG_IO4_IO7``.
 * @param[out] flags_o A SPICOMMON_BUSFLAG_* flag combination of bus abilities will be written to this address.
 *              Leave to NULL if not needed.
 *              - ``SPICOMMON_BUSFLAG_IOMUX_PINS``: The bus is connected to iomux pins.
 *              - ``SPICOMMON_BUSFLAG_SCLK``, ``SPICOMMON_BUSFLAG_MISO``, ``SPICOMMON_BUSFLAG_MOSI``: The bus has
 *                  CLK/MISO/MOSI connected.
 *              - ``SPICOMMON_BUSFLAG_DUAL``: The bus is capable with DIO mode.
 *              - ``SPICOMMON_BUSFLAG_WPHD`` The bus has WP and HD connected.
 *              - ``SPICOMMON_BUSFLAG_QUAD``: Combination of ``SPICOMMON_BUSFLAG_DUAL`` and ``SPICOMMON_BUSFLAG_WPHD``.
 *              - ``SPICOMMON_BUSFLAG_IO4_IO7``: The bus has spi data4 ~ spi data7 connected.
 *              - ``SPICOMMON_BUSFLAG_OCTAL``: Combination of ``SPICOMMON_BUSFLAG_QUAL`` and ``SPICOMMON_BUSFLAG_IO4_IO7``.
 * @return
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_OK                on success
 */
esp_err_t spicommon_bus_initialize_io(spi_host_device_t host, const spi_bus_config_t *bus_config, uint32_t flags, uint32_t *flags_o);

/**
 * @brief Free the IO used by a SPI peripheral
 *
 * @param bus_cfg Bus config struct which defines which pins to be used.
 *
 * @return
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_OK                on success
 */
esp_err_t spicommon_bus_free_io_cfg(const spi_bus_config_t *bus_cfg);

/**
 * @brief Initialize a Chip Select pin for a specific SPI peripheral
 *
 * @param host SPI peripheral
 * @param cs_io_num GPIO pin to route
 * @param cs_num CS id to route
 * @param force_gpio_matrix If true, CS will always be routed through the GPIO matrix. If false,
 *                          if the GPIO number allows it, the routing will happen through the IO_mux.
 */
void spicommon_cs_initialize(spi_host_device_t host, int cs_io_num, int cs_num, int force_gpio_matrix);

/**
 * @brief Free a chip select line
 *
 * @param cs_gpio_num CS gpio num to free
 */
void spicommon_cs_free_io(int cs_gpio_num);

/**
 * @brief Check whether all pins used by a host are through IOMUX.
 *
 * @param host SPI peripheral
 *
 * @return false if any pins are through the GPIO matrix, otherwise true.
 */
bool spicommon_bus_using_iomux(spi_host_device_t host);

/**
 * @brief Get the IRQ source for a specific SPI host
 *
 * @param host The SPI host
 *
 * @return The hosts IRQ source
 */
int spicommon_irqsource_for_host(spi_host_device_t host);

/**
 * @brief Get the IRQ source for a specific SPI DMA
 *
 * @param host The SPI host
 *
 * @return The hosts IRQ source
 */
int spicommon_irqdma_source_for_host(spi_host_device_t host);

/**
 * Callback, to be called when a DMA engine reset is completed
*/
typedef void(*dmaworkaround_cb_t)(void *arg);


/**
 * @brief Request a reset for a certain DMA channel
 *
 * @note In some (well-defined) cases in the ESP32 (at least rev v.0 and v.1), a SPI DMA channel will get confused. This can be remedied
 * by resetting the SPI DMA hardware in case this happens. Unfortunately, the reset knob used for thsi will reset _both_ DMA channels, and
 * as such can only done safely when both DMA channels are idle. These functions coordinate this.
 *
 * Essentially, when a reset is needed, a driver can request this using spicommon_dmaworkaround_req_reset. This is supposed to be called
 * with an user-supplied function as an argument. If both DMA channels are idle, this call will reset the DMA subsystem and return true.
 * If the other DMA channel is still busy, it will return false; as soon as the other DMA channel is done, however, it will reset the
 * DMA subsystem and call the callback. The callback is then supposed to be used to continue the SPI drivers activity.
 *
 * @param dmachan DMA channel associated with the SPI host that needs a reset
 * @param cb Callback to call in case DMA channel cannot be reset immediately
 * @param arg Argument to the callback
 *
 * @return True when a DMA reset could be executed immediately. False when it could not; in this
 *         case the callback will be called with the specified argument when the logic can execute
 *         a reset, after that reset.
 */
bool spicommon_dmaworkaround_req_reset(int dmachan, dmaworkaround_cb_t cb, void *arg);


/**
 * @brief Check if a DMA reset is requested but has not completed yet
 *
 * @return True when a DMA reset is requested but hasn't completed yet. False otherwise.
 */
bool spicommon_dmaworkaround_reset_in_progress(void);


/**
 * @brief Mark a DMA channel as idle.
 *
 * A call to this function tells the workaround logic that this channel will
 * not be affected by a global SPI DMA reset.
 */
void spicommon_dmaworkaround_idle(int dmachan);

/**
 * @brief Mark a DMA channel as active.
 *
 * A call to this function tells the workaround logic that this channel will
 * be affected by a global SPI DMA reset, and a reset like that should not be attempted.
 */
void spicommon_dmaworkaround_transfer_active(int dmachan);

/*******************************************************************************
 * Bus attributes
 ******************************************************************************/
/**
 * @brief Set bus lock for the main bus, called by startup code.
 *
 * @param lock The lock to be used by the main SPI bus.
 */
void spi_bus_main_set_lock(spi_bus_lock_handle_t lock);

/**
 * @brief Get the attributes of a specified SPI bus.
 *
 * @param host_id The specified host to get attribute
 * @return (Const) Pointer to the attributes
 */
const spi_bus_attr_t* spi_bus_get_attr(spi_host_device_t host_id);

/**
 * @brief Register a function to a initialized bus to make it called when deinitializing the bus.
 *
 * @param host_id   The SPI bus to register the destructor.
 * @param f         Destructor to register
 * @param arg       The argument to call the destructor
 * @return Always ESP_OK.
 */
esp_err_t spi_bus_register_destroy_func(spi_host_device_t host_id,
                                        spi_destroy_func_t f, void *arg);

/*******************************************************************************
 * SPI Bus Lock for arbitration among SPI master (intr, polling) trans, SPI flash operations and
 * flash/psram cache access.
 *
 * NON-PUBLIC API. Don't use it directly in applications.
 *
 * There is the main lock corresponding to an SPI bus, of which several devices (holding child
 * locks) attaching to it. Each of the device is STRONGLY RECOMMENDED to be used in only one task
 * to avoid concurrency issues.
 *
 * Terms:
 * - BG operations (BackGround operations) means some transaction that will not immediately /
 *   explicitly be sent in the task. It can be some cache access, or interrupt transactions.
 *
 * - Operation: usage of the bus, for example, do SPI transactions.
 *
 * - Acquiring processor: the task or the ISR that is allowed to use the bus. No operations will be
 *   performed if there is no acquiring processor. A processor becomes the acquiring processor if
 *   it ask for that when no acquiring processor exist, otherwise it has to wait for the acquiring
 *   processor to handle over the role to it. The acquiring processor will and will only assign one
 *   acquiring processor in the waiting list (if not empty) when it finishes its operation.
 *
 * - Acquiring device: the only device allowed to use the bus. Operations can be performed in
 *   either the BG or the task. When there's no acquiring device, only the ISR is allowed to be the
 *   acquiring processor and perform operations on the bus.
 *
 * When a device wants to perform operations, it either:
 * 1. Acquire the bus, and operate in the task (e.g. polling transactions of SPI master, and SPI flash
 *    operations)
 *
 * 2. Request a BG operation. And the ISR will be enabled at proper time.
 *
 *    For example if a task wants to send an interrupt transaction, it prepares the data in the task,
 *    call `spi_bus_lock_bg_request`, and handle sending in the ISR.
 *
 * 3. When a device has already acquired the bus, BG operations are also allowed. After the
 *    `spi_bus_lock_bg_request` is called, call `spi_bus_lock_wait_bg_done` before operations in task
 *    again to wait until BG operations are done.
 *
 * Any device may try to invoke the ISR (by `spi_bus_lock_bg_request`). The ISR will be invoked and
 * become the acquiring processor immediately when the bus is not acquired by other processors. Any
 * device may also try to acquire the bus (by `spi_bus_lock_acquire_start`). The device will become
 * the acquiring processor immediately when the bus is not acquired and there is no request active.
 *
 * The acquiring processor must be aware of its acquiring role, and properly transfer the acquiring
 * processor to other tasks or ISR when they have nothing else to do. Before picking a new
 * acquiring processor, a new acquiring device must be picked first, if there are other devices,
 * asking to be acquiring device. After that, the new acquiring processor is picked by the sequence
 * below:
 *
 * 1. If there is an acquiring device:
 *      1.1 The ISR, if acquiring device has active BG requests
 *      1.2 The task of the device, if no active BG request for the device
 * 2. The ISR, if there's no acquiring device, but any BG request is active
 * 3. No one becomes the acquiring processor
 *
 * The API also helps on the arbitration of SPI cs lines. The bus is initialized with a cs_num
 * argument. When attaching devices onto the bus with `spi_bus_lock_register_dev`, it will allocate
 * devices with different device ID according to the flags given. If the ID is smaller than the
 * cs_num given when bus is initialized, error will be returned.
 *
 * Usage:
 * * Initialization:
 * 1. Call `spi_bus_init_lock` to register a lock for a bus.
 * 2. Call `spi_bus_lock_set_bg_control` to prepare BG enable/disable functions for
 *    the lock.
 * 3. Call `spi_bus_lock_register_dev` for each devices that may make use of the
 *    bus, properly store the returned handle, representing those devices.
 *
 * * Acquiring:
 * 1. Call `spi_bus_lock_acquire_start` when a device wants to use the bus
 * 2. Call `spi_bus_lock_touch` to mark the bus as touched by this device. Also check if the bus
 *    has been touched by other devices.
 * 3. (optional) Do something on the bus...
 * 4. (optional) Call `spi_bus_lock_bg_request` to inform and invoke the BG. See ISR below about
 *    ISR operations.
 * 5. (optional) If `spi_bus_lock_bg_request` is done, you have to call `spi_bus_lock_wait_bg_done`
 *    before touching the bus again, or do the following steps.
 * 6. Call `spi_bus_lock_acquire_end` to release the bus to other devices.
 *
 * * ISR:
 * 1. Call `spi_bus_lock_bg_entry` when entering the ISR, run or skip the closure for the previous
 *    operation according to the return value.
 * 2. Call `spi_bus_lock_get_acquiring_dev` to get the acquiring device. If there is no acquiring
 *    device, call `spi_bus_lock_bg_check_dev_acq` to check and update a new acquiring device.
 * 3. Call `spi_bus_lock_bg_check_dev_req` to check for request of the desired device. If the
 *    desired device is not requested, go to step 5.
 * 4. Check, start operation for the desired device and go to step 6; otherwise if no operations
 *    can be performed, call `spi_bus_lock_bg_clear_req` to clear the request for this device. If
 *    `spi_bus_lock_bg_clear_req` is called and there is no BG requests active, goto step 6.
 * 5. (optional) If the device is the acquiring device, go to step 6, otherwise
 *    find another desired device, and go back to step 3.
 * 6. Call `spi_bus_lock_bg_exit` to try quitting the ISR. If failed, go back to step 2 to look for
 *    a new request again. Otherwise, quit the ISR.
 *
 * * Deinitialization (optional):
 * 1. Call `spi_bus_lock_unregister_dev` for each device when they are no longer needed.
 * 2. Call `spi_bus_deinit_lock` to release the resources occupied by the lock.
 *
 * Some technical details:
 *
 * The child-lock of each device will have its own Binary Semaphore, which allows the task serving
 * this device (task A) being blocked when it fail to become the acquiring processor while it's
 * calling `spi_bus_lock_acquire_start` or `spi_bus_lock_wait_bg_done`. If it is blocked, there
 * must be an acquiring processor (either the ISR or another task (task B)), is doing transaction
 * on the bus. After that, task A will get unblocked and become the acquiring processor when the
 * ISR call `spi_bus_lock_bg_resume_acquired_dev`, or task B call `spi_bus_lock_acquire_end`.
 *
 * When the device wants to send ISR transaction, it should call `spi_bus_lock_bg_request` after
 * the data is prepared. This function sets a request bit in the critical resource. The ISR will be
 * invoked and become the new acquiring processor, when:
 *
 * 1. A task calls `spi_bus_lock_bg_request` while there is no acquiring processor;
 * 2. A tasks calls `spi_bus_lock_bg_request` while the task is the acquiring processor. Then the
 *    acquiring processor is handled over to the ISR;
 * 3. A tasks who is the acquiring processor release the bus by calling `spi_bus_lock_acquire_end`,
 *    and the ISR happens to be the next acquiring processor.
 *
 * The ISR will check (by `spi_bus_lock_bg_check_dev_req`) and clear a request bit (by
 * `spi_bus_lock_bg_clear_req`) after it confirm that all the requests of the corresponding device
 * are served. The request bit supports being written to recursively, which means, the task don't
 * need to wait for `spi_bus_lock_bg_clear_req` before call another `spi_bus_lock_bg_request`. The
 * API will handle the concurrency conflicts properly.
 *
 * The `spi_bus_lock_bg_exit` (together with `spi_bus_lock_bg_entry` called before)` is responsible
 * to ensure ONE and ONLY ONE of the following will happen when the ISR try to give up its
 * acquiring processor rule:
 *
 * 1. ISR quit, no any task unblocked while the interrupt disabled, and none of the BG bits is
 *    active.
 * 2. ISR quit, there is an acquiring device, and the acquiring processor is passed to the task
 *    serving the acquiring device by unblocking the task.
 * 3. The ISR failed to quit and have to try again.
 ******************************************************************************/

#define DEV_NUM_MAX 6     ///< Number of devices supported by this lock

/// Lock configuration struct
typedef struct {
    int host_id;    ///< SPI host id
    int cs_num;     ///< Physical cs numbers of the host
} spi_bus_lock_config_t;

/// Child-lock configuration struct
typedef struct {
    uint32_t flags; ///< flags for the lock, OR-ed of `SPI_BUS_LOCK_DEV_*` flags.
#define SPI_BUS_LOCK_DEV_FLAG_CS_REQUIRED   BIT(0)  ///< The device needs a physical CS pin.
} spi_bus_lock_dev_config_t;

/************* Common *********************/
/**
 * Initialize a lock for an SPI bus.
 *
 * @param out_lock Output of the handle to the lock
 * @return
 *  - ESP_ERR_NO_MEM: if memory exhausted
 *  - ESP_OK: if success
 */
esp_err_t spi_bus_init_lock(spi_bus_lock_handle_t *out_lock, const spi_bus_lock_config_t *config);

/**
 * Free the resources used by an SPI bus lock.
 *
 * @note All attached devices should have been unregistered before calling this
 *       funciton.
 *
 * @param lock Handle to the lock to free.
 */
void spi_bus_deinit_lock(spi_bus_lock_handle_t lock);

/**
 * @brief Get the corresponding lock according to bus id.
 *
 * @param host_id The bus id to get the lock
 * @return The lock handle
 */
spi_bus_lock_handle_t spi_bus_lock_get_by_id(spi_host_device_t host_id);

/**
 * @brief Configure how the SPI bus lock enable the background operation.
 *
 * @note The lock will not try to stop the background operations, but wait for
 *       The background operations finished indicated by `spi_bus_lock_bg_resume_acquired_dev`.
 *
 * @param lock Handle to the lock to set
 * @param bg_enable The enabling function
 * @param bg_disable The disabling function, set to NULL if not required
 * @param arg Argument to pass to the enabling/disabling function.
 */
void spi_bus_lock_set_bg_control(spi_bus_lock_handle_t lock, bg_ctrl_func_t bg_enable,
                                 bg_ctrl_func_t bg_disable, void *arg);

/**
 * Attach a device onto an SPI bus lock. The returning handle is used to perform
 * following requests for the attached device.
 *
 * @param lock SPI bus lock to attach
 * @param out_dev_handle Output handle corresponding to the device
 * @param flags requirement of the device, bitwise OR of SPI_BUS_LOCK_FLAG_* flags
 *
 * @return
 *  - ESP_ERR_NOT_SUPPORTED: if there's no hardware resources for new devices.
 *  - ESP_ERR_NO_MEM: if memory exhausted
 *  - ESP_OK: if success
 */
esp_err_t spi_bus_lock_register_dev(spi_bus_lock_handle_t lock,
                                    spi_bus_lock_dev_config_t *config,
                                    spi_bus_lock_dev_handle_t *out_dev_handle);

/**
 * Detach a device from its bus and free the resources used
 *
 * @param dev_handle Handle to the device.
 */
void spi_bus_lock_unregister_dev(spi_bus_lock_dev_handle_t dev_handle);

/**
 * @brief Get the parent bus lock of the device
 *
 * @param dev_handle Handle to the device to get bus lock
 * @return The bus lock handle
 */
spi_bus_lock_handle_t spi_bus_lock_get_parent(spi_bus_lock_dev_handle_t dev_handle);

/**
 * @brief Get the device ID of a lock.
 *
 * The callers should allocate CS pins according to this ID.
 *
 * @param dev_handle Handle to the device to get ID
 * @return ID of the device
 */
int spi_bus_lock_get_dev_id(spi_bus_lock_dev_handle_t dev_handle);

/**
 * @brief The device request to touch bus registers. Can only be called by the acquiring processor.
 *
 * Also check if the registers has been touched by other devices.
 *
 * @param dev_handle Handle to the device to operate the registers
 * @return true if there has been other devices touching SPI registers.
 *     The caller may need to do a full-configuration. Otherwise return
 *     false.
 */
bool spi_bus_lock_touch(spi_bus_lock_dev_handle_t dev_handle);

/************* Acquiring service *********************/
/**
 * Acquiring the SPI bus for exclusive use. Will also wait for the BG to finish all requests of
 * this device before it returns.
 *
 * After successfully return, the caller becomes the acquiring processor.
 *
 * @note For the main flash bus, `bg_disable` will be called to disable the cache.
 *
 * @param dev_handle Handle to the device request for acquiring.
 * @param wait Time to wait until timeout or succeed, must be `portMAX_DELAY` for now.
 * @return
 *  - ESP_OK: on success
 *  - ESP_ERR_INVALID_ARG: timeout is not portMAX_DELAY
 */
esp_err_t spi_bus_lock_acquire_start(spi_bus_lock_dev_handle_t dev_handle, TickType_t wait);

/**
 * Release the bus acquired. Will pass the acquiring processor to other blocked
 * processors (tasks or ISR), and cause them to be unblocked or invoked.
 *
 * The acquiring device may also become NULL if no device is asking for acquiring.
 * In this case, the BG may be invoked if there is any BG requests.
 *
 * If the new acquiring device has BG requests, the BG will be invoked before the
 * task is resumed later after the BG finishes all requests of the new acquiring
 * device. Otherwise the task of the new acquiring device will be resumed immediately.
 *
 * @param dev_handle Handle to the device releasing the bus.
 * @return
 *  - ESP_OK: on success
 *  - ESP_ERR_INVALID_STATE: the device hasn't acquired the lock yet
 */
esp_err_t spi_bus_lock_acquire_end(spi_bus_lock_dev_handle_t dev_handle);

/**
 * Get the device acquiring the bus.
 *
 * @note Return value is not stable as the acquiring processor may change
 *       when this function is called.
 *
 * @param lock Lock of SPI bus to get the acquiring device.
 * @return The argument corresponding to the acquiring device, see
 *         `spi_bus_lock_register_dev`.
 */
spi_bus_lock_dev_handle_t spi_bus_lock_get_acquiring_dev(spi_bus_lock_handle_t lock);

/************* BG (Background, for ISR or cache) service *********************/
/**
 * Call by a device to request a BG operation.
 *
 * Depending on the bus lock state, the BG operations may be resumed by this
 * call, or pending until BG operations allowed.
 *
 * Cleared by `spi_bus_lock_bg_clear_req` in the BG.
 *
 * @param dev_handle The device requesting BG operations.
 * @return always ESP_OK
 */
esp_err_t spi_bus_lock_bg_request(spi_bus_lock_dev_handle_t dev_handle);

/**
 * Wait until the ISR has finished all the BG operations for the acquiring device.
 * If any `spi_bus_lock_bg_request` for this device has been called after
 * `spi_bus_lock_acquire_start`, this function must be called before any operation
 * in the task.
 *
 * @note Can only be called when bus acquired by this device.
 *
 * @param dev_handle Handle to the device acquiring the bus.
 * @param wait Time to wait until timeout or succeed, must be `portMAX_DELAY` for now.
 * @return
 *  - ESP_OK: on success
 *  - ESP_ERR_INVALID_STATE: The device is not the acquiring bus.
 *  - ESP_ERR_INVALID_ARG: Timeout is not portMAX_DELAY.
 */
esp_err_t spi_bus_lock_wait_bg_done(spi_bus_lock_dev_handle_t dev_handle, TickType_t wait);

/**
 * Handle interrupt and closure of last operation. Should be called at the beginning of the ISR,
 * when the ISR is acting as the acquiring processor.
 *
 * @param lock The SPI bus lock
 *
 * @return false if the ISR has already touched the HW, should run closure of the
 *         last operation first; otherwise true if the ISR just start operating
 *         on the HW, closure should be skipped.
 */
bool spi_bus_lock_bg_entry(spi_bus_lock_handle_t lock);

/**
 * Handle the scheduling of other acquiring devices, and control of HW operation
 * status.
 *
 * If no BG request is found, call with `wip=false`. This function will return false,
 * indicating there is incoming BG requests for the current acquiring device (or
 * for all devices if there is no acquiring device) and the ISR needs retry.
 * Otherwise may schedule a new acquiring processor (unblock the task) if there
 * is, and return true.
 *
 * Otherwise if a BG request is started in this ISR, call with `wip=true` and the
 * function will enable the interrupt to make the ISR be called again when the
 * request is done.
 *
 * This function is safe and should still be called when the ISR just lost its acquiring processor
 * role, but hasn't quit.
 *
 * @note This function will not change acquiring device. The ISR call
 *       `spi_bus_lock_bg_update_acquiring` to check for new acquiring device,
 *       when acquiring devices need to be served before other devices.
 *
 * @param lock The SPI bus lock.
 * @param wip Whether an operation is being executed when quitting the ISR.
 * @param do_yield[out] Not touched when no yielding required, otherwise set
 *                      to pdTRUE.
 * @return false if retry is required, indicating that there is pending BG request.
 *         otherwise true and quit ISR is allowed.
 */
bool spi_bus_lock_bg_exit(spi_bus_lock_handle_t lock, bool wip, BaseType_t* do_yield);

/**
 * Check whether there is device asking for the acquiring device, and the desired
 * device for the next operation is also recommended.
 *
 * @note Must be called when the ISR is acting as the acquiring processor, and
 *        there is no acquiring device.
 *
 * @param lock The SPI bus lock.
 * @param out_dev_lock The recommended device for hte next operation. It's the new
 *        acquiring device when found, otherwise a device that has active BG request.
 *
 * @return true if the ISR need to quit (new acquiring device has no active BG
 *         request, or no active BG requests for all devices when there is no
 *         acquiring device), otherwise false.
 */
bool spi_bus_lock_bg_check_dev_acq(spi_bus_lock_handle_t lock, spi_bus_lock_dev_handle_t *out_dev_lock);

/**
 * Check if the device has BG requests. Must be called when the ISR is acting as
 * the acquiring processor.
 *
 * @note This is not stable, may become true again when a task request for BG
 *       operation (by `spi_bus_lock_bg_request`).
 *
 * @param dev_lock The device to check.
 * @return true if the device has BG requests, otherwise false.
 */
bool spi_bus_lock_bg_check_dev_req(spi_bus_lock_dev_handle_t dev_lock);

/**
 * Clear the pending BG operation request of a device after served. Must be
 * called when the ISR is acting as the acquiring processor.
 *
 * @note When the return value is true, the ISR will lost the acquiring processor role. Then
 *       `spi_bus_lock_bg_exit` must be called and checked before calling all other functions that
 *       require to be called when the ISR is the acquiring processor again.
 *
 * @param dev_handle The device whose request is served.
 * @return True if no pending requests for the acquiring device, or for all devices
 *         if there is no acquiring device. Otherwise false. When the return value is
 *         true, the ISR is no longer the acquiring processor.
 */
bool spi_bus_lock_bg_clear_req(spi_bus_lock_dev_handle_t dev_lock);

/**
 * Check if there is any active BG requests.
 *
 * @param lock The SPI bus lock.
 * @return true if any device has active BG requst, otherwise false.
 */
bool spi_bus_lock_bg_req_exist(spi_bus_lock_handle_t lock);

/*******************************************************************************
 * Variable and APIs for the OS to initialize the locks for the main chip
 ******************************************************************************/
/// The lock for the main bus
extern const spi_bus_lock_handle_t g_main_spi_bus_lock;

/**
 * @brief Initialize the main SPI bus, called during chip startup.
 *
 * @return always ESP_OK
 */
esp_err_t spi_bus_lock_init_main_bus(void);

/// The lock for the main flash device
extern const spi_bus_lock_dev_handle_t g_spi_lock_main_flash_dev;

/**
 * @brief Initialize the main flash device, called during chip startup.
 *
 * @return
 *      - ESP_OK: if success
 *      - ESP_ERR_NO_MEM: memory exhausted
 */
esp_err_t spi_bus_lock_init_main_dev(void);


#ifdef __cplusplus
}
#endif