sw/device/lib/dif/dif_spi_device.h

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

#ifndef OPENTITAN_SW_DEVICE_LIB_DIF_DIF_SPI_DEVICE_H_
#define OPENTITAN_SW_DEVICE_LIB_DIF_DIF_SPI_DEVICE_H_

/**
 * @file
 * @brief <a href="/hw/ip/spi_device/doc/">SPI Device</a> Device Interface
 * Functions
 */

#include <stddef.h>
#include <stdint.h>

#include "sw/device/lib/base/mmio.h"
#include "sw/device/lib/dif/dif_warn_unused_result.h"

#ifdef __cplusplus
extern "C" {
#endif  // __cplusplus

/**
 * A signal edge type: positive or negative.
 */
typedef enum dif_spi_device_edge {
  /**
   * Represents a positive edge (i.e., from low to high).
   */
  kDifSpiDeviceEdgePositive,
  /**
   * Represents a negative edge (i.e., from high to low).
   */
  kDifSpiDeviceEdgeNegative,
} dif_spi_device_edge_t;

/**
 * A bit ordering within a byte.
 */
typedef enum dif_spi_device_bit_order {
  /**
   * Represents the most-significant-bit to least-significant-bit order.
   */
  kDifSpiDeviceBitOrderMsbToLsb,
  /**
   * Represents the least-significant-bit to most-significant-bit order.
   */
  kDifSpiDeviceBitOrderLsbToMsb,
} dif_spi_device_bit_order_t;

/**
 * A toggle state: enabled, or disabled.
 *
 * This enum may be used instead of a `bool` when describing an enabled/disabled
 * state.
 */
typedef enum dif_spi_device_toggle {
  /*
   * The "enabled" state.
   */
  kDifSpiDeviceToggleEnabled,
  /**
   * The "disabled" state.
   */
  kDifSpiDeviceToggleDisabled,
} dif_spi_device_toggle_t;

/**
 * Hardware instantiation parameters for SPI.
 *
 * This struct describes information about the underlying hardware that is
 * not determined until the hardware design is used as part of a top-level
 * design.
 */
typedef struct dif_spi_device_params {
  /**
   * The base address for the SPI hardware registers.
   */
  mmio_region_t base_addr;
} dif_spi_device_params_t;

/**
 * Runtime configuration for SPI.
 *
 * This struct describes runtime information for one-time configuration of the
 * hardware.
 */
typedef struct dif_spi_device_config {
  dif_spi_device_edge_t clock_polarity;
  dif_spi_device_edge_t data_phase;
  dif_spi_device_bit_order_t tx_order;
  dif_spi_device_bit_order_t rx_order;
  uint8_t rx_fifo_timeout;
  /**
   * The length, in bytes, that should be reserved for the RX FIFO.
   *
   * `kDifSpiDeviceBufferLen / 2` is a good default for this value.
   */
  uint16_t rx_fifo_len;
  /**
   * The length, in bytes, that should be reserved for the TX FIFO.
   *
   * `kDifSpiDeviceBufferLen / 2` is a good default for this value.
   */
  uint16_t tx_fifo_len;
} dif_spi_device_config_t;

/**
 * A handle to a SPI device.
 *
 * This type should be treated as opaque by users.
 */
typedef struct dif_spi_device {
  dif_spi_device_params_t params;
  uint16_t rx_fifo_len;
  uint16_t tx_fifo_len;
} dif_spi_device_t;

/**
 * The result of a SPI operation.
 */
typedef enum dif_spi_device_result {
  /**
   * Indicates that the operation succeeded.
   */
  kDifSpiDeviceOk = 0,
  /**
   * Indicates some unspecified failure.
   */
  kDifSpiDeviceError = 1,
  /**
   * Indicates that some parameter passed into a function failed a
   * precondition.
   *
   * When this value is returned, no hardware operations occurred.
   */
  kDifSpiDeviceBadArg = 2,
} dif_spi_device_result_t;

/**
 * A SPI interrupt request type.
 */
typedef enum dif_spi_device_irq {
  /**
   * Indicates that the RX FIFO is full.
   */
  kDifSpiDeviceIrqRxFull,
  /**
   * Indicates that the RX FIFO is above the configured level.
   */
  kDifSpiDeviceIrqRxAboveLevel,
  /**
   * Indicates that the TX FIFO is below the configured level.
   */
  kDifSpiDeviceIrqTxBelowLevel,
  /**
   * Indicates an error in the RX FIFO.
   */
  kDifSpiDeviceIrqRxError,
  /**
   * Indicates that overflow has occurred in the RX FIFO.
   */
  kDifSpiDeviceIrqRxOverflow,
  /**
   * Indicates that underflow has occurred in the RX FIFO.
   */
  kDifSpiDeviceIrqTxUnderflow,
} dif_spi_device_irq_t;

/**
 * A snapshot of the enablement state of the interrupts for SPI.
 *
 * This is an opaque type, to be used with the
 * `dif_spi_device_irq_disable_all()` and
 * `dif_spi_device_irq_restore_all()` functions.
 */
typedef uint32_t dif_spi_device_irq_snapshot_t;

/**
 * The length of the SPI device FIFO buffer, in bytes.
 *
 * Useful for initializing FIFO lengths: for example, for equally-sized FIFOs,
 * `rx_fifo_len` and `tx_fifo_len` would be set to `kDifSpiDeviceBufferLen / 2`.
 */
extern const uint16_t kDifSpiDeviceBufferLen;

/**
 * Creates a new handle for SPI.
 *
 * This function does not actuate the hardware.
 *
 * @param params Hardware instantiation parameters.
 * @param[out] spi Out param for the initialized handle.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_init(dif_spi_device_params_t params,
                                            dif_spi_device_t *spi);

/**
 * Configures SPI with runtime information.
 *
 * This function should need to be called once for the lifetime of `handle`.
 *
 * @param spi A SPI handle.
 * @param config Runtime configuration parameters.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_configure(
    dif_spi_device_t *spi, dif_spi_device_config_t config);

/**
 * Issues an "abort" to the given SPI device, causing all in-progress IO to
 * halt.
 *
 * @param spi A SPI handle.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_abort(const dif_spi_device_t *spi);

/**
 * Returns whether a particular interrupt is currently pending.
 *
 * @param spi A SPI handle.
 * @param irq An interrupt type.
 * @param[out] is_pending Out-param for whether the interrupt is pending.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_is_pending(
    const dif_spi_device_t *spi, dif_spi_device_irq_t irq, bool *is_pending);

/**
 * Acknowledges a particular interrupt, indicating to the hardware that it has
 * been successfully serviced.
 *
 * @param spi A SPI handle.
 * @param irq An interrupt type.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_acknowledge(
    const dif_spi_device_t *spi, dif_spi_device_irq_t irq);

/**
 * Checks whether a particular interrupt is currently enabled or disabled.
 *
 * @param spi A SPI handle.
 * @param irq An interrupt type.
 * @param[out] state Out-param toggle state of the interrupt.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_get_enabled(
    const dif_spi_device_t *spi, dif_spi_device_irq_t irq,
    dif_spi_device_toggle_t *state);

/**
 * Sets whether a particular interrupt is currently enabled or disabled.
 *
 * @param spi A SPI handle.
 * @param irq An interrupt type.
 * @param state The new toggle state for the interrupt.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_set_enabled(
    const dif_spi_device_t *spi, dif_spi_device_irq_t irq,
    dif_spi_device_toggle_t state);

/**
 * Forces a particular interrupt, causing it to be serviced as if hardware had
 * asserted it.
 *
 * @param spi A SPI handle.
 * @param irq An interrupt type.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_force(const dif_spi_device_t *spi,
                                                 dif_spi_device_irq_t irq);

/**
 * Disables all interrupts, optionally snapshotting all toggle state for later
 * restoration.
 *
 * @param spi A SPI handle.
 * @param[out] snapshot Out-param for the snapshot; may be `NULL`.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_disable_all(
    const dif_spi_device_t *spi, dif_spi_device_irq_snapshot_t *snapshot);

/**
 * Restores interrupts from the given snapshot.
 *
 * This function can be used with `dif_spi_device_irq_disable_all()` to
 * temporary
 * interrupt save-and-restore.
 *
 * @param spi A SPI handle.
 * @param snapshot A snapshot to restore from.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_irq_restore_all(
    const dif_spi_device_t *spi, const dif_spi_device_irq_snapshot_t *snapshot);

/**
 * Sets up the "FIFO level" (that is, number of bytes present in a particular
 * FIFO) at which the TxLevel and RxLevel IRQs will fire.
 *
 * For the reciept side, when the FIFO overflows `rx_level` (i.e., goes over
 * the set level), an interrupt is fired. This can be used to detect that more
 * data should be read from the RX FIFO. This is the
 * `Spi Buffer -> Main Memory` case.
 *
 * Conversely, for the transmission side, when the FIFO underflows `tx_level`
 * (i.e., goes below the set level), an interrupt is fired. This can be used
 * to detect that there is free space to write more data to the TX FIFO.
 * This is the `Main Memory -> Spi Buffer` case.
 *
 * @param spi A SPI handle.
 * @param rx_level The new RX level, as described above.
 * @param tx_level The new TX level, as described above.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_set_irq_levels(
    const dif_spi_device_t *spi, uint16_t rx_level, uint16_t tx_level);

/**
 * Returns the number of bytes still pending receipt by software in the RX FIFO.
 *
 * @param spi A SPI handle.
 * @param[out] bytes_pending The number of bytes pending
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_rx_pending(const dif_spi_device_t *spi,
                                                  size_t *bytes_pending);

/**
 * Returns the number of bytes still pending transmission by hardware in the TX
 * FIFO.
 *
 * @param spi A SPI handle.
 * @param[out] bytes_pending The number of bytes pending
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_tx_pending(const dif_spi_device_t *spi,
                                                  size_t *bytes_pending);

/**
 * Reads at most `buf_len` bytes from the RX FIFO; the number of bytes read
 * will be written to `bytes_received`.
 *
 * @param spi A SPI device.
 * @param[out] buf A pointer to valid memory.
 * @param buf_len The length of the buffer `buf` points to.
 * @param[out] bytes_received The number of bytes successfully read; may be
 * null.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_recv(const dif_spi_device_t *spi,
                                            void *buf, size_t buf_len,
                                            size_t *bytes_received);

/**
 * Writes at most `buf_len` bytes to the TX FIFO; the number of bytes actually
 * written will be written to `bytes_sent`.
 *
 * @param spi A SPI device.
 * @param buf A pointer to bytes to be written.
 * @param buf_len The length of the buffer `buf` points to.
 * @param[out] bytes_sent The number of bytes successfully written; may be null.
 * @return The result of the operation.
 */
DIF_WARN_UNUSED_RESULT
dif_spi_device_result_t dif_spi_device_send(const dif_spi_device_t *spi,
                                            const void *buf, size_t buf_len,
                                            size_t *bytes_sent);

#ifdef __cplusplus
}  // extern "C"
#endif  // __cplusplus

#endif  // OPENTITAN_SW_DEVICE_LIB_DIF_DIF_SPI_DEVICE_H_