sw/device/lib/dif/dif_rv_plic.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_RV_PLIC_H_
#define OPENTITAN_SW_DEVICE_LIB_DIF_DIF_RV_PLIC_H_

/**
 * @file
 * @brief <a href="/hw/ip/rv_plic/doc/">PLIC</a> Device Interface Functions
 *
 * The PLIC should be largely compatible with the (currently draft) [RISC-V PLIC
 * specification][plic], but tailored for the OpenTitan rv_plic register
 * addresses. We intend to make the addresses compatible with the PLIC
 * specification in the near future.
 *
 * [plic]: https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc
 */

#include <stdbool.h>
#include <stdint.h>

#include "sw/device/lib/base/macros.h"
#include "sw/device/lib/base/mmio.h"

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

/**
 * A toggle state: enabled, or disabled.
 *
 * This enum may be used instead of a `bool` when describing an enabled/disabled
 * state.
 */
typedef enum dif_rv_plic_toggle {
  /*
   * The "enabled" state.
   */
  kDifRvPlicToggleEnabled,
  /**
   * The "disabled" state.
   */
  kDifRvPlicToggleDisabled,
} dif_rv_plic_toggle_t;

/**
 * Hardware instantiation parameters for PLIC.
 *
 * 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_rv_plic_params {
  /**
   * The base address for the PLIC hardware registers.
   */
  mmio_region_t base_addr;
} dif_rv_plic_params_t;

/**
 * A handle to PLIC.
 *
 * This type should be treated as opaque by users.
 */
typedef struct dif_rv_plic {
  dif_rv_plic_params_t params;
} dif_rv_plic_t;

/**
 * The result of a PLIC operation.
 */
typedef enum dif_rv_plic_result {
  /**
   * Indicates that the operation succeeded.
   */
  kDifRvPlicOk = 0,
  /**
   * Indicates some unspecified failure.
   */
  kDifRvPlicError = 1,
  /**
   * Indicates that some parameter passed into a function failed a
   * precondition.
   *
   * When this value is returned, no hardware operations occurred.
   */
  kDifRvPlicBadArg = 2,
} dif_rv_plic_result_t;

/**
 * The lowest interrupt priority.
 */
extern const uint32_t kDifRvPlicMinPriority;

/**
 * The highest interrupt priority.
 */
extern const uint32_t kDifRvPlicMaxPriority;

/**
 * A PLIC interrupt source identifier.
 *
 * This corresponds to a specific interrupt, and not the device it originates
 * from.
 *
 * This is an unsigned 32-bit value that is at least zero and is less than the
 * `NumSrc` instantiation parameter of the `rv_plic` device.
 *
 * The value 0 corresponds to "No Interrupt".
 */
typedef uint32_t dif_rv_plic_irq_id_t;

/**
 * A PLIC interrupt target.
 *
 * This corresponds to a specific system that can service an interrupt. In
 * OpenTitan's case, that is the Ibex core. If there were multiple cores in the
 * system, each core would have its own specific interrupt target ID.
 *
 * This is an unsigned 32-bit value that is at least 0 and is less than the
 * `NumTarget` instantiation parameter of the `rv_plic` device.
 */
typedef uint32_t dif_rv_plic_target_t;

/**
 * Creates a new handle for PLIC.
 *
 * This function does not actuate the hardware.
 *
 * @param params Hardware instantiation parameters.
 * @param[out] plic Out param for the initialized handle.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_init(dif_rv_plic_params_t params,
                                      dif_rv_plic_t *plic);

/**
 * Returns whether a particular interrupt is currently pending.
 *
 * @param plic A PLIC handle.
 * @param irq An interrupt type.
 * @param[out] is_pending Out-param for whether the interrupt is pending.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_is_pending(const dif_rv_plic_t *plic,
                                                dif_rv_plic_irq_id_t irq,
                                                bool *is_pending);

/**
 * Checks whether a particular interrupt is currently enabled or disabled.
 *
 * @param plic A PLIC handle.
 * @param irq An interrupt type.
 * @param target An interrupt target.
 * @param[out] state Out-param toggle state of the interrupt.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_get_enabled(const dif_rv_plic_t *plic,
                                                 dif_rv_plic_irq_id_t irq,
                                                 dif_rv_plic_target_t target,
                                                 dif_rv_plic_toggle_t *state);

/**
 * Sets whether a particular interrupt is currently enabled or disabled.
 *
 * This operation does not affect IRQ generation in `target`, which
 * must be configured in the corresponding peripheral itself.
 *
 * @param plic A PLIC handle.
 * @param irq An interrupt type.
 * @param target An interrupt target.
 * @param state The new toggle state for the interrupt.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_set_enabled(const dif_rv_plic_t *plic,
                                                 dif_rv_plic_irq_id_t irq,
                                                 dif_rv_plic_target_t target,
                                                 dif_rv_plic_toggle_t state);

/**
 * Sets IRQ source priority (0-3).
 *
 * In order for the PLIC to set a Claim/Complete register and assert the
 * external interrupt line to the target (Ibex, ...), the priority of the IRQ
 * source must be higher than the threshold for this source.
 *
 * @param plic A PLIC handle.
 * @param irq An interrupt type.
 * @param priority Priority to set.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_set_priority(const dif_rv_plic_t *plic,
                                                  dif_rv_plic_irq_id_t irq,
                                                  uint32_t priority);

/**
 * Sets the target priority threshold.
 *
 * Sets the target priority threshold. PLIC will only interrupt a target when
 * IRQ source priority is set higher than the priority threshold for the
 * corresponding target.
 *
 * @param plic A PLIC handle.
 * @param target Target to set the IRQ priority threshold for.
 * @param threshold IRQ priority threshold to be set.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_target_set_threshold(
    const dif_rv_plic_t *plic, dif_rv_plic_target_t target, uint32_t threshold);

/**
 * Claims an IRQ and gets the information about the source.
 *
 * Claims an IRQ and returns the IRQ related data to the caller. This function
 * reads a target specific Claim/Complete register. #dif_rv_plic_irq_complete
 * must be called in order to allow another interrupt with the same source id to
 * be delivered. This usually would be done once the interrupt has been
 * serviced.
 *
 * Another IRQ can be claimed before a prior IRQ is completed. In this way, this
 * functionality is compatible with nested interrupt handling. The restriction
 * is that you must Complete a Claimed IRQ before you will be able to claim an
 * IRQ with the same ID. This allows a pair of Claim/Complete calls to be
 * overlapped with another pair -- and there is no requirement that the
 * interrupts should be Completed in the reverse order of when they were
 * Claimed.
 *
 * @see #dif_rv_plic_irq_complete
 *
 * @param plic A PLIC handle.
 * @param target Target that claimed the IRQ.
 * @param[out] claim_data Data that describes the origin of the IRQ.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_claim(const dif_rv_plic_t *plic,
                                           dif_rv_plic_target_t target,
                                           dif_rv_plic_irq_id_t *claim_data);

/**
 * Completes the claimed IRQ.
 *
 * Finishes servicing of the claimed IRQ by writing the IRQ source ID back to a
 * target specific Claim/Complete register. This function must be called after
 * #dif_rv_plic_irq_claim, when the caller is prepared to service another IRQ
 * with the same source ID. If a source ID is never Completed, then when future
 * interrupts are Claimed, they will never have the source ID of the uncompleted
 * IRQ.
 *
 * @see #dif_rv_plic_irq_claim
 *
 * @param plic A PLIC handle.
 * @param target Target that claimed the IRQ.
 * @param complete_data Previously claimed IRQ data that is used to signal
 *        PLIC of the IRQ servicing completion.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_irq_complete(
    const dif_rv_plic_t *plic, dif_rv_plic_target_t target,
    dif_rv_plic_irq_id_t complete_data);

/**
 * Forces the software interrupt for a particular target.
 *
 * This function causes an interrupt to the `target` HART to be serviced as if
 * hardware had asserted it.
 *
 * This function allows to synchronise between the HARTs, which otherwise
 * would not be possible due to HART being only able to access own CSRs.
 * NOTE: this is not an issue on Ibex, as it has only one HART.
 *
 * An interrupt handler is expected to call
 * `dif_rv_plic_software_irq_acknowledge` when the interrupt has been handled.
 *
 * @param plic PLIC state data.
 * @param target Target HART.
 * @return `dif_rv_plic_result_t`.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_software_irq_force(
    const dif_rv_plic_t *plic, dif_rv_plic_target_t target);

/**
 * Acknowledges the software interrupt for a particular target.
 *
 * This function indicates to the hardware that the software interrupt has been
 * successfully serviced. It is expected to be called from a software interrupt
 * handler.
 *
 * @param plic PLIC state data.
 * @param target Target HART.
 * @return `dif_rv_plic_result_t`.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_software_irq_acknowledge(
    const dif_rv_plic_t *plic, dif_rv_plic_target_t target);

/**
 * Returns software interrupt pending state for a particular target.
 *
 * @param plic PLIC state data.
 * @param target Target HART.
 * @param[out] is_pending Flag indicating whether the interrupt is pending.
 * @return `dif_rv_plic_result_t`.
 */
OT_WARN_UNUSED_RESULT
dif_rv_plic_result_t dif_rv_plic_software_irq_is_pending(
    const dif_rv_plic_t *plic, dif_rv_plic_target_t target, bool *is_pending);

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

#endif  // OPENTITAN_SW_DEVICE_LIB_DIF_DIF_RV_PLIC_H_