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/*
* Copyright (c) 2017-2018, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <assert.h>
#include <stdbool.h>
#include <lib/cassert.h>
#include "sdei_private.h"
/* Aliases for SDEI handler states: 'R'unning, 'E'nabled, and re'G'istered */
#define r_ 0U
#define R_ (1u << SDEI_STATF_RUNNING)
#define e_ 0U
#define E_ (1u << SDEI_STATF_ENABLED)
#define g_ 0U
#define G_ (1u << SDEI_STATF_REGISTERED)
/* All possible composite handler states */
#define reg_ (r_ | e_ | g_)
#define reG_ (r_ | e_ | G_)
#define rEg_ (r_ | E_ | g_)
#define rEG_ (r_ | E_ | G_)
#define Reg_ (R_ | e_ | g_)
#define ReG_ (R_ | e_ | G_)
#define REg_ (R_ | E_ | g_)
#define REG_ (R_ | E_ | G_)
#define MAX_STATES (REG_ + 1u)
/* Invalid state */
#define SDEI_STATE_INVALID ((sdei_state_t) (-1))
/* No change in state */
#define SDEI_STATE_NOP ((sdei_state_t) (-2))
#define X___ SDEI_STATE_INVALID
#define NOP_ SDEI_STATE_NOP
/* Ensure special states don't overlap with valid ones */
CASSERT(X___ > REG_, sdei_state_overlap_invalid);
CASSERT(NOP_ > REG_, sdei_state_overlap_nop);
/*
* SDEI handler state machine: refer to sections 6.1 and 6.1.2 of the SDEI v1.0
* specification (ARM DEN0054A).
*
* Not all calls contribute to handler state transition. This table is also used
* to validate whether a call is permissible at a given handler state:
*
* - X___ denotes a forbidden transition;
* - NOP_ denotes a permitted transition, but there's no change in state;
* - Otherwise, XXX_ gives the new state.
*
* DISP[atch] is a transition added for the implementation, but is not mentioned
* in the spec.
*
* Those calls that the spec mentions as can be made any time don't picture in
* this table.
*/
static const sdei_state_t sdei_state_table[MAX_STATES][DO_MAX] = {
/*
* Action: REG REL ENA DISA UREG ROUT CTX COMP COMPR DISP
* Notes: [3] [1] [3] [3][4] [2]
*/
/* Handler unregistered, disabled, and not running. This is the default state. */
/* 0 */ [reg_] = { reG_, NOP_, X___, X___, X___, X___, X___, X___, X___, X___, },
/* Handler unregistered and running */
/* 4 */ [Reg_] = { X___, X___, X___, X___, X___, X___, NOP_, reg_, reg_, X___, },
/* Handler registered */
/* 1 */ [reG_] = { X___, X___, rEG_, NOP_, reg_, NOP_, X___, X___, X___, X___, },
/* Handler registered and running */
/* 5 */ [ReG_] = { X___, X___, REG_, NOP_, Reg_, X___, NOP_, reG_, reG_, X___, },
/* Handler registered and enabled */
/* 3 */ [rEG_] = { X___, X___, NOP_, reG_, reg_, X___, X___, X___, X___, REG_, },
/* Handler registered, enabled, and running */
/* 7 */ [REG_] = { X___, X___, NOP_, ReG_, Reg_, X___, NOP_, rEG_, rEG_, X___, },
/*
* Invalid states: no valid transition would leave the handler in these
* states; and no transition from these states is possible either.
*/
/*
* Handler can't be enabled without being registered. I.e., XEg is
* impossible.
*/
/* 2 */ [rEg_] = { X___, X___, X___, X___, X___, X___, X___, X___, X___, X___, },
/* 6 */ [REg_] = { X___, X___, X___, X___, X___, X___, X___, X___, X___, X___, },
};
/*
* [1] Unregister will always also disable the event, so the new state will have
* Xeg.
* [2] Event is considered for dispatch only when it's both registered and
* enabled.
* [3] Never causes change in state.
* [4] Only allowed when running.
*/
/*
* Given an action, transition the state of an event by looking up the state
* table above:
*
* - Return false for invalid transition;
* - Return true for valid transition that causes no change in state;
* - Otherwise, update state and return true.
*
* This function assumes that the caller holds necessary locks. If the
* transition has constrains other than the state table describes, the caller is
* expected to restore the previous state. See sdei_event_register() for
* example.
*/
bool can_sdei_state_trans(sdei_entry_t *se, sdei_action_t act)
{
sdei_state_t next;
assert(act < DO_MAX);
if (se->state >= MAX_STATES) {
WARN(" event state invalid: %x\n", se->state);
return false;
}
next = sdei_state_table[se->state][act];
switch (next) {
case SDEI_STATE_INVALID:
return false;
case SDEI_STATE_NOP:
return true;
default:
/* Valid transition. Update state. */
SDEI_LOG(" event state 0x%x => 0x%x\n", se->state, next);
se->state = next;
return true;
}
}
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