1 /* 2 * Copyright (c) 2017-2018, ARM Limited and Contributors. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7 #include <assert.h> 8 #include <cassert.h> 9 #include <stdbool.h> 10 #include "sdei_private.h" 11 12 /* Aliases for SDEI handler states: 'R'unning, 'E'nabled, and re'G'istered */ 13 #define r_ 0 14 #define R_ (1u << SDEI_STATF_RUNNING) 15 16 #define e_ 0 17 #define E_ (1u << SDEI_STATF_ENABLED) 18 19 #define g_ 0 20 #define G_ (1u << SDEI_STATF_REGISTERED) 21 22 /* All possible composite handler states */ 23 #define reg_ (r_ | e_ | g_) 24 #define reG_ (r_ | e_ | G_) 25 #define rEg_ (r_ | E_ | g_) 26 #define rEG_ (r_ | E_ | G_) 27 #define Reg_ (R_ | e_ | g_) 28 #define ReG_ (R_ | e_ | G_) 29 #define REg_ (R_ | E_ | g_) 30 #define REG_ (R_ | E_ | G_) 31 32 #define MAX_STATES (REG_ + 1) 33 34 /* Invalid state */ 35 #define SDEI_STATE_INVALID ((sdei_state_t) (-1)) 36 37 /* No change in state */ 38 #define SDEI_STATE_NOP ((sdei_state_t) (-2)) 39 40 #define X___ SDEI_STATE_INVALID 41 #define NOP_ SDEI_STATE_NOP 42 43 /* Ensure special states don't overlap with valid ones */ 44 CASSERT(X___ > REG_, sdei_state_overlap_invalid); 45 CASSERT(NOP_ > REG_, sdei_state_overlap_nop); 46 47 /* 48 * SDEI handler state machine: refer to sections 6.1 and 6.1.2 of the SDEI v1.0 49 * specification (ARM DEN0054A). 50 * 51 * Not all calls contribute to handler state transition. This table is also used 52 * to validate whether a call is permissible at a given handler state: 53 * 54 * - X___ denotes a forbidden transition; 55 * - NOP_ denotes a permitted transition, but there's no change in state; 56 * - Otherwise, XXX_ gives the new state. 57 * 58 * DISP[atch] is a transition added for the implementation, but is not mentioned 59 * in the spec. 60 * 61 * Those calls that the spec mentions as can be made any time don't picture in 62 * this table. 63 */ 64 65 static const sdei_state_t sdei_state_table[MAX_STATES][DO_MAX] = { 66 /* 67 * Action: REG REL ENA DISA UREG ROUT CTX COMP COMPR DISP 68 * Notes: [3] [1] [3] [3][4] [2] 69 */ 70 /* Handler unregistered, disabled, and not running. This is the default state. */ 71 /* 0 */ [reg_] = { reG_, NOP_, X___, X___, X___, X___, X___, X___, X___, X___, }, 72 73 /* Handler unregistered and running */ 74 /* 4 */ [Reg_] = { X___, X___, X___, X___, X___, X___, NOP_, reg_, reg_, X___, }, 75 76 /* Handler registered */ 77 /* 1 */ [reG_] = { X___, X___, rEG_, NOP_, reg_, NOP_, X___, X___, X___, X___, }, 78 79 /* Handler registered and running */ 80 /* 5 */ [ReG_] = { X___, X___, REG_, NOP_, Reg_, X___, NOP_, reG_, reG_, X___, }, 81 82 /* Handler registered and enabled */ 83 /* 3 */ [rEG_] = { X___, X___, NOP_, reG_, reg_, X___, X___, X___, X___, REG_, }, 84 85 /* Handler registered, enabled, and running */ 86 /* 7 */ [REG_] = { X___, X___, NOP_, ReG_, Reg_, X___, NOP_, rEG_, rEG_, X___, }, 87 88 /* 89 * Invalid states: no valid transition would leave the handler in these 90 * states; and no transition from these states is possible either. 91 */ 92 93 /* 94 * Handler can't be enabled without being registered. I.e., XEg is 95 * impossible. 96 */ 97 /* 2 */ [rEg_] = { X___, X___, X___, X___, X___, X___, X___, X___, X___, X___, }, 98 /* 6 */ [REg_] = { X___, X___, X___, X___, X___, X___, X___, X___, X___, X___, }, 99 }; 100 101 /* 102 * [1] Unregister will always also disable the event, so the new state will have 103 * Xeg. 104 * [2] Event is considered for dispatch only when it's both registered and 105 * enabled. 106 * [3] Never causes change in state. 107 * [4] Only allowed when running. 108 */ 109 110 /* 111 * Given an action, transition the state of an event by looking up the state 112 * table above: 113 * 114 * - Return false for invalid transition; 115 * - Return true for valid transition that causes no change in state; 116 * - Otherwise, update state and return true. 117 * 118 * This function assumes that the caller holds necessary locks. If the 119 * transition has constrains other than the state table describes, the caller is 120 * expected to restore the previous state. See sdei_event_register() for 121 * example. 122 */ 123 bool can_sdei_state_trans(sdei_entry_t *se, sdei_action_t act) 124 { 125 sdei_state_t next; 126 127 assert(act < DO_MAX); 128 if (se->state >= MAX_STATES) { 129 WARN(" event state invalid: %x\n", se->state); 130 return false; 131 } 132 133 next = sdei_state_table[se->state][act]; 134 switch (next) { 135 case SDEI_STATE_INVALID: 136 return false; 137 138 case SDEI_STATE_NOP: 139 return true; 140 141 default: 142 /* Valid transition. Update state. */ 143 SDEI_LOG(" event state 0x%x => 0x%x\n", se->state, next); 144 se->state = next; 145 146 return true; 147 } 148 } 149