Initial SCSI bus emulation.

devices/common/hwcomponent.h

@@ -39,6 +39,9 @@ enum HWCompType {
     ADB_HOST    = 1ULL << 12, /* ADB host   */
     ADB_DEV     = 1ULL << 13, /* ADB device */
     INT_CTRL    = 1ULL << 16, /* interrupt controller */
+    SCSI_BUS    = 1ULL << 20, /* SCSI bus */
+    SCSI_HOST   = 1ULL << 21, /* SCSI host adapter */
+    SCSI_DEV    = 1ULL << 22, /* SCSI device */
     SND_SERVER  = 1ULL << 31, /* host sound server */
 };
 

devices/common/scsi/scsi.h

@@ -0,0 +1,122 @@
+/*
+DingusPPC - The Experimental PowerPC Macintosh emulator
+Copyright (C) 2018-22 divingkatae and maximum
+                      (theweirdo)     spatium
+
+(Contact divingkatae#1017 or powermax#2286 on Discord for more info)
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+/** @file SCSI bus definitions. */
+
+#ifndef SCSI_H
+#define SCSI_H
+
+#include <devices/common/hwcomponent.h>
+
+#include <array>
+#include <cinttypes>
+#include <string>
+
+/** SCSI control signals.
+    Bit positions follow the MESH controller convention for easier mapping.
+ */
+enum {
+    SCSI_CTRL_IO  = 1 << 0,
+    SCSI_CTRL_CD  = 1 << 1,
+    SCSI_CTRL_MSG = 1 << 2,
+    SCSI_CTRL_ATN = 1 << 3,
+    SCSI_CTRL_ACK = 1 << 4,
+    SCSI_CTRL_REQ = 1 << 5,
+    SCSI_CTRL_SEL = 1 << 6,
+    SCSI_CTRL_BSY = 1 << 7,
+    SCSI_CTRL_RST = 1 << 8,
+};
+
+enum ScsiPhase : int {
+    BUS_FREE = 0,
+    ARBITRATION,
+    SELECTION,
+    RESELECTION,
+    RESET,
+};
+
+enum ScsiMsg : int {
+    CONFIRM_SEL = 1,
+    BUS_PHASE_CHANGE,
+};
+
+/** Standard SCSI bus timing values measured in ns. */
+#define BUS_SETTLE_DELAY    400
+#define BUS_FREE_DELAY      800
+#define BUS_CLEAR_DELAY     800
+#define ARB_DELAY           2400
+#define SEL_ABORT_TIME      200000
+#define SEL_TIME_OUT        250000000
+
+#define SCSI_MAX_DEVS   8
+
+class ScsiDevice : public HWComponent {
+public:
+    ScsiDevice()  = default;
+    ~ScsiDevice() = default;
+
+    virtual void notify(ScsiMsg msg_type, int param) = 0;
+
+private:
+    int scsi_id;
+};
+
+/** This class provides a higher level abstraction for the SCSI bus. */
+class ScsiBus : public HWComponent {
+public:
+    ScsiBus();
+    ~ScsiBus() = default;
+
+    // low-level control/status
+    void register_device(int id, ScsiDevice* dev_obj);
+    void assert_ctrl_line(int id, uint16_t mask);
+    void release_ctrl_line(int id, uint16_t mask);
+    void release_ctrl_lines(int id);
+    int current_phase() { return this->cur_phase; };
+
+    // high-level control/status
+    bool begin_arbitration(int id);
+    bool end_arbitration(int id);
+    bool begin_selection(int initiator_id, int target_id, bool atn);
+    void confirm_selection(int target_id);
+    bool end_selection(int initiator_id, int target_id);
+
+protected:
+    void change_bus_phase(int initiator_id);
+
+private:
+    std::string name;
+
+    // SCSI devices registered with this bus
+    std::array<ScsiDevice*, SCSI_MAX_DEVS> devices;
+
+    // per-device state of the control lines
+    uint16_t    dev_ctrl_lines[SCSI_MAX_DEVS];
+
+    uint16_t    ctrl_lines;
+    int         cur_phase;
+    int         arb_winner_id;
+    int         initiator_id;
+    int         target_id;
+    uint8_t     data_lines;
+};
+
+#endif // SCSI_H

devices/common/scsi/scsi_bus.cpp

@@ -0,0 +1,172 @@
+/*
+DingusPPC - The Experimental PowerPC Macintosh emulator
+Copyright (C) 2018-22 divingkatae and maximum
+                      (theweirdo)     spatium
+
+(Contact divingkatae#1017 or powermax#2286 on Discord for more info)
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+/** @file SCSI bus emulation. */
+
+#include <devices/common/hwcomponent.h>
+#include <devices/common/scsi/scsi.h>
+#include <loguru.hpp>
+
+#include <cinttypes>
+
+ScsiBus::ScsiBus()
+{
+    supports_types(HWCompType::SCSI_BUS);
+
+    for(int i = 0; i < SCSI_MAX_DEVS; i++) {
+        this->devices[i]        = nullptr;
+        this->dev_ctrl_lines[i] = 0;
+    }
+
+    this->ctrl_lines = 0; // all control lines released
+    this->data_lines = 0; // data lines released
+    this->arb_winner_id = -1;
+    this->initiator_id = -1;
+    this->target_id = -1;
+}
+
+void ScsiBus::register_device(int id, ScsiDevice* dev_obj)
+{
+    if (this->devices[id] != nullptr) {
+        ABORT_F("ScsiBus: device with ID %d already registered", id);
+    }
+
+    this->devices[id] = dev_obj;
+}
+
+void ScsiBus::change_bus_phase(int initiator_id)
+{
+    for (int i = 0; i < SCSI_MAX_DEVS; i++) {
+        if (i == initiator_id)
+            continue; // don't notify the initiator
+        if (this->devices[i] != nullptr) {
+            this->devices[i]->notify(ScsiMsg::BUS_PHASE_CHANGE, this->cur_phase);
+        }
+    }
+}
+
+void ScsiBus::assert_ctrl_line(int initiator_id, uint16_t mask)
+{
+    uint16_t new_state = 0xFFFFU & mask;
+
+    this->dev_ctrl_lines[initiator_id] = new_state;
+
+    if (new_state == this->ctrl_lines) {
+        return;
+    }
+
+    this->ctrl_lines = new_state;
+
+    if (new_state & SCSI_CTRL_RST) {
+        this->cur_phase = ScsiPhase::RESET;
+        change_bus_phase(initiator_id);
+    }
+}
+
+void ScsiBus::release_ctrl_line(int id, uint16_t mask)
+{
+    uint16_t new_state = 0;
+
+    this->dev_ctrl_lines[id] &= ~mask;
+
+    // OR control lines of all devices together
+    for (int i = 0; i < SCSI_MAX_DEVS; i++) {
+        new_state |= this->dev_ctrl_lines[i];
+    }
+
+    if (this->ctrl_lines & SCSI_CTRL_RST) {
+        if (!(new_state & SCSI_CTRL_RST)) {
+            this->ctrl_lines = new_state;
+            this->cur_phase = ScsiPhase::BUS_FREE;
+            change_bus_phase(id);
+        }
+    }
+}
+
+void ScsiBus::release_ctrl_lines(int id)
+{
+    this->release_ctrl_line(id, 0xFFFFUL);
+}
+
+bool ScsiBus::begin_arbitration(int initiator_id)
+{
+    if (this->cur_phase == ScsiPhase::BUS_FREE) {
+        this->data_lines |= 1 << initiator_id;
+        this->cur_phase = ScsiPhase::ARBITRATION;
+        change_bus_phase(initiator_id);
+        return true;
+    } else {
+        return false;
+    }
+}
+
+bool ScsiBus::end_arbitration(int initiator_id)
+{
+    int highest_id = -1;
+
+    // find the highest ID bit on the data lines
+    for (int id = 7; id >= 0; id--) {
+        if (this->data_lines & (1 << id)) {
+            highest_id = id;
+            break;
+        }
+    }
+
+    if (highest_id >= 0) {
+        this->arb_winner_id = highest_id;
+    }
+
+    return highest_id == initiator_id;
+}
+
+bool ScsiBus::begin_selection(int initiator_id, int target_id, bool atn)
+{
+    // perform bus integrity checks
+    if (this->cur_phase != ScsiPhase::ARBITRATION || this->arb_winner_id != initiator_id)
+        return false;
+
+    this->data_lines |= (1 << initiator_id) | (1 << target_id);
+
+    if (atn) {
+        assert_ctrl_line(initiator_id, SCSI_CTRL_ATN);
+    }
+
+    this->initiator_id = initiator_id;
+    this->cur_phase = ScsiPhase::SELECTION;
+    change_bus_phase(initiator_id);
+    return true;
+}
+
+void ScsiBus::confirm_selection(int target_id)
+{
+    this->target_id = target_id;
+
+    // notify initiator about selection confirmation from target
+    if (this->initiator_id >= 0) {
+        this->devices[this->initiator_id]->notify(ScsiMsg::CONFIRM_SEL, target_id);
+    }
+}
+
+bool ScsiBus::end_selection(int initiator_id, int target_id)
+{
+    // check for selection confirmation from target
+    return this->target_id == target_id;
+}