Add SPD SDRAM emulation.

devices/spdram.h

@@ -0,0 +1,141 @@
+/*
+DingusPPC - The Experimental PowerPC Macintosh emulator
+Copyright (C) 2018-20 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 Serial presence detect (SPD) RAM module emulation.
+
+    Author: Max Poliakovski
+
+    @description
+    Serial presence detect (SPD) is a standard that prescribes an automatic way
+    to supply various information about a memory module.
+    A SPD-compatible memory module contains a small EEPROM that stores useful
+    information like memory size, configuration, speed, manufacturer etc.
+    The content depends on the module type.
+
+    This EEPROM is accessible via the I2C bus. The EEPROM I2C address will be
+    configured depending on the physical RAM slot the module is inserted to.
+
+    A 168-Pin SDRAM slot includes three specialized pins SA0-SA2 for setting
+    an unique I2C address for each module EEPROM. The SA0-SA2 pins are hardwired
+    differently for each RAM slot. Example:
+
+    Slot    SA0-SA2     I2C address
+    A       %000        0x50 + %000 = 0x50
+    B       %001        0x50 + %001 = 0x51
+
+    Further reading: https://en.wikipedia.org/wiki/Serial_presence_detect
+ */
+
+#ifndef SPD_EEPROM_H
+#define SPD_EEPROM_H
+
+#include <cinttypes>
+#include <string>
+#include <stdexcept>
+#include <thirdparty/loguru.hpp>
+#include "i2c.h"
+#include "hwcomponent.h"
+
+enum RAMType : int {
+    SDRAM = 4
+};
+
+
+class SpdSdram168 : public HWComponent, public I2CDevice {
+public:
+    SpdSdram168(uint8_t addr) {
+        this->dev_addr = addr;
+        this->pos = 0;
+    };
+
+    ~SpdSdram168() = default;
+
+    bool supports_type(HWCompType type) { return type == HWCompType::RAM; };
+
+    void set_capacity(int capacity_megs) {
+        switch(capacity_megs) {
+        case 32:
+            this->eeprom_data[3] = 0xC; /* 12 rows    */
+            this->eeprom_data[4] = 0x8; /* 8  columns */
+            this->eeprom_data[5] = 0x1; /* one bank   */
+            break;
+        case 64:
+            this->eeprom_data[3] = 0xC; /* 12 rows    */
+            this->eeprom_data[4] = 0x9; /* 9  columns */
+            this->eeprom_data[5] = 0x1; /* one bank   */
+            break;
+        case 128:
+            this->eeprom_data[3] = 0xC; /* 12 rows    */
+            this->eeprom_data[4] = 0xA; /* 10 columns */
+            this->eeprom_data[5] = 0x1; /* one bank   */
+            break;
+        case 256:
+            this->eeprom_data[3] = 0xC; /* 12 rows    */
+            this->eeprom_data[4] = 0xA; /* 10 columns */
+            this->eeprom_data[5] = 0x2; /* two banks  */
+            break;
+        default:
+            throw std::invalid_argument(std::string("Unsupported capacity!"));
+        }
+        LOG_F(INFO, "SDRAM capacity set to %dMB, I2C addr = 0x%X",
+            capacity_megs, this->dev_addr);
+    };
+
+    void start_transaction() { this->pos = 0; };
+
+    bool send_subaddress(uint8_t sub_addr) {
+        this->pos = sub_addr;
+        LOG_F(9, "SDRAM subaddress set to 0x%X", sub_addr);
+        return true;
+    };
+
+    bool send_byte(uint8_t data) {
+        LOG_F(9, "SDRAM byte 0x%X received", data);
+        return true;
+    };
+
+    bool receive_byte(uint8_t *p_data) {
+        if (this->pos >= this->eeprom_data[0]) {
+            this->pos = 0; /* attempt to read past SPD data should wrap around */
+        }
+        LOG_F(9, "SDRAM sending EEPROM byte 0x%X", this->eeprom_data[this->pos]);
+        *p_data = this->eeprom_data[this->pos++];
+        return true;
+    };
+
+private:
+    uint8_t dev_addr; /* I2C address */
+    int pos; /* actual read position */
+
+    /* EEPROM content */
+    uint8_t eeprom_data[256] = {
+        128, /* number of bytes present */
+        8,   /* log2(EEPROM size) */
+        RAMType::SDRAM, /* memory type */
+
+        /* the following fields will be set up in set_capacity() */
+        0, /* number of row addresses */
+        0, /* number of column addresses */
+        0 /* number of banks */
+    };
+};
+
+#endif /* SPD_EEPROM_H */

machines/machinegossamer.cpp

@@ -31,6 +31,22 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #include "devices/machineid.h"
 #include "devices/macio.h"
 #include "devices/viacuda.h"
+#include "devices/spdram.h"
+
+static void setup_ram_slot(std::string name, int i2c_addr, int capacity_megs)
+{
+    if (!capacity_megs)
+        return;
+
+    gMachineObj->add_component(name, new SpdSdram168(i2c_addr));
+    SpdSdram168 *ram_dimm = dynamic_cast<SpdSdram168 *>(gMachineObj->get_comp_by_name(name));
+    ram_dimm->set_capacity(capacity_megs);
+
+    /* register RAM DIMM with the I2C bus */
+    I2CBus *i2c_bus = dynamic_cast<I2CBus *>(gMachineObj->get_comp_by_type(HWCompType::I2C_HOST));
+    i2c_bus->register_device(i2c_addr, ram_dimm);
+}
+
 
 int create_gossamer()
 {
@@ -67,6 +83,11 @@ int create_gossamer()
         return -1;
     }
 
+    /* configure RAM slots */
+    setup_ram_slot("RAM_DIMM_1", 0x57,  64); /* RAM slot 1 ->  64MB by default */
+    setup_ram_slot("RAM_DIMM_2", 0x56,   0); /* RAM slot 2 -> empty by default */
+    setup_ram_slot("RAM_DIMM_3", 0x55,   0); /* RAM slot 3 -> empty by default */
+
     /* Init virtual CPU and request MPC750 CPU aka G3 */
     ppc_cpu_init(grackle_obj, PPC_VER::MPC750);