bigmac: MAC serial EEPROM emulation.

devices/ethernet/bigmac.cpp

@@ -32,6 +32,7 @@ BigMac::BigMac(uint8_t id) {
     this->chip_id = id;
     this->phy_reset();
     this->mii_reset();
+    this->srom_reset();
 }
 
 uint16_t BigMac::read(uint16_t reg_offset) {
@@ -40,6 +41,8 @@ uint16_t BigMac::read(uint16_t reg_offset) {
         return this->chip_id;
     case BigMacReg::MIF_CSR:
         return (this->mif_csr_old & ~Mif_Data_In) | (this->mii_in_bit << 3);
+    case BigMacReg::SROM_CSR:
+        return (this->srom_csr_old & ~Srom_Data_In) | (this->srom_in_bit << 2);
     default:
         LOG_F(WARNING, "%s: unimplemented register at 0x%X", this->name.c_str(),
               reg_offset);
@@ -61,6 +64,16 @@ void BigMac::write(uint16_t reg_offset, uint16_t value) {
         }
         this->mif_csr_old = value;
         break;
+    case BigMacReg::SROM_CSR:
+        if (value & Srom_Chip_Select) {
+            // exchange data on each low-to-high transition of Srom_Clock
+            if (((this->srom_csr_old ^ value) & Srom_Clock) && (value & Srom_Clock))
+                this->srom_xmit_bit(!!(value & Srom_Data_Out));
+        } else {
+            this->srom_reset();
+        }
+        this->srom_csr_old = value;
+        break;
     default:
         LOG_F(WARNING, "%s: unimplemented register at 0x%X is written with 0x%X",
               this->name.c_str(), reg_offset, value);
@@ -247,6 +260,70 @@ void BigMac::phy_reg_write(uint8_t reg_num, uint16_t value) {
     }
 }
 
+// ======================== MAC Serial EEPROM emulation ========================
+void BigMac::srom_reset() {
+    this->srom_csr_old = 0;
+    this->srom_bit_counter = 0;
+    this->srom_opcode = 0;
+    this->srom_address = 0;
+    this->srom_state = Srom_Start;
+}
+
+bool BigMac::srom_rcv_value(uint16_t& var, uint8_t num_bits, uint8_t next_bit) {
+    var = (var << 1) | (next_bit & 1);
+    this->srom_bit_counter++;
+    if (this->srom_bit_counter >= num_bits) {
+        this->srom_bit_counter = 0;
+        return true; // all bits have been received -> return true
+    }
+    return false; // more bits expected
+}
+
+void BigMac::srom_xmit_bit(const uint8_t bit_val) {
+    switch(this->srom_state) {
+    case Srom_Start:
+        if (bit_val)
+            this->srom_state = Srom_Opcode;
+        else
+            this->srom_reset();
+        break;
+    case Srom_Opcode:
+        if (this->srom_rcv_value(this->srom_opcode, 2, bit_val)) {
+            switch(this->srom_opcode) {
+            case 2: // read
+                this->srom_state = Srom_Address;
+                break;
+            default:
+                LOG_F(ERROR, "%s: unsupported SROM opcode %d", this->name.c_str(),
+                      this->srom_opcode);
+                this->srom_reset();
+            }
+        }
+        break;
+    case Srom_Address:
+        if (this->srom_rcv_value(this->srom_address, 6, bit_val)) {
+            LOG_F(9, "SROM address received = 0x%X", this->srom_address);
+            this->srom_bit_counter = 16;
+            this->srom_state = Srom_Read_Data;
+        }
+        break;
+    case Srom_Read_Data:
+        if (this->srom_bit_counter) {
+            this->srom_bit_counter--;
+            this->srom_in_bit = (this->srom_data[this->srom_address] >> this->srom_bit_counter) & 1;
+            if (!this->srom_bit_counter) {
+                this->srom_address++;
+                this->srom_bit_counter = 16;
+            }
+        }
+        break;
+    default:
+        LOG_F(ERROR, "%s: unhandled state %d in srom_xmit_bit", this->name.c_str(),
+              this->srom_state);
+        this->srom_reset();
+    }
+}
+
 static const DeviceDescription BigMac_Heathrow_Descriptor = {
     BigMac::create_for_heathrow, {}, {}
 };

devices/ethernet/bigmac.h

@@ -37,8 +37,9 @@ enum EthernetCellId : uint8_t {
 
 /* BigMac HW registers. */
 enum BigMacReg : uint16_t {
-    CHIP_ID = 0x170,
-    MIF_CSR = 0x180,
+    CHIP_ID     = 0x170,
+    MIF_CSR     = 0x180,
+    SROM_CSR    = 0x190,
 };
 
 /* MIF_CSR bit definitions. */
@@ -49,6 +50,22 @@ enum {
     Mif_Data_In     = 1 << 3
 };
 
+/* SROM_CSR bit definitions. */
+enum {
+    Srom_Chip_Select = 1 << 0,
+    Srom_Clock       = 1 << 1,
+    Srom_Data_In     = 1 << 2,
+    Srom_Data_Out    = 1 << 3,
+};
+
+/* Serial EEPROM states (see ST93C46 datasheet). */
+enum {
+    Srom_Start,
+    Srom_Opcode,
+    Srom_Address,
+    Srom_Read_Data,
+};
+
 /* MII frame states. */
 enum MII_FRAME_SM {
     Preamble,
@@ -98,6 +115,11 @@ public:
     uint16_t phy_reg_read(uint8_t reg_num);
     void phy_reg_write(uint8_t reg_num, uint16_t value);
 
+    // MAC Serial EEPROM methods
+    void srom_reset();
+    bool srom_rcv_value(uint16_t& var, uint8_t num_bits, uint8_t next_bit);
+    void srom_xmit_bit(const uint8_t bit_val);
+
 private:
     uint8_t chip_id; // BigMac Chip ID
 
@@ -120,6 +142,16 @@ private:
     uint8_t         phy_rev;
     uint16_t        phy_bmcr;
     uint16_t        phy_anar;
+
+    // MAC SROM state
+    uint8_t         srom_csr_old = 0;
+    uint8_t         srom_bit_counter = 0;
+    uint16_t        srom_opcode = 0;
+    uint16_t        srom_address = 0;
+    uint8_t         srom_in_bit = 0;
+    uint8_t         srom_state = Srom_Start;
+    uint16_t        srom_data[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                                     0xDEAD, 0xBEEF, 0xBABE}; // bogus MAC!!!
 };
 
 #endif // BIG_MAC_H