PHY status API for ethernet drivers (#8784)

* PHY status API for W5500 & ENC28J60 drivers
* move linkStatus() from ArduinoEthernet:: to LwipIntfDev::
* LwipIntfDev: include PHY status into ::connected()

libraries/lwIP_enc28j60/src/utility/enc28j60.cpp

@@ -106,6 +106,7 @@ void serial_printf(const char* fmt, ...)
 #define MACONX_BANK 0x02
 
 #define MACON1 0x00
+#define MACSTAT1 0x01
 #define MACON3 0x02
 #define MACON4 0x03
 #define MABBIPG 0x04
@@ -113,6 +114,16 @@ void serial_printf(const char* fmt, ...)
 #define MAIPGH 0x07
 #define MAMXFLL 0x0a
 #define MAMXFLH 0x0b
+#define MACON2 0x10
+#define MACSTAT2 0x11
+#define MICMD 0x12
+#define MIREGADR 0x14
+#define MIRDL 0x18
+#define MIRDH 0x19
+
+/* MICMD Register Bit Definitions */
+#define MICMD_MIISCAN 0x02
+#define MICMD_MIIRD 0x01
 
 #define MACON1_TXPAUS 0x08
 #define MACON1_RXPAUS 0x04
@@ -135,6 +146,9 @@ void serial_printf(const char* fmt, ...)
 #define MISTAT 0x0a
 #define EREVID 0x12
 
+/* MISTAT Register Bit Definitions */
+#define MISTAT_BUSY 0x01
+
 #define EPKTCNT_BANK 0x01
 #define ERXFCON 0x18
 #define EPKTCNT 0x19
@@ -720,3 +734,26 @@ uint16_t ENC28J60::readFrameData(uint8_t* buffer, uint16_t framesize)
 
     return _len;
 }
+
+uint16_t ENC28J60::phyread(uint8_t reg)
+{
+    // ( https://github.com/JAndrassy/EthernetENC/tree/master/src/utility/enc28j60.h )
+
+    setregbank(MACONX_BANK);
+    writereg(MIREGADR, reg);
+    writereg(MICMD, MICMD_MIIRD);
+    // wait until the PHY read completes
+    while (readreg(MISTAT) & MISTAT_BUSY)
+    {
+        delayMicroseconds(15);
+    }
+    writereg(MICMD, 0);
+    return (readreg(MIRDL) | readreg(MIRDH) << 8);
+}
+
+bool ENC28J60::isLinked()
+{
+    // ( https://github.com/JAndrassy/EthernetENC/tree/master/src/utility/enc28j60.h )
+
+    return !!(phyread(MACSTAT2) & 0x400);
+}

libraries/lwIP_enc28j60/src/utility/enc28j60.h

@@ -79,6 +79,21 @@ public:
     */
     virtual uint16_t readFrame(uint8_t* buffer, uint16_t bufsize);
 
+    /**
+        Check physical link
+        @return true when physical link is up
+    */
+    bool isLinked();
+
+    /**
+        Report whether ::isLinked() API is implemented
+        @return true when ::isLinked() API is implemented
+    */
+    constexpr bool isLinkDetectable() const
+    {
+        return true;
+    }
+
 protected:
     static constexpr bool interruptIsPossible()
     {
@@ -133,6 +148,8 @@ private:
     // Previously defined in contiki/core/sys/clock.h
     void clock_delay_usec(uint16_t dt);
 
+    uint16_t phyread(uint8_t reg);
+
     uint8_t   _bank;
     int8_t    _cs;
     SPIClass& _spi;