1!!! WARNING !!! 2 3This guide describes to the old way of doing things. No new Ethernet drivers 4should be implemented this way. All new drivers should be written against the 5U-Boot core driver model. See doc/driver-model/README.txt 6 7----------------------- 8 Ethernet Driver Guide 9----------------------- 10 11The networking stack in Das U-Boot is designed for multiple network devices 12to be easily added and controlled at runtime. This guide is meant for people 13who wish to review the net driver stack with an eye towards implementing your 14own ethernet device driver. Here we will describe a new pseudo 'APE' driver. 15 16------------------ 17 Driver Functions 18------------------ 19 20All functions you will be implementing in this document have the return value 21meaning of 0 for success and non-zero for failure. 22 23 ---------- 24 Register 25 ---------- 26 27When U-Boot initializes, it will call the common function eth_initialize(). 28This will in turn call the board-specific board_eth_init() (or if that fails, 29the cpu-specific cpu_eth_init()). These board-specific functions can do random 30system handling, but ultimately they will call the driver-specific register 31function which in turn takes care of initializing that particular instance. 32 33Keep in mind that you should code the driver to avoid storing state in global 34data as someone might want to hook up two of the same devices to one board. 35Any such information that is specific to an interface should be stored in a 36private, driver-defined data structure and pointed to by eth->priv (see below). 37 38So the call graph at this stage would look something like: 39board_init() 40 eth_initialize() 41 board_eth_init() / cpu_eth_init() 42 driver_register() 43 initialize eth_device 44 eth_register() 45 46At this point in time, the only thing you need to worry about is the driver's 47register function. The pseudo code would look something like: 48int ape_register(bd_t *bis, int iobase) 49{ 50 struct ape_priv *priv; 51 struct eth_device *dev; 52 struct mii_dev *bus; 53 54 priv = malloc(sizeof(*priv)); 55 if (priv == NULL) 56 return -ENOMEM; 57 58 dev = malloc(sizeof(*dev)); 59 if (dev == NULL) { 60 free(priv); 61 return -ENOMEM; 62 } 63 64 /* setup whatever private state you need */ 65 66 memset(dev, 0, sizeof(*dev)); 67 sprintf(dev->name, "APE"); 68 69 /* 70 * if your device has dedicated hardware storage for the 71 * MAC, read it and initialize dev->enetaddr with it 72 */ 73 ape_mac_read(dev->enetaddr); 74 75 dev->iobase = iobase; 76 dev->priv = priv; 77 dev->init = ape_init; 78 dev->halt = ape_halt; 79 dev->send = ape_send; 80 dev->recv = ape_recv; 81 dev->write_hwaddr = ape_write_hwaddr; 82 83 eth_register(dev); 84 85#ifdef CONFIG_PHYLIB 86 bus = mdio_alloc(); 87 if (!bus) { 88 free(priv); 89 free(dev); 90 return -ENOMEM; 91 } 92 93 bus->read = ape_mii_read; 94 bus->write = ape_mii_write; 95 mdio_register(bus); 96#endif 97 98 return 1; 99} 100 101The exact arguments needed to initialize your device are up to you. If you 102need to pass more/less arguments, that's fine. You should also add the 103prototype for your new register function to include/netdev.h. 104 105The return value for this function should be as follows: 106< 0 - failure (hardware failure, not probe failure) 107>=0 - number of interfaces detected 108 109You might notice that many drivers seem to use xxx_initialize() rather than 110xxx_register(). This is the old naming convention and should be avoided as it 111causes confusion with the driver-specific init function. 112 113Other than locating the MAC address in dedicated hardware storage, you should 114not touch the hardware in anyway. That step is handled in the driver-specific 115init function. Remember that we are only registering the device here, we are 116not checking its state or doing random probing. 117 118 ----------- 119 Callbacks 120 ----------- 121 122Now that we've registered with the ethernet layer, we can start getting some 123real work done. You will need five functions: 124 int ape_init(struct eth_device *dev, bd_t *bis); 125 int ape_send(struct eth_device *dev, volatile void *packet, int length); 126 int ape_recv(struct eth_device *dev); 127 int ape_halt(struct eth_device *dev); 128 int ape_write_hwaddr(struct eth_device *dev); 129 130The init function checks the hardware (probing/identifying) and gets it ready 131for send/recv operations. You often do things here such as resetting the MAC 132and/or PHY, and waiting for the link to autonegotiate. You should also take 133the opportunity to program the device's MAC address with the dev->enetaddr 134member. This allows the rest of U-Boot to dynamically change the MAC address 135and have the new settings be respected. 136 137The send function does what you think -- transmit the specified packet whose 138size is specified by length (in bytes). You should not return until the 139transmission is complete, and you should leave the state such that the send 140function can be called multiple times in a row. 141 142The recv function should process packets as long as the hardware has them 143readily available before returning. i.e. you should drain the hardware fifo. 144For each packet you receive, you should call the net_process_received_packet() function on it 145along with the packet length. The common code sets up packet buffers for you 146already in the .bss (net_rx_packets), so there should be no need to allocate your 147own. This doesn't mean you must use the net_rx_packets array however; you're 148free to call the net_process_received_packet() function with any buffer you wish. So the pseudo 149code here would look something like: 150int ape_recv(struct eth_device *dev) 151{ 152 int length, i = 0; 153 ... 154 while (packets_are_available()) { 155 ... 156 length = ape_get_packet(&net_rx_packets[i]); 157 ... 158 net_process_received_packet(&net_rx_packets[i], length); 159 ... 160 if (++i >= PKTBUFSRX) 161 i = 0; 162 ... 163 } 164 ... 165 return 0; 166} 167 168The halt function should turn off / disable the hardware and place it back in 169its reset state. It can be called at any time (before any call to the related 170init function), so make sure it can handle this sort of thing. 171 172The write_hwaddr function should program the MAC address stored in dev->enetaddr 173into the Ethernet controller. 174 175So the call graph at this stage would look something like: 176some net operation (ping / tftp / whatever...) 177 eth_init() 178 dev->init() 179 eth_send() 180 dev->send() 181 eth_rx() 182 dev->recv() 183 eth_halt() 184 dev->halt() 185 186-------------------------------- 187 CONFIG_PHYLIB / CONFIG_CMD_MII 188-------------------------------- 189 190If your device supports banging arbitrary values on the MII bus (pretty much 191every device does), you should add support for the mii command. Doing so is 192fairly trivial and makes debugging mii issues a lot easier at runtime. 193 194After you have called eth_register() in your driver's register function, add 195a call to mdio_alloc() and mdio_register() like so: 196 bus = mdio_alloc(); 197 if (!bus) { 198 free(priv); 199 free(dev); 200 return -ENOMEM; 201 } 202 203 bus->read = ape_mii_read; 204 bus->write = ape_mii_write; 205 mdio_register(bus); 206 207And then define the mii_read and mii_write functions if you haven't already. 208Their syntax is straightforward: 209 int mii_read(struct mii_dev *bus, int addr, int devad, int reg); 210 int mii_write(struct mii_dev *bus, int addr, int devad, int reg, 211 u16 val); 212 213The read function should read the register 'reg' from the phy at address 'addr' 214and return the result to its caller. The implementation for the write function 215should logically follow. 216