1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Bitbanged MDIO support. 4 * 5 * Author: Scott Wood <scottwood@freescale.com> 6 * Copyright (c) 2007 Freescale Semiconductor 7 * 8 * Based on CPM2 MDIO code which is: 9 * 10 * Copyright (c) 2003 Intracom S.A. 11 * by Pantelis Antoniou <panto@intracom.gr> 12 * 13 * 2005 (c) MontaVista Software, Inc. 14 * Vitaly Bordug <vbordug@ru.mvista.com> 15 */ 16 17 #include <linux/module.h> 18 #include <linux/mdio-bitbang.h> 19 #include <linux/types.h> 20 #include <linux/delay.h> 21 22 #define MDIO_READ 2 23 #define MDIO_WRITE 1 24 25 #define MDIO_C45 (1<<15) 26 #define MDIO_C45_ADDR (MDIO_C45 | 0) 27 #define MDIO_C45_READ (MDIO_C45 | 3) 28 #define MDIO_C45_WRITE (MDIO_C45 | 1) 29 30 #define MDIO_SETUP_TIME 10 31 #define MDIO_HOLD_TIME 10 32 33 /* Minimum MDC period is 400 ns, plus some margin for error. MDIO_DELAY 34 * is done twice per period. 35 */ 36 #define MDIO_DELAY 250 37 38 /* The PHY may take up to 300 ns to produce data, plus some margin 39 * for error. 40 */ 41 #define MDIO_READ_DELAY 350 42 43 /* MDIO must already be configured as output. */ 44 static void mdiobb_send_bit(struct mdiobb_ctrl *ctrl, int val) 45 { 46 const struct mdiobb_ops *ops = ctrl->ops; 47 48 ops->set_mdio_data(ctrl, val); 49 ndelay(MDIO_DELAY); 50 ops->set_mdc(ctrl, 1); 51 ndelay(MDIO_DELAY); 52 ops->set_mdc(ctrl, 0); 53 } 54 55 /* MDIO must already be configured as input. */ 56 static int mdiobb_get_bit(struct mdiobb_ctrl *ctrl) 57 { 58 const struct mdiobb_ops *ops = ctrl->ops; 59 60 ndelay(MDIO_DELAY); 61 ops->set_mdc(ctrl, 1); 62 ndelay(MDIO_READ_DELAY); 63 ops->set_mdc(ctrl, 0); 64 65 return ops->get_mdio_data(ctrl); 66 } 67 68 /* MDIO must already be configured as output. */ 69 static void mdiobb_send_num(struct mdiobb_ctrl *ctrl, u16 val, int bits) 70 { 71 int i; 72 73 for (i = bits - 1; i >= 0; i--) 74 mdiobb_send_bit(ctrl, (val >> i) & 1); 75 } 76 77 /* MDIO must already be configured as input. */ 78 static u16 mdiobb_get_num(struct mdiobb_ctrl *ctrl, int bits) 79 { 80 int i; 81 u16 ret = 0; 82 83 for (i = bits - 1; i >= 0; i--) { 84 ret <<= 1; 85 ret |= mdiobb_get_bit(ctrl); 86 } 87 88 return ret; 89 } 90 91 /* Utility to send the preamble, address, and 92 * register (common to read and write). 93 */ 94 static void mdiobb_cmd(struct mdiobb_ctrl *ctrl, int op, u8 phy, u8 reg) 95 { 96 const struct mdiobb_ops *ops = ctrl->ops; 97 int i; 98 99 ops->set_mdio_dir(ctrl, 1); 100 101 /* 102 * Send a 32 bit preamble ('1's) with an extra '1' bit for good 103 * measure. The IEEE spec says this is a PHY optional 104 * requirement. The AMD 79C874 requires one after power up and 105 * one after a MII communications error. This means that we are 106 * doing more preambles than we need, but it is safer and will be 107 * much more robust. 108 */ 109 110 for (i = 0; i < 32; i++) 111 mdiobb_send_bit(ctrl, 1); 112 113 /* send the start bit (01) and the read opcode (10) or write (01). 114 Clause 45 operation uses 00 for the start and 11, 10 for 115 read/write */ 116 mdiobb_send_bit(ctrl, 0); 117 if (op & MDIO_C45) 118 mdiobb_send_bit(ctrl, 0); 119 else 120 mdiobb_send_bit(ctrl, 1); 121 mdiobb_send_bit(ctrl, (op >> 1) & 1); 122 mdiobb_send_bit(ctrl, (op >> 0) & 1); 123 124 mdiobb_send_num(ctrl, phy, 5); 125 mdiobb_send_num(ctrl, reg, 5); 126 } 127 128 /* In clause 45 mode all commands are prefixed by MDIO_ADDR to specify the 129 lower 16 bits of the 21 bit address. This transfer is done identically to a 130 MDIO_WRITE except for a different code. To enable clause 45 mode or 131 MII_ADDR_C45 into the address. Theoretically clause 45 and normal devices 132 can exist on the same bus. Normal devices should ignore the MDIO_ADDR 133 phase. */ 134 static int mdiobb_cmd_addr(struct mdiobb_ctrl *ctrl, int phy, u32 addr) 135 { 136 unsigned int dev_addr = (addr >> 16) & 0x1F; 137 unsigned int reg = addr & 0xFFFF; 138 mdiobb_cmd(ctrl, MDIO_C45_ADDR, phy, dev_addr); 139 140 /* send the turnaround (10) */ 141 mdiobb_send_bit(ctrl, 1); 142 mdiobb_send_bit(ctrl, 0); 143 144 mdiobb_send_num(ctrl, reg, 16); 145 146 ctrl->ops->set_mdio_dir(ctrl, 0); 147 mdiobb_get_bit(ctrl); 148 149 return dev_addr; 150 } 151 152 static int mdiobb_read(struct mii_bus *bus, int phy, int reg) 153 { 154 struct mdiobb_ctrl *ctrl = bus->priv; 155 int ret, i; 156 157 if (reg & MII_ADDR_C45) { 158 reg = mdiobb_cmd_addr(ctrl, phy, reg); 159 mdiobb_cmd(ctrl, MDIO_C45_READ, phy, reg); 160 } else 161 mdiobb_cmd(ctrl, MDIO_READ, phy, reg); 162 163 ctrl->ops->set_mdio_dir(ctrl, 0); 164 165 /* check the turnaround bit: the PHY should be driving it to zero, if this 166 * PHY is listed in phy_ignore_ta_mask as having broken TA, skip that 167 */ 168 if (mdiobb_get_bit(ctrl) != 0 && 169 !(bus->phy_ignore_ta_mask & (1 << phy))) { 170 /* PHY didn't drive TA low -- flush any bits it 171 * may be trying to send. 172 */ 173 for (i = 0; i < 32; i++) 174 mdiobb_get_bit(ctrl); 175 176 return 0xffff; 177 } 178 179 ret = mdiobb_get_num(ctrl, 16); 180 mdiobb_get_bit(ctrl); 181 return ret; 182 } 183 184 static int mdiobb_write(struct mii_bus *bus, int phy, int reg, u16 val) 185 { 186 struct mdiobb_ctrl *ctrl = bus->priv; 187 188 if (reg & MII_ADDR_C45) { 189 reg = mdiobb_cmd_addr(ctrl, phy, reg); 190 mdiobb_cmd(ctrl, MDIO_C45_WRITE, phy, reg); 191 } else 192 mdiobb_cmd(ctrl, MDIO_WRITE, phy, reg); 193 194 /* send the turnaround (10) */ 195 mdiobb_send_bit(ctrl, 1); 196 mdiobb_send_bit(ctrl, 0); 197 198 mdiobb_send_num(ctrl, val, 16); 199 200 ctrl->ops->set_mdio_dir(ctrl, 0); 201 mdiobb_get_bit(ctrl); 202 return 0; 203 } 204 205 struct mii_bus *alloc_mdio_bitbang(struct mdiobb_ctrl *ctrl) 206 { 207 struct mii_bus *bus; 208 209 bus = mdiobus_alloc(); 210 if (!bus) 211 return NULL; 212 213 __module_get(ctrl->ops->owner); 214 215 bus->read = mdiobb_read; 216 bus->write = mdiobb_write; 217 bus->priv = ctrl; 218 219 return bus; 220 } 221 EXPORT_SYMBOL(alloc_mdio_bitbang); 222 223 void free_mdio_bitbang(struct mii_bus *bus) 224 { 225 struct mdiobb_ctrl *ctrl = bus->priv; 226 227 module_put(ctrl->ops->owner); 228 mdiobus_free(bus); 229 } 230 EXPORT_SYMBOL(free_mdio_bitbang); 231 232 MODULE_LICENSE("GPL v2"); 233