drivers/net/phy/mdio-bitbang.c

   1 /*
   2  * Bitbanged MDIO support.
   3  *
   4  * Author: Scott Wood <scottwood@freescale.com>
   5  * Copyright (c) 2007 Freescale Semiconductor
   6  *
   7  * Based on CPM2 MDIO code which is:
   8  *
   9  * Copyright (c) 2003 Intracom S.A.
  10  *  by Pantelis Antoniou <panto@intracom.gr>
  11  *
  12  * 2005 (c) MontaVista Software, Inc.
  13  * Vitaly Bordug <vbordug@ru.mvista.com>
  14  *
  15  * This file is licensed under the terms of the GNU General Public License
  16  * version 2. This program is licensed "as is" without any warranty of any
  17  * kind, whether express or implied.
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/mdio-bitbang.h>
  22 #include <linux/types.h>
  23 #include <linux/delay.h>
  24
  25 #define MDIO_READ 2
  26 #define MDIO_WRITE 1
  27
  28 #define MDIO_C45 (1<<15)
  29 #define MDIO_C45_ADDR (MDIO_C45 | 0)
  30 #define MDIO_C45_READ (MDIO_C45 | 3)
  31 #define MDIO_C45_WRITE (MDIO_C45 | 1)
  32
  33 #define MDIO_SETUP_TIME 10
  34 #define MDIO_HOLD_TIME 10
  35
  36 /* Minimum MDC period is 400 ns, plus some margin for error.  MDIO_DELAY
  37  * is done twice per period.
  38  */
  39 #define MDIO_DELAY 250
  40
  41 /* The PHY may take up to 300 ns to produce data, plus some margin
  42  * for error.
  43  */
  44 #define MDIO_READ_DELAY 350
  45
  46 /* MDIO must already be configured as output. */
  47 static void mdiobb_send_bit(struct mdiobb_ctrl *ctrl, int val)
  48 {
  49         const struct mdiobb_ops *ops = ctrl->ops;
  50
  51         ops->set_mdio_data(ctrl, val);
  52         ndelay(MDIO_DELAY);
  53         ops->set_mdc(ctrl, 1);
  54         ndelay(MDIO_DELAY);
  55         ops->set_mdc(ctrl, 0);
  56 }
  57
  58 /* MDIO must already be configured as input. */
  59 static int mdiobb_get_bit(struct mdiobb_ctrl *ctrl)
  60 {
  61         const struct mdiobb_ops *ops = ctrl->ops;
  62
  63         ndelay(MDIO_DELAY);
  64         ops->set_mdc(ctrl, 1);
  65         ndelay(MDIO_READ_DELAY);
  66         ops->set_mdc(ctrl, 0);
  67
  68         return ops->get_mdio_data(ctrl);
  69 }
  70
  71 /* MDIO must already be configured as output. */
  72 static void mdiobb_send_num(struct mdiobb_ctrl *ctrl, u16 val, int bits)
  73 {
  74         int i;
  75
  76         for (i = bits - 1; i >= 0; i--)
  77                 mdiobb_send_bit(ctrl, (val >> i) & 1);
  78 }
  79
  80 /* MDIO must already be configured as input. */
  81 static u16 mdiobb_get_num(struct mdiobb_ctrl *ctrl, int bits)
  82 {
  83         int i;
  84         u16 ret = 0;
  85
  86         for (i = bits - 1; i >= 0; i--) {
  87                 ret <<= 1;
  88                 ret |= mdiobb_get_bit(ctrl);
  89         }
  90
  91         return ret;
  92 }
  93
  94 /* Utility to send the preamble, address, and
  95  * register (common to read and write).
  96  */
  97 static void mdiobb_cmd(struct mdiobb_ctrl *ctrl, int op, u8 phy, u8 reg)
  98 {
  99         const struct mdiobb_ops *ops = ctrl->ops;
 100         int i;
 101
 102         ops->set_mdio_dir(ctrl, 1);
 103
 104         /*
 105          * Send a 32 bit preamble ('1's) with an extra '1' bit for good
 106          * measure.  The IEEE spec says this is a PHY optional
 107          * requirement.  The AMD 79C874 requires one after power up and
 108          * one after a MII communications error.  This means that we are
 109          * doing more preambles than we need, but it is safer and will be
 110          * much more robust.
 111          */
 112
 113         for (i = 0; i < 32; i++)
 114                 mdiobb_send_bit(ctrl, 1);
 115
 116         /* send the start bit (01) and the read opcode (10) or write (10).
 117            Clause 45 operation uses 00 for the start and 11, 10 for
 118            read/write */
 119         mdiobb_send_bit(ctrl, 0);
 120         if (op & MDIO_C45)
 121                 mdiobb_send_bit(ctrl, 0);
 122         else
 123                 mdiobb_send_bit(ctrl, 1);
 124         mdiobb_send_bit(ctrl, (op >> 1) & 1);
 125         mdiobb_send_bit(ctrl, (op >> 0) & 1);
 126
 127         mdiobb_send_num(ctrl, phy, 5);
 128         mdiobb_send_num(ctrl, reg, 5);
 129 }
 130
 131 /* In clause 45 mode all commands are prefixed by MDIO_ADDR to specify the
 132    lower 16 bits of the 21 bit address. This transfer is done identically to a
 133    MDIO_WRITE except for a different code. To enable clause 45 mode or
 134    MII_ADDR_C45 into the address. Theoretically clause 45 and normal devices
 135    can exist on the same bus. Normal devices should ignore the MDIO_ADDR
 136    phase. */
 137 static int mdiobb_cmd_addr(struct mdiobb_ctrl *ctrl, int phy, u32 addr)
 138 {
 139         unsigned int dev_addr = (addr >> 16) & 0x1F;
 140         unsigned int reg = addr & 0xFFFF;
 141         mdiobb_cmd(ctrl, MDIO_C45_ADDR, phy, dev_addr);
 142
 143         /* send the turnaround (10) */
 144         mdiobb_send_bit(ctrl, 1);
 145         mdiobb_send_bit(ctrl, 0);
 146
 147         mdiobb_send_num(ctrl, reg, 16);
 148
 149         ctrl->ops->set_mdio_dir(ctrl, 0);
 150         mdiobb_get_bit(ctrl);
 151
 152         return dev_addr;
 153 }
 154
 155 static int mdiobb_read(struct mii_bus *bus, int phy, int reg)
 156 {
 157         struct mdiobb_ctrl *ctrl = bus->priv;
 158         int ret, i;
 159
 160         if (reg & MII_ADDR_C45) {
 161                 reg = mdiobb_cmd_addr(ctrl, phy, reg);
 162                 mdiobb_cmd(ctrl, MDIO_C45_READ, phy, reg);
 163         } else
 164                 mdiobb_cmd(ctrl, MDIO_READ, phy, reg);
 165
 166         ctrl->ops->set_mdio_dir(ctrl, 0);
 167
 168         /* check the turnaround bit: the PHY should be driving it to zero */
 169         if (mdiobb_get_bit(ctrl) != 0) {
 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");