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/slab.h>
  23 #include <linux/types.h>
  24 #include <linux/delay.h>
  25
  26 #define MDIO_READ 1
  27 #define MDIO_WRITE 0
  28
  29 #define MDIO_SETUP_TIME 10
  30 #define MDIO_HOLD_TIME 10
  31
  32 /* Minimum MDC period is 400 ns, plus some margin for error.  MDIO_DELAY
  33  * is done twice per period.
  34  */
  35 #define MDIO_DELAY 250
  36
  37 /* The PHY may take up to 300 ns to produce data, plus some margin
  38  * for error.
  39  */
  40 #define MDIO_READ_DELAY 350
  41
  42 /* MDIO must already be configured as output. */
  43 static void mdiobb_send_bit(struct mdiobb_ctrl *ctrl, int val)
  44 {
  45         const struct mdiobb_ops *ops = ctrl->ops;
  46
  47         ops->set_mdio_data(ctrl, val);
  48         ndelay(MDIO_DELAY);
  49         ops->set_mdc(ctrl, 1);
  50         ndelay(MDIO_DELAY);
  51         ops->set_mdc(ctrl, 0);
  52 }
  53
  54 /* MDIO must already be configured as input. */
  55 static int mdiobb_get_bit(struct mdiobb_ctrl *ctrl)
  56 {
  57         const struct mdiobb_ops *ops = ctrl->ops;
  58
  59         ndelay(MDIO_DELAY);
  60         ops->set_mdc(ctrl, 1);
  61         ndelay(MDIO_READ_DELAY);
  62         ops->set_mdc(ctrl, 0);
  63
  64         return ops->get_mdio_data(ctrl);
  65 }
  66
  67 /* MDIO must already be configured as output. */
  68 static void mdiobb_send_num(struct mdiobb_ctrl *ctrl, u16 val, int bits)
  69 {
  70         int i;
  71
  72         for (i = bits - 1; i >= 0; i--)
  73                 mdiobb_send_bit(ctrl, (val >> i) & 1);
  74 }
  75
  76 /* MDIO must already be configured as input. */
  77 static u16 mdiobb_get_num(struct mdiobb_ctrl *ctrl, int bits)
  78 {
  79         int i;
  80         u16 ret = 0;
  81
  82         for (i = bits - 1; i >= 0; i--) {
  83                 ret <<= 1;
  84                 ret |= mdiobb_get_bit(ctrl);
  85         }
  86
  87         return ret;
  88 }
  89
  90 /* Utility to send the preamble, address, and
  91  * register (common to read and write).
  92  */
  93 static void mdiobb_cmd(struct mdiobb_ctrl *ctrl, int read, u8 phy, u8 reg)
  94 {
  95         const struct mdiobb_ops *ops = ctrl->ops;
  96         int i;
  97
  98         ops->set_mdio_dir(ctrl, 1);
  99
 100         /*
 101          * Send a 32 bit preamble ('1's) with an extra '1' bit for good
 102          * measure.  The IEEE spec says this is a PHY optional
 103          * requirement.  The AMD 79C874 requires one after power up and
 104          * one after a MII communications error.  This means that we are
 105          * doing more preambles than we need, but it is safer and will be
 106          * much more robust.
 107          */
 108
 109         for (i = 0; i < 32; i++)
 110                 mdiobb_send_bit(ctrl, 1);
 111
 112         /* send the start bit (01) and the read opcode (10) or write (10) */
 113         mdiobb_send_bit(ctrl, 0);
 114         mdiobb_send_bit(ctrl, 1);
 115         mdiobb_send_bit(ctrl, read);
 116         mdiobb_send_bit(ctrl, !read);
 117
 118         mdiobb_send_num(ctrl, phy, 5);
 119         mdiobb_send_num(ctrl, reg, 5);
 120 }
 121
 122
 123 static int mdiobb_read(struct mii_bus *bus, int phy, int reg)
 124 {
 125         struct mdiobb_ctrl *ctrl = bus->priv;
 126         int ret, i;
 127
 128         mdiobb_cmd(ctrl, MDIO_READ, phy, reg);
 129         ctrl->ops->set_mdio_dir(ctrl, 0);
 130
 131         /* check the turnaround bit: the PHY should be driving it to zero */
 132         if (mdiobb_get_bit(ctrl) != 0) {
 133                 /* PHY didn't drive TA low -- flush any bits it
 134                  * may be trying to send.
 135                  */
 136                 for (i = 0; i < 32; i++)
 137                         mdiobb_get_bit(ctrl);
 138
 139                 return 0xffff;
 140         }
 141
 142         ret = mdiobb_get_num(ctrl, 16);
 143         mdiobb_get_bit(ctrl);
 144         return ret;
 145 }
 146
 147 static int mdiobb_write(struct mii_bus *bus, int phy, int reg, u16 val)
 148 {
 149         struct mdiobb_ctrl *ctrl = bus->priv;
 150
 151         mdiobb_cmd(ctrl, MDIO_WRITE, phy, reg);
 152
 153         /* send the turnaround (10) */
 154         mdiobb_send_bit(ctrl, 1);
 155         mdiobb_send_bit(ctrl, 0);
 156
 157         mdiobb_send_num(ctrl, val, 16);
 158
 159         ctrl->ops->set_mdio_dir(ctrl, 0);
 160         mdiobb_get_bit(ctrl);
 161         return 0;
 162 }
 163
 164 struct mii_bus *alloc_mdio_bitbang(struct mdiobb_ctrl *ctrl)
 165 {
 166         struct mii_bus *bus;
 167
 168         bus = mdiobus_alloc();
 169         if (!bus)
 170                 return NULL;
 171
 172         __module_get(ctrl->ops->owner);
 173
 174         bus->read = mdiobb_read;
 175         bus->write = mdiobb_write;
 176         bus->priv = ctrl;
 177
 178         return bus;
 179 }
 180 EXPORT_SYMBOL(alloc_mdio_bitbang);
 181
 182 void free_mdio_bitbang(struct mii_bus *bus)
 183 {
 184         struct mdiobb_ctrl *ctrl = bus->priv;
 185
 186         module_put(ctrl->ops->owner);
 187         mdiobus_free(bus);
 188 }
 189 EXPORT_SYMBOL(free_mdio_bitbang);
 190
 191 MODULE_LICENSE("GPL");