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/*
* Bitbanged MDIO support.
*
* Author: Scott Wood <scottwood@freescale.com>
* Copyright (c) 2007 Freescale Semiconductor
*
* Based on CPM2 MDIO code which is:
*
* Copyright (c) 2003 Intracom S.A.
* by Pantelis Antoniou <panto@intracom.gr>
*
* 2005 (c) MontaVista Software, Inc.
* Vitaly Bordug <vbordug@ru.mvista.com>
*
* This file is licensed under the terms of the GNU General Public License
* version 2. This program is licensed "as is" without any warranty of any
* kind, whether express or implied.
*/
#include <linux/module.h>
#include <linux/mdio-bitbang.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/delay.h>
#define MDIO_READ 1
#define MDIO_WRITE 0
#define MDIO_SETUP_TIME 10
#define MDIO_HOLD_TIME 10
/* Minimum MDC period is 400 ns, plus some margin for error. MDIO_DELAY
* is done twice per period.
*/
#define MDIO_DELAY 250
/* The PHY may take up to 300 ns to produce data, plus some margin
* for error.
*/
#define MDIO_READ_DELAY 350
/* MDIO must already be configured as output. */
static void mdiobb_send_bit(struct mdiobb_ctrl *ctrl, int val)
{
const struct mdiobb_ops *ops = ctrl->ops;
ops->set_mdio_data(ctrl, val);
ndelay(MDIO_DELAY);
ops->set_mdc(ctrl, 1);
ndelay(MDIO_DELAY);
ops->set_mdc(ctrl, 0);
}
/* MDIO must already be configured as input. */
static int mdiobb_get_bit(struct mdiobb_ctrl *ctrl)
{
const struct mdiobb_ops *ops = ctrl->ops;
ndelay(MDIO_DELAY);
ops->set_mdc(ctrl, 1);
ndelay(MDIO_READ_DELAY);
ops->set_mdc(ctrl, 0);
return ops->get_mdio_data(ctrl);
}
/* MDIO must already be configured as output. */
static void mdiobb_send_num(struct mdiobb_ctrl *ctrl, u16 val, int bits)
{
int i;
for (i = bits - 1; i >= 0; i--)
mdiobb_send_bit(ctrl, (val >> i) & 1);
}
/* MDIO must already be configured as input. */
static u16 mdiobb_get_num(struct mdiobb_ctrl *ctrl, int bits)
{
int i;
u16 ret = 0;
for (i = bits - 1; i >= 0; i--) {
ret <<= 1;
ret |= mdiobb_get_bit(ctrl);
}
return ret;
}
/* Utility to send the preamble, address, and
* register (common to read and write).
*/
static void mdiobb_cmd(struct mdiobb_ctrl *ctrl, int read, u8 phy, u8 reg)
{
const struct mdiobb_ops *ops = ctrl->ops;
int i;
ops->set_mdio_dir(ctrl, 1);
/*
* Send a 32 bit preamble ('1's) with an extra '1' bit for good
* measure. The IEEE spec says this is a PHY optional
* requirement. The AMD 79C874 requires one after power up and
* one after a MII communications error. This means that we are
* doing more preambles than we need, but it is safer and will be
* much more robust.
*/
for (i = 0; i < 32; i++)
mdiobb_send_bit(ctrl, 1);
/* send the start bit (01) and the read opcode (10) or write (10) */
mdiobb_send_bit(ctrl, 0);
mdiobb_send_bit(ctrl, 1);
mdiobb_send_bit(ctrl, read);
mdiobb_send_bit(ctrl, !read);
mdiobb_send_num(ctrl, phy, 5);
mdiobb_send_num(ctrl, reg, 5);
}
static int mdiobb_read(struct mii_bus *bus, int phy, int reg)
{
struct mdiobb_ctrl *ctrl = bus->priv;
int ret, i;
mdiobb_cmd(ctrl, MDIO_READ, phy, reg);
ctrl->ops->set_mdio_dir(ctrl, 0);
/* check the turnaround bit: the PHY should be driving it to zero */
if (mdiobb_get_bit(ctrl) != 0) {
/* PHY didn't drive TA low -- flush any bits it
* may be trying to send.
*/
for (i = 0; i < 32; i++)
mdiobb_get_bit(ctrl);
return 0xffff;
}
ret = mdiobb_get_num(ctrl, 16);
mdiobb_get_bit(ctrl);
return ret;
}
static int mdiobb_write(struct mii_bus *bus, int phy, int reg, u16 val)
{
struct mdiobb_ctrl *ctrl = bus->priv;
mdiobb_cmd(ctrl, MDIO_WRITE, phy, reg);
/* send the turnaround (10) */
mdiobb_send_bit(ctrl, 1);
mdiobb_send_bit(ctrl, 0);
mdiobb_send_num(ctrl, val, 16);
ctrl->ops->set_mdio_dir(ctrl, 0);
mdiobb_get_bit(ctrl);
return 0;
}
struct mii_bus *alloc_mdio_bitbang(struct mdiobb_ctrl *ctrl)
{
struct mii_bus *bus;
bus = kzalloc(sizeof(struct mii_bus), GFP_KERNEL);
if (!bus)
return NULL;
__module_get(ctrl->ops->owner);
bus->read = mdiobb_read;
bus->write = mdiobb_write;
bus->priv = ctrl;
return bus;
}
void free_mdio_bitbang(struct mii_bus *bus)
{
struct mdiobb_ctrl *ctrl = bus->priv;
module_put(ctrl->ops->owner);
kfree(bus);
}
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