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/*
* Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved.
* Copyright 2008 Luotao Fu, kernel@pengutronix.de
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include "../w1.h"
#include "../w1_int.h"
/* According to the mx27 Datasheet the reset procedure should take up to about
* 1350us. We set the timeout to 500*100us = 50ms for sure */
#define MXC_W1_RESET_TIMEOUT 500
/*
* MXC W1 Register offsets
*/
#define MXC_W1_CONTROL 0x00
# define MXC_W1_CONTROL_RDST BIT(3)
# define MXC_W1_CONTROL_WR(x) BIT(5 - (x))
# define MXC_W1_CONTROL_PST BIT(6)
# define MXC_W1_CONTROL_RPP BIT(7)
#define MXC_W1_TIME_DIVIDER 0x02
#define MXC_W1_RESET 0x04
struct mxc_w1_device {
void __iomem *regs;
struct clk *clk;
struct w1_bus_master bus_master;
};
/*
* this is the low level routine to
* reset the device on the One Wire interface
* on the hardware
*/
static u8 mxc_w1_ds2_reset_bus(void *data)
{
u8 reg_val;
unsigned int timeout_cnt = 0;
struct mxc_w1_device *dev = data;
writeb(MXC_W1_CONTROL_RPP, (dev->regs + MXC_W1_CONTROL));
while (1) {
reg_val = readb(dev->regs + MXC_W1_CONTROL);
if (!(reg_val & MXC_W1_CONTROL_RPP) ||
timeout_cnt > MXC_W1_RESET_TIMEOUT)
break;
else
timeout_cnt++;
udelay(100);
}
return !(reg_val & MXC_W1_CONTROL_PST);
}
/*
* this is the low level routine to read/write a bit on the One Wire
* interface on the hardware. It does write 0 if parameter bit is set
* to 0, otherwise a write 1/read.
*/
static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
{
struct mxc_w1_device *mdev = data;
void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL;
unsigned int timeout_cnt = 400; /* Takes max. 120us according to
* datasheet.
*/
writeb(MXC_W1_CONTROL_WR(bit), ctrl_addr);
while (timeout_cnt--) {
if (!(readb(ctrl_addr) & MXC_W1_CONTROL_WR(bit)))
break;
udelay(1);
}
return !!(readb(ctrl_addr) & MXC_W1_CONTROL_RDST);
}
static int mxc_w1_probe(struct platform_device *pdev)
{
struct mxc_w1_device *mdev;
unsigned long clkrate;
struct resource *res;
unsigned int clkdiv;
int err;
mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
GFP_KERNEL);
if (!mdev)
return -ENOMEM;
mdev->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(mdev->clk))
return PTR_ERR(mdev->clk);
clkrate = clk_get_rate(mdev->clk);
if (clkrate < 10000000)
dev_warn(&pdev->dev,
"Low clock frequency causes improper function\n");
clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
clkrate /= clkdiv;
if ((clkrate < 980000) || (clkrate > 1020000))
dev_warn(&pdev->dev,
"Incorrect time base frequency %lu Hz\n", clkrate);
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
mdev->regs = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(mdev->regs))
return PTR_ERR(mdev->regs);
err = clk_prepare_enable(mdev->clk);
if (err)
return err;
writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
mdev->bus_master.data = mdev;
mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
platform_set_drvdata(pdev, mdev);
err = w1_add_master_device(&mdev->bus_master);
if (err)
clk_disable_unprepare(mdev->clk);
return err;
}
/*
* disassociate the w1 device from the driver
*/
static int mxc_w1_remove(struct platform_device *pdev)
{
struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
w1_remove_master_device(&mdev->bus_master);
clk_disable_unprepare(mdev->clk);
return 0;
}
static struct of_device_id mxc_w1_dt_ids[] = {
{ .compatible = "fsl,imx21-owire" },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
static struct platform_driver mxc_w1_driver = {
.driver = {
.name = "mxc_w1",
.owner = THIS_MODULE,
.of_match_table = mxc_w1_dt_ids,
},
.probe = mxc_w1_probe,
.remove = mxc_w1_remove,
};
module_platform_driver(mxc_w1_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Freescale Semiconductors Inc");
MODULE_DESCRIPTION("Driver for One-Wire on MXC");
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