drivers/w1/masters/mxc_w1.c

   1 /*
   2  * Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved.
   3  * Copyright 2008 Luotao Fu, kernel@pengutronix.de
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  17  *
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/clk.h>
  24 #include <linux/slab.h>
  25 #include <linux/delay.h>
  26 #include <linux/io.h>
  27
  28 #include "../w1.h"
  29 #include "../w1_int.h"
  30 #include "../w1_log.h"
  31
  32 /* According to the mx27 Datasheet the reset procedure should take up to about
  33  * 1350us. We set the timeout to 500*100us = 50ms for sure */
  34 #define MXC_W1_RESET_TIMEOUT 500
  35
  36 /*
  37  * MXC W1 Register offsets
  38  */
  39 #define MXC_W1_CONTROL          0x00
  40 #define MXC_W1_TIME_DIVIDER     0x02
  41 #define MXC_W1_RESET            0x04
  42 #define MXC_W1_COMMAND          0x06
  43 #define MXC_W1_TXRX             0x08
  44 #define MXC_W1_INTERRUPT        0x0A
  45 #define MXC_W1_INTERRUPT_EN     0x0C
  46
  47 struct mxc_w1_device {
  48         void __iomem *regs;
  49         unsigned int clkdiv;
  50         struct clk *clk;
  51         struct w1_bus_master bus_master;
  52 };
  53
  54 /*
  55  * this is the low level routine to
  56  * reset the device on the One Wire interface
  57  * on the hardware
  58  */
  59 static u8 mxc_w1_ds2_reset_bus(void *data)
  60 {
  61         u8 reg_val;
  62         unsigned int timeout_cnt = 0;
  63         struct mxc_w1_device *dev = data;
  64
  65         __raw_writeb(0x80, (dev->regs + MXC_W1_CONTROL));
  66
  67         while (1) {
  68                 reg_val = __raw_readb(dev->regs + MXC_W1_CONTROL);
  69
  70                 if (((reg_val >> 7) & 0x1) == 0 ||
  71                     timeout_cnt > MXC_W1_RESET_TIMEOUT)
  72                         break;
  73                 else
  74                         timeout_cnt++;
  75
  76                 udelay(100);
  77         }
  78         return (reg_val >> 7) & 0x1;
  79 }
  80
  81 /*
  82  * this is the low level routine to read/write a bit on the One Wire
  83  * interface on the hardware. It does write 0 if parameter bit is set
  84  * to 0, otherwise a write 1/read.
  85  */
  86 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
  87 {
  88         struct mxc_w1_device *mdev = data;
  89         void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL;
  90         unsigned int timeout_cnt = 400; /* Takes max. 120us according to
  91                                          * datasheet.
  92                                          */
  93
  94         __raw_writeb((1 << (5 - bit)), ctrl_addr);
  95
  96         while (timeout_cnt--) {
  97                 if (!((__raw_readb(ctrl_addr) >> (5 - bit)) & 0x1))
  98                         break;
  99
 100                 udelay(1);
 101         }
 102
 103         return ((__raw_readb(ctrl_addr)) >> 3) & 0x1;
 104 }
 105
 106 static int mxc_w1_probe(struct platform_device *pdev)
 107 {
 108         struct mxc_w1_device *mdev;
 109         struct resource *res;
 110         int err = 0;
 111
 112         mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
 113                             GFP_KERNEL);
 114         if (!mdev)
 115                 return -ENOMEM;
 116
 117         mdev->clk = devm_clk_get(&pdev->dev, NULL);
 118         if (IS_ERR(mdev->clk))
 119                 return PTR_ERR(mdev->clk);
 120
 121         mdev->clkdiv = (clk_get_rate(mdev->clk) / 1000000) - 1;
 122
 123         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 124         mdev->regs = devm_ioremap_resource(&pdev->dev, res);
 125         if (IS_ERR(mdev->regs))
 126                 return PTR_ERR(mdev->regs);
 127
 128         clk_prepare_enable(mdev->clk);
 129         __raw_writeb(mdev->clkdiv, mdev->regs + MXC_W1_TIME_DIVIDER);
 130
 131         mdev->bus_master.data = mdev;
 132         mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
 133         mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
 134
 135         err = w1_add_master_device(&mdev->bus_master);
 136
 137         if (err)
 138                 return err;
 139
 140         platform_set_drvdata(pdev, mdev);
 141         return 0;
 142 }
 143
 144 /*
 145  * disassociate the w1 device from the driver
 146  */
 147 static int mxc_w1_remove(struct platform_device *pdev)
 148 {
 149         struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
 150
 151         w1_remove_master_device(&mdev->bus_master);
 152
 153         clk_disable_unprepare(mdev->clk);
 154
 155         platform_set_drvdata(pdev, NULL);
 156
 157         return 0;
 158 }
 159
 160 static struct of_device_id mxc_w1_dt_ids[] = {
 161         { .compatible = "fsl,imx21-owire" },
 162         { /* sentinel */ }
 163 };
 164 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
 165
 166 static struct platform_driver mxc_w1_driver = {
 167         .driver = {
 168                 .name = "mxc_w1",
 169                 .of_match_table = mxc_w1_dt_ids,
 170         },
 171         .probe = mxc_w1_probe,
 172         .remove = mxc_w1_remove,
 173 };
 174 module_platform_driver(mxc_w1_driver);
 175
 176 MODULE_LICENSE("GPL");
 177 MODULE_AUTHOR("Freescale Semiconductors Inc");
 178 MODULE_DESCRIPTION("Driver for One-Wire on MXC");