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         struct clk *clk;
  50         struct w1_bus_master bus_master;
  51 };
  52
  53 /*
  54  * this is the low level routine to
  55  * reset the device on the One Wire interface
  56  * on the hardware
  57  */
  58 static u8 mxc_w1_ds2_reset_bus(void *data)
  59 {
  60         u8 reg_val;
  61         unsigned int timeout_cnt = 0;
  62         struct mxc_w1_device *dev = data;
  63
  64         __raw_writeb(0x80, (dev->regs + MXC_W1_CONTROL));
  65
  66         while (1) {
  67                 reg_val = __raw_readb(dev->regs + MXC_W1_CONTROL);
  68
  69                 if (((reg_val >> 7) & 0x1) == 0 ||
  70                     timeout_cnt > MXC_W1_RESET_TIMEOUT)
  71                         break;
  72                 else
  73                         timeout_cnt++;
  74
  75                 udelay(100);
  76         }
  77         return (reg_val >> 7) & 0x1;
  78 }
  79
  80 /*
  81  * this is the low level routine to read/write a bit on the One Wire
  82  * interface on the hardware. It does write 0 if parameter bit is set
  83  * to 0, otherwise a write 1/read.
  84  */
  85 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
  86 {
  87         struct mxc_w1_device *mdev = data;
  88         void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL;
  89         unsigned int timeout_cnt = 400; /* Takes max. 120us according to
  90                                          * datasheet.
  91                                          */
  92
  93         __raw_writeb((1 << (5 - bit)), ctrl_addr);
  94
  95         while (timeout_cnt--) {
  96                 if (!((__raw_readb(ctrl_addr) >> (5 - bit)) & 0x1))
  97                         break;
  98
  99                 udelay(1);
 100         }
 101
 102         return ((__raw_readb(ctrl_addr)) >> 3) & 0x1;
 103 }
 104
 105 static int mxc_w1_probe(struct platform_device *pdev)
 106 {
 107         struct mxc_w1_device *mdev;
 108         unsigned long clkrate;
 109         struct resource *res;
 110         unsigned int clkdiv;
 111         int err;
 112
 113         mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
 114                             GFP_KERNEL);
 115         if (!mdev)
 116                 return -ENOMEM;
 117
 118         mdev->clk = devm_clk_get(&pdev->dev, NULL);
 119         if (IS_ERR(mdev->clk))
 120                 return PTR_ERR(mdev->clk);
 121
 122         clkrate = clk_get_rate(mdev->clk);
 123         if (clkrate < 10000000)
 124                 dev_warn(&pdev->dev,
 125                          "Low clock frequency causes improper function\n");
 126
 127         clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
 128         clkrate /= clkdiv;
 129         if ((clkrate < 980000) || (clkrate > 1020000))
 130                 dev_warn(&pdev->dev,
 131                          "Incorrect time base frequency %lu Hz\n", clkrate);
 132
 133         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 134         mdev->regs = devm_ioremap_resource(&pdev->dev, res);
 135         if (IS_ERR(mdev->regs))
 136                 return PTR_ERR(mdev->regs);
 137
 138         err = clk_prepare_enable(mdev->clk);
 139         if (err)
 140                 return err;
 141
 142         __raw_writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
 143
 144         mdev->bus_master.data = mdev;
 145         mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
 146         mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
 147
 148         platform_set_drvdata(pdev, mdev);
 149
 150         err = w1_add_master_device(&mdev->bus_master);
 151         if (err)
 152                 clk_disable_unprepare(mdev->clk);
 153
 154         return err;
 155 }
 156
 157 /*
 158  * disassociate the w1 device from the driver
 159  */
 160 static int mxc_w1_remove(struct platform_device *pdev)
 161 {
 162         struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
 163
 164         w1_remove_master_device(&mdev->bus_master);
 165
 166         clk_disable_unprepare(mdev->clk);
 167
 168         return 0;
 169 }
 170
 171 static struct of_device_id mxc_w1_dt_ids[] = {
 172         { .compatible = "fsl,imx21-owire" },
 173         { /* sentinel */ }
 174 };
 175 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
 176
 177 static struct platform_driver mxc_w1_driver = {
 178         .driver = {
 179                 .name = "mxc_w1",
 180                 .of_match_table = mxc_w1_dt_ids,
 181         },
 182         .probe = mxc_w1_probe,
 183         .remove = mxc_w1_remove,
 184 };
 185 module_platform_driver(mxc_w1_driver);
 186
 187 MODULE_LICENSE("GPL");
 188 MODULE_AUTHOR("Freescale Semiconductors Inc");
 189 MODULE_DESCRIPTION("Driver for One-Wire on MXC");