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
  15 #include <linux/clk.h>
  16 #include <linux/delay.h>
  17 #include <linux/io.h>
  18 #include <linux/jiffies.h>
  19 #include <linux/module.h>
  20 #include <linux/mod_devicetable.h>
  21 #include <linux/platform_device.h>
  22
  23 #include <linux/w1.h>
  24
  25 /*
  26  * MXC W1 Register offsets
  27  */
  28 #define MXC_W1_CONTROL          0x00
  29 # define MXC_W1_CONTROL_RDST    BIT(3)
  30 # define MXC_W1_CONTROL_WR(x)   BIT(5 - (x))
  31 # define MXC_W1_CONTROL_PST     BIT(6)
  32 # define MXC_W1_CONTROL_RPP     BIT(7)
  33 #define MXC_W1_TIME_DIVIDER     0x02
  34 #define MXC_W1_RESET            0x04
  35 # define MXC_W1_RESET_RST       BIT(0)
  36
  37 struct mxc_w1_device {
  38         void __iomem *regs;
  39         struct clk *clk;
  40         struct w1_bus_master bus_master;
  41 };
  42
  43 /*
  44  * this is the low level routine to
  45  * reset the device on the One Wire interface
  46  * on the hardware
  47  */
  48 static u8 mxc_w1_ds2_reset_bus(void *data)
  49 {
  50         struct mxc_w1_device *dev = data;
  51         unsigned long timeout;
  52
  53         writeb(MXC_W1_CONTROL_RPP, dev->regs + MXC_W1_CONTROL);
  54
  55         /* Wait for reset sequence 511+512us, use 1500us for sure */
  56         timeout = jiffies + usecs_to_jiffies(1500);
  57
  58         udelay(511 + 512);
  59
  60         do {
  61                 u8 ctrl = readb(dev->regs + MXC_W1_CONTROL);
  62
  63                 /* PST bit is valid after the RPP bit is self-cleared */
  64                 if (!(ctrl & MXC_W1_CONTROL_RPP))
  65                         return !(ctrl & MXC_W1_CONTROL_PST);
  66         } while (time_is_after_jiffies(timeout));
  67
  68         return 1;
  69 }
  70
  71 /*
  72  * this is the low level routine to read/write a bit on the One Wire
  73  * interface on the hardware. It does write 0 if parameter bit is set
  74  * to 0, otherwise a write 1/read.
  75  */
  76 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
  77 {
  78         struct mxc_w1_device *dev = data;
  79         unsigned long timeout;
  80
  81         writeb(MXC_W1_CONTROL_WR(bit), dev->regs + MXC_W1_CONTROL);
  82
  83         /* Wait for read/write bit (60us, Max 120us), use 200us for sure */
  84         timeout = jiffies + usecs_to_jiffies(200);
  85
  86         udelay(60);
  87
  88         do {
  89                 u8 ctrl = readb(dev->regs + MXC_W1_CONTROL);
  90
  91                 /* RDST bit is valid after the WR1/RD bit is self-cleared */
  92                 if (!(ctrl & MXC_W1_CONTROL_WR(bit)))
  93                         return !!(ctrl & MXC_W1_CONTROL_RDST);
  94         } while (time_is_after_jiffies(timeout));
  95
  96         return 0;
  97 }
  98
  99 static int mxc_w1_probe(struct platform_device *pdev)
 100 {
 101         struct mxc_w1_device *mdev;
 102         unsigned long clkrate;
 103         struct resource *res;
 104         unsigned int clkdiv;
 105         int err;
 106
 107         mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
 108                             GFP_KERNEL);
 109         if (!mdev)
 110                 return -ENOMEM;
 111
 112         mdev->clk = devm_clk_get(&pdev->dev, NULL);
 113         if (IS_ERR(mdev->clk))
 114                 return PTR_ERR(mdev->clk);
 115
 116         err = clk_prepare_enable(mdev->clk);
 117         if (err)
 118                 return err;
 119
 120         clkrate = clk_get_rate(mdev->clk);
 121         if (clkrate < 10000000)
 122                 dev_warn(&pdev->dev,
 123                          "Low clock frequency causes improper function\n");
 124
 125         clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
 126         clkrate /= clkdiv;
 127         if ((clkrate < 980000) || (clkrate > 1020000))
 128                 dev_warn(&pdev->dev,
 129                          "Incorrect time base frequency %lu Hz\n", clkrate);
 130
 131         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 132         mdev->regs = devm_ioremap_resource(&pdev->dev, res);
 133         if (IS_ERR(mdev->regs)) {
 134                 err = PTR_ERR(mdev->regs);
 135                 goto out_disable_clk;
 136         }
 137
 138         /* Software reset 1-Wire module */
 139         writeb(MXC_W1_RESET_RST, mdev->regs + MXC_W1_RESET);
 140         writeb(0, mdev->regs + MXC_W1_RESET);
 141
 142         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                 goto out_disable_clk;
 153
 154         return 0;
 155
 156 out_disable_clk:
 157         clk_disable_unprepare(mdev->clk);
 158         return err;
 159 }
 160
 161 /*
 162  * disassociate the w1 device from the driver
 163  */
 164 static int mxc_w1_remove(struct platform_device *pdev)
 165 {
 166         struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
 167
 168         w1_remove_master_device(&mdev->bus_master);
 169
 170         clk_disable_unprepare(mdev->clk);
 171
 172         return 0;
 173 }
 174
 175 static const struct of_device_id mxc_w1_dt_ids[] = {
 176         { .compatible = "fsl,imx21-owire" },
 177         { /* sentinel */ }
 178 };
 179 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
 180
 181 static struct platform_driver mxc_w1_driver = {
 182         .driver = {
 183                 .name = "mxc_w1",
 184                 .of_match_table = mxc_w1_dt_ids,
 185         },
 186         .probe = mxc_w1_probe,
 187         .remove = mxc_w1_remove,
 188 };
 189 module_platform_driver(mxc_w1_driver);
 190
 191 MODULE_LICENSE("GPL");
 192 MODULE_AUTHOR("Freescale Semiconductors Inc");
 193 MODULE_DESCRIPTION("Driver for One-Wire on MXC");