drivers/watchdog/pic32-dmt.c

   1 /*
   2  * PIC32 deadman timer driver
   3  *
   4  * Purna Chandra Mandal <purna.mandal@microchip.com>
   5  * Copyright (c) 2016, Microchip Technology Inc.
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  */
  12 #include <linux/clk.h>
  13 #include <linux/device.h>
  14 #include <linux/err.h>
  15 #include <linux/io.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/of.h>
  19 #include <linux/of_device.h>
  20 #include <linux/platform_device.h>
  21 #include <linux/pm.h>
  22 #include <linux/watchdog.h>
  23
  24 #include <asm/mach-pic32/pic32.h>
  25
  26 /* Deadman Timer Regs */
  27 #define DMTCON_REG      0x00
  28 #define DMTPRECLR_REG   0x10
  29 #define DMTCLR_REG      0x20
  30 #define DMTSTAT_REG     0x30
  31 #define DMTCNT_REG      0x40
  32 #define DMTPSCNT_REG    0x60
  33 #define DMTPSINTV_REG   0x70
  34
  35 /* Deadman Timer Regs fields */
  36 #define DMT_ON                  BIT(15)
  37 #define DMT_STEP1_KEY           BIT(6)
  38 #define DMT_STEP2_KEY           BIT(3)
  39 #define DMTSTAT_WINOPN          BIT(0)
  40 #define DMTSTAT_EVENT           BIT(5)
  41 #define DMTSTAT_BAD2            BIT(6)
  42 #define DMTSTAT_BAD1            BIT(7)
  43
  44 /* Reset Control Register fields for watchdog */
  45 #define RESETCON_DMT_TIMEOUT    BIT(5)
  46
  47 struct pic32_dmt {
  48         void __iomem    *regs;
  49         struct clk      *clk;
  50 };
  51
  52 static inline void dmt_enable(struct pic32_dmt *dmt)
  53 {
  54         writel(DMT_ON, PIC32_SET(dmt->regs + DMTCON_REG));
  55 }
  56
  57 static inline void dmt_disable(struct pic32_dmt *dmt)
  58 {
  59         writel(DMT_ON, PIC32_CLR(dmt->regs + DMTCON_REG));
  60         /*
  61          * Cannot touch registers in the CPU cycle following clearing the
  62          * ON bit.
  63          */
  64         nop();
  65 }
  66
  67 static inline int dmt_bad_status(struct pic32_dmt *dmt)
  68 {
  69         u32 val;
  70
  71         val = readl(dmt->regs + DMTSTAT_REG);
  72         val &= (DMTSTAT_BAD1 | DMTSTAT_BAD2 | DMTSTAT_EVENT);
  73         if (val)
  74                 return -EAGAIN;
  75
  76         return 0;
  77 }
  78
  79 static inline int dmt_keepalive(struct pic32_dmt *dmt)
  80 {
  81         u32 v;
  82         u32 timeout = 500;
  83
  84         /* set pre-clear key */
  85         writel(DMT_STEP1_KEY << 8, dmt->regs + DMTPRECLR_REG);
  86
  87         /* wait for DMT window to open */
  88         while (--timeout) {
  89                 v = readl(dmt->regs + DMTSTAT_REG) & DMTSTAT_WINOPN;
  90                 if (v == DMTSTAT_WINOPN)
  91                         break;
  92         }
  93
  94         /* apply key2 */
  95         writel(DMT_STEP2_KEY, dmt->regs + DMTCLR_REG);
  96
  97         /* check whether keys are latched correctly */
  98         return dmt_bad_status(dmt);
  99 }
 100
 101 static inline u32 pic32_dmt_get_timeout_secs(struct pic32_dmt *dmt)
 102 {
 103         unsigned long rate;
 104
 105         rate = clk_get_rate(dmt->clk);
 106         if (rate)
 107                 return readl(dmt->regs + DMTPSCNT_REG) / rate;
 108
 109         return 0;
 110 }
 111
 112 static inline u32 pic32_dmt_bootstatus(struct pic32_dmt *dmt)
 113 {
 114         u32 v;
 115         void __iomem *rst_base;
 116
 117         rst_base = ioremap(PIC32_BASE_RESET, 0x10);
 118         if (!rst_base)
 119                 return 0;
 120
 121         v = readl(rst_base);
 122
 123         writel(RESETCON_DMT_TIMEOUT, PIC32_CLR(rst_base));
 124
 125         iounmap(rst_base);
 126         return v & RESETCON_DMT_TIMEOUT;
 127 }
 128
 129 static int pic32_dmt_start(struct watchdog_device *wdd)
 130 {
 131         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 132
 133         dmt_enable(dmt);
 134         return dmt_keepalive(dmt);
 135 }
 136
 137 static int pic32_dmt_stop(struct watchdog_device *wdd)
 138 {
 139         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 140
 141         dmt_disable(dmt);
 142
 143         return 0;
 144 }
 145
 146 static int pic32_dmt_ping(struct watchdog_device *wdd)
 147 {
 148         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 149
 150         return dmt_keepalive(dmt);
 151 }
 152
 153 static const struct watchdog_ops pic32_dmt_fops = {
 154         .owner          = THIS_MODULE,
 155         .start          = pic32_dmt_start,
 156         .stop           = pic32_dmt_stop,
 157         .ping           = pic32_dmt_ping,
 158 };
 159
 160 static const struct watchdog_info pic32_dmt_ident = {
 161         .options        = WDIOF_KEEPALIVEPING |
 162                           WDIOF_MAGICCLOSE,
 163         .identity       = "PIC32 Deadman Timer",
 164 };
 165
 166 static struct watchdog_device pic32_dmt_wdd = {
 167         .info           = &pic32_dmt_ident,
 168         .ops            = &pic32_dmt_fops,
 169 };
 170
 171 static int pic32_dmt_probe(struct platform_device *pdev)
 172 {
 173         int ret;
 174         struct pic32_dmt *dmt;
 175         struct resource *mem;
 176         struct watchdog_device *wdd = &pic32_dmt_wdd;
 177
 178         dmt = devm_kzalloc(&pdev->dev, sizeof(*dmt), GFP_KERNEL);
 179         if (!dmt)
 180                 return -ENOMEM;
 181
 182         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 183         dmt->regs = devm_ioremap_resource(&pdev->dev, mem);
 184         if (IS_ERR(dmt->regs))
 185                 return PTR_ERR(dmt->regs);
 186
 187         dmt->clk = devm_clk_get(&pdev->dev, NULL);
 188         if (IS_ERR(dmt->clk)) {
 189                 dev_err(&pdev->dev, "clk not found\n");
 190                 return PTR_ERR(dmt->clk);
 191         }
 192
 193         ret = clk_prepare_enable(dmt->clk);
 194         if (ret)
 195                 return ret;
 196
 197         wdd->timeout = pic32_dmt_get_timeout_secs(dmt);
 198         if (!wdd->timeout) {
 199                 dev_err(&pdev->dev,
 200                         "failed to read watchdog register timeout\n");
 201                 ret = -EINVAL;
 202                 goto out_disable_clk;
 203         }
 204
 205         dev_info(&pdev->dev, "timeout %d\n", wdd->timeout);
 206
 207         wdd->bootstatus = pic32_dmt_bootstatus(dmt) ? WDIOF_CARDRESET : 0;
 208
 209         watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
 210         watchdog_set_drvdata(wdd, dmt);
 211
 212         ret = watchdog_register_device(wdd);
 213         if (ret) {
 214                 dev_err(&pdev->dev, "watchdog register failed, err %d\n", ret);
 215                 goto out_disable_clk;
 216         }
 217
 218         platform_set_drvdata(pdev, wdd);
 219         return 0;
 220
 221 out_disable_clk:
 222         clk_disable_unprepare(dmt->clk);
 223         return ret;
 224 }
 225
 226 static int pic32_dmt_remove(struct platform_device *pdev)
 227 {
 228         struct watchdog_device *wdd = platform_get_drvdata(pdev);
 229         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 230
 231         watchdog_unregister_device(wdd);
 232         clk_disable_unprepare(dmt->clk);
 233
 234         return 0;
 235 }
 236
 237 static const struct of_device_id pic32_dmt_of_ids[] = {
 238         { .compatible = "microchip,pic32mzda-dmt",},
 239         { /* sentinel */ }
 240 };
 241 MODULE_DEVICE_TABLE(of, pic32_dmt_of_ids);
 242
 243 static struct platform_driver pic32_dmt_driver = {
 244         .probe          = pic32_dmt_probe,
 245         .remove         = pic32_dmt_remove,
 246         .driver         = {
 247                 .name           = "pic32-dmt",
 248                 .of_match_table = of_match_ptr(pic32_dmt_of_ids),
 249         }
 250 };
 251
 252 module_platform_driver(pic32_dmt_driver);
 253
 254 MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@microchip.com>");
 255 MODULE_DESCRIPTION("Microchip PIC32 DMT Driver");
 256 MODULE_LICENSE("GPL");