drivers/watchdog/pic32-dmt.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * PIC32 deadman timer driver
   4  *
   5  * Purna Chandra Mandal <purna.mandal@microchip.com>
   6  * Copyright (c) 2016, Microchip Technology Inc.
   7  */
   8 #include <linux/clk.h>
   9 #include <linux/device.h>
  10 #include <linux/err.h>
  11 #include <linux/io.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/of.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/pm.h>
  17 #include <linux/watchdog.h>
  18
  19 #include <asm/mach-pic32/pic32.h>
  20
  21 /* Deadman Timer Regs */
  22 #define DMTCON_REG      0x00
  23 #define DMTPRECLR_REG   0x10
  24 #define DMTCLR_REG      0x20
  25 #define DMTSTAT_REG     0x30
  26 #define DMTCNT_REG      0x40
  27 #define DMTPSCNT_REG    0x60
  28 #define DMTPSINTV_REG   0x70
  29
  30 /* Deadman Timer Regs fields */
  31 #define DMT_ON                  BIT(15)
  32 #define DMT_STEP1_KEY           BIT(6)
  33 #define DMT_STEP2_KEY           BIT(3)
  34 #define DMTSTAT_WINOPN          BIT(0)
  35 #define DMTSTAT_EVENT           BIT(5)
  36 #define DMTSTAT_BAD2            BIT(6)
  37 #define DMTSTAT_BAD1            BIT(7)
  38
  39 /* Reset Control Register fields for watchdog */
  40 #define RESETCON_DMT_TIMEOUT    BIT(5)
  41
  42 struct pic32_dmt {
  43         void __iomem    *regs;
  44         struct clk      *clk;
  45 };
  46
  47 static inline void dmt_enable(struct pic32_dmt *dmt)
  48 {
  49         writel(DMT_ON, PIC32_SET(dmt->regs + DMTCON_REG));
  50 }
  51
  52 static inline void dmt_disable(struct pic32_dmt *dmt)
  53 {
  54         writel(DMT_ON, PIC32_CLR(dmt->regs + DMTCON_REG));
  55         /*
  56          * Cannot touch registers in the CPU cycle following clearing the
  57          * ON bit.
  58          */
  59         nop();
  60 }
  61
  62 static inline int dmt_bad_status(struct pic32_dmt *dmt)
  63 {
  64         u32 val;
  65
  66         val = readl(dmt->regs + DMTSTAT_REG);
  67         val &= (DMTSTAT_BAD1 | DMTSTAT_BAD2 | DMTSTAT_EVENT);
  68         if (val)
  69                 return -EAGAIN;
  70
  71         return 0;
  72 }
  73
  74 static inline int dmt_keepalive(struct pic32_dmt *dmt)
  75 {
  76         u32 v;
  77         u32 timeout = 500;
  78
  79         /* set pre-clear key */
  80         writel(DMT_STEP1_KEY << 8, dmt->regs + DMTPRECLR_REG);
  81
  82         /* wait for DMT window to open */
  83         while (--timeout) {
  84                 v = readl(dmt->regs + DMTSTAT_REG) & DMTSTAT_WINOPN;
  85                 if (v == DMTSTAT_WINOPN)
  86                         break;
  87         }
  88
  89         /* apply key2 */
  90         writel(DMT_STEP2_KEY, dmt->regs + DMTCLR_REG);
  91
  92         /* check whether keys are latched correctly */
  93         return dmt_bad_status(dmt);
  94 }
  95
  96 static inline u32 pic32_dmt_get_timeout_secs(struct pic32_dmt *dmt)
  97 {
  98         unsigned long rate;
  99
 100         rate = clk_get_rate(dmt->clk);
 101         if (rate)
 102                 return readl(dmt->regs + DMTPSCNT_REG) / rate;
 103
 104         return 0;
 105 }
 106
 107 static inline u32 pic32_dmt_bootstatus(struct pic32_dmt *dmt)
 108 {
 109         u32 v;
 110         void __iomem *rst_base;
 111
 112         rst_base = ioremap(PIC32_BASE_RESET, 0x10);
 113         if (!rst_base)
 114                 return 0;
 115
 116         v = readl(rst_base);
 117
 118         writel(RESETCON_DMT_TIMEOUT, PIC32_CLR(rst_base));
 119
 120         iounmap(rst_base);
 121         return v & RESETCON_DMT_TIMEOUT;
 122 }
 123
 124 static int pic32_dmt_start(struct watchdog_device *wdd)
 125 {
 126         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 127
 128         dmt_enable(dmt);
 129         return dmt_keepalive(dmt);
 130 }
 131
 132 static int pic32_dmt_stop(struct watchdog_device *wdd)
 133 {
 134         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 135
 136         dmt_disable(dmt);
 137
 138         return 0;
 139 }
 140
 141 static int pic32_dmt_ping(struct watchdog_device *wdd)
 142 {
 143         struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
 144
 145         return dmt_keepalive(dmt);
 146 }
 147
 148 static const struct watchdog_ops pic32_dmt_fops = {
 149         .owner          = THIS_MODULE,
 150         .start          = pic32_dmt_start,
 151         .stop           = pic32_dmt_stop,
 152         .ping           = pic32_dmt_ping,
 153 };
 154
 155 static const struct watchdog_info pic32_dmt_ident = {
 156         .options        = WDIOF_KEEPALIVEPING |
 157                           WDIOF_MAGICCLOSE,
 158         .identity       = "PIC32 Deadman Timer",
 159 };
 160
 161 static struct watchdog_device pic32_dmt_wdd = {
 162         .info           = &pic32_dmt_ident,
 163         .ops            = &pic32_dmt_fops,
 164 };
 165
 166 static int pic32_dmt_probe(struct platform_device *pdev)
 167 {
 168         struct device *dev = &pdev->dev;
 169         int ret;
 170         struct pic32_dmt *dmt;
 171         struct watchdog_device *wdd = &pic32_dmt_wdd;
 172
 173         dmt = devm_kzalloc(dev, sizeof(*dmt), GFP_KERNEL);
 174         if (!dmt)
 175                 return -ENOMEM;
 176
 177         dmt->regs = devm_platform_ioremap_resource(pdev, 0);
 178         if (IS_ERR(dmt->regs))
 179                 return PTR_ERR(dmt->regs);
 180
 181         dmt->clk = devm_clk_get_enabled(dev, NULL);
 182         if (IS_ERR(dmt->clk)) {
 183                 dev_err(dev, "clk not found\n");
 184                 return PTR_ERR(dmt->clk);
 185         }
 186
 187         wdd->timeout = pic32_dmt_get_timeout_secs(dmt);
 188         if (!wdd->timeout) {
 189                 dev_err(dev, "failed to read watchdog register timeout\n");
 190                 return -EINVAL;
 191         }
 192
 193         dev_info(dev, "timeout %d\n", wdd->timeout);
 194
 195         wdd->bootstatus = pic32_dmt_bootstatus(dmt) ? WDIOF_CARDRESET : 0;
 196
 197         watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
 198         watchdog_set_drvdata(wdd, dmt);
 199
 200         ret = devm_watchdog_register_device(dev, wdd);
 201         if (ret)
 202                 return ret;
 203
 204         platform_set_drvdata(pdev, wdd);
 205         return 0;
 206 }
 207
 208 static const struct of_device_id pic32_dmt_of_ids[] = {
 209         { .compatible = "microchip,pic32mzda-dmt",},
 210         { /* sentinel */ }
 211 };
 212 MODULE_DEVICE_TABLE(of, pic32_dmt_of_ids);
 213
 214 static struct platform_driver pic32_dmt_driver = {
 215         .probe          = pic32_dmt_probe,
 216         .driver         = {
 217                 .name           = "pic32-dmt",
 218                 .of_match_table = of_match_ptr(pic32_dmt_of_ids),
 219         }
 220 };
 221
 222 module_platform_driver(pic32_dmt_driver);
 223
 224 MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@microchip.com>");
 225 MODULE_DESCRIPTION("Microchip PIC32 DMT Driver");
 226 MODULE_LICENSE("GPL");