drivers/watchdog/rza_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Renesas RZ/A Series WDT Driver
   4  *
   5  * Copyright (C) 2017 Renesas Electronics America, Inc.
   6  * Copyright (C) 2017 Chris Brandt
   7  */
   8
   9 #include <linux/bitops.h>
  10 #include <linux/clk.h>
  11 #include <linux/delay.h>
  12 #include <linux/module.h>
  13 #include <linux/of_address.h>
  14 #include <linux/of_device.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/watchdog.h>
  17
  18 #define DEFAULT_TIMEOUT         30
  19
  20 /* Watchdog Timer Registers */
  21 #define WTCSR                   0
  22 #define WTCSR_MAGIC             0xA500
  23 #define WTSCR_WT                BIT(6)
  24 #define WTSCR_TME               BIT(5)
  25 #define WTSCR_CKS(i)            (i)
  26
  27 #define WTCNT                   2
  28 #define WTCNT_MAGIC             0x5A00
  29
  30 #define WRCSR                   4
  31 #define WRCSR_MAGIC             0x5A00
  32 #define WRCSR_RSTE              BIT(6)
  33 #define WRCSR_CLEAR_WOVF        0xA500  /* special value */
  34
  35 /* The maximum CKS register setting value to get the longest timeout */
  36 #define CKS_3BIT                0x7
  37 #define CKS_4BIT                0xF
  38
  39 #define DIVIDER_3BIT            16384   /* Clock divider when CKS = 0x7 */
  40 #define DIVIDER_4BIT            4194304 /* Clock divider when CKS = 0xF */
  41
  42 struct rza_wdt {
  43         struct watchdog_device wdev;
  44         void __iomem *base;
  45         struct clk *clk;
  46         u8 count;
  47         u8 cks;
  48 };
  49
  50 static void rza_wdt_calc_timeout(struct rza_wdt *priv, int timeout)
  51 {
  52         unsigned long rate = clk_get_rate(priv->clk);
  53         unsigned int ticks;
  54
  55         if (priv->cks == CKS_4BIT) {
  56                 ticks = DIV_ROUND_UP(timeout * rate, DIVIDER_4BIT);
  57
  58                 /*
  59                  * Since max_timeout was set in probe, we know that the timeout
  60                  * value passed will never calculate to a tick value greater
  61                  * than 256.
  62                  */
  63                 priv->count = 256 - ticks;
  64
  65         } else {
  66                 /* Start timer with longest timeout */
  67                 priv->count = 0;
  68         }
  69
  70         pr_debug("%s: timeout set to %u (WTCNT=%d)\n", __func__,
  71                  timeout, priv->count);
  72 }
  73
  74 static int rza_wdt_start(struct watchdog_device *wdev)
  75 {
  76         struct rza_wdt *priv = watchdog_get_drvdata(wdev);
  77
  78         /* Stop timer */
  79         writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
  80
  81         /* Must dummy read WRCSR:WOVF at least once before clearing */
  82         readb(priv->base + WRCSR);
  83         writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
  84
  85         rza_wdt_calc_timeout(priv, wdev->timeout);
  86
  87         writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
  88         writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT);
  89         writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME |
  90                WTSCR_CKS(priv->cks), priv->base + WTCSR);
  91
  92         return 0;
  93 }
  94
  95 static int rza_wdt_stop(struct watchdog_device *wdev)
  96 {
  97         struct rza_wdt *priv = watchdog_get_drvdata(wdev);
  98
  99         writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
 100
 101         return 0;
 102 }
 103
 104 static int rza_wdt_ping(struct watchdog_device *wdev)
 105 {
 106         struct rza_wdt *priv = watchdog_get_drvdata(wdev);
 107
 108         writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT);
 109
 110         pr_debug("%s: timeout = %u\n", __func__, wdev->timeout);
 111
 112         return 0;
 113 }
 114
 115 static int rza_set_timeout(struct watchdog_device *wdev, unsigned int timeout)
 116 {
 117         wdev->timeout = timeout;
 118         rza_wdt_start(wdev);
 119         return 0;
 120 }
 121
 122 static int rza_wdt_restart(struct watchdog_device *wdev, unsigned long action,
 123                             void *data)
 124 {
 125         struct rza_wdt *priv = watchdog_get_drvdata(wdev);
 126
 127         /* Stop timer */
 128         writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
 129
 130         /* Must dummy read WRCSR:WOVF at least once before clearing */
 131         readb(priv->base + WRCSR);
 132         writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
 133
 134         /*
 135          * Start timer with fastest clock source and only 1 clock left before
 136          * overflow with reset option enabled.
 137          */
 138         writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
 139         writew(WTCNT_MAGIC | 255, priv->base + WTCNT);
 140         writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, priv->base + WTCSR);
 141
 142         /*
 143          * Actually make sure the above sequence hits hardware before sleeping.
 144          */
 145         wmb();
 146
 147         /* Wait for WDT overflow (reset) */
 148         udelay(20);
 149
 150         return 0;
 151 }
 152
 153 static const struct watchdog_info rza_wdt_ident = {
 154         .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
 155         .identity = "Renesas RZ/A WDT Watchdog",
 156 };
 157
 158 static const struct watchdog_ops rza_wdt_ops = {
 159         .owner = THIS_MODULE,
 160         .start = rza_wdt_start,
 161         .stop = rza_wdt_stop,
 162         .ping = rza_wdt_ping,
 163         .set_timeout = rza_set_timeout,
 164         .restart = rza_wdt_restart,
 165 };
 166
 167 static int rza_wdt_probe(struct platform_device *pdev)
 168 {
 169         struct device *dev = &pdev->dev;
 170         struct rza_wdt *priv;
 171         unsigned long rate;
 172         int ret;
 173
 174         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 175         if (!priv)
 176                 return -ENOMEM;
 177
 178         priv->base = devm_platform_ioremap_resource(pdev, 0);
 179         if (IS_ERR(priv->base))
 180                 return PTR_ERR(priv->base);
 181
 182         priv->clk = devm_clk_get(dev, NULL);
 183         if (IS_ERR(priv->clk))
 184                 return PTR_ERR(priv->clk);
 185
 186         rate = clk_get_rate(priv->clk);
 187         if (rate < 16384) {
 188                 dev_err(dev, "invalid clock rate (%ld)\n", rate);
 189                 return -ENOENT;
 190         }
 191
 192         priv->wdev.info = &rza_wdt_ident,
 193         priv->wdev.ops = &rza_wdt_ops,
 194         priv->wdev.parent = dev;
 195
 196         priv->cks = (u8)(uintptr_t) of_device_get_match_data(dev);
 197         if (priv->cks == CKS_4BIT) {
 198                 /* Assume slowest clock rate possible (CKS=0xF) */
 199                 priv->wdev.max_timeout = (DIVIDER_4BIT * U8_MAX) / rate;
 200
 201         } else if (priv->cks == CKS_3BIT) {
 202                 /* Assume slowest clock rate possible (CKS=7) */
 203                 rate /= DIVIDER_3BIT;
 204
 205                 /*
 206                  * Since the max possible timeout of our 8-bit count
 207                  * register is less than a second, we must use
 208                  * max_hw_heartbeat_ms.
 209                  */
 210                 priv->wdev.max_hw_heartbeat_ms = (1000 * U8_MAX) / rate;
 211                 dev_dbg(dev, "max hw timeout of %dms\n",
 212                         priv->wdev.max_hw_heartbeat_ms);
 213         }
 214
 215         priv->wdev.min_timeout = 1;
 216         priv->wdev.timeout = DEFAULT_TIMEOUT;
 217
 218         watchdog_init_timeout(&priv->wdev, 0, dev);
 219         watchdog_set_drvdata(&priv->wdev, priv);
 220
 221         ret = devm_watchdog_register_device(dev, &priv->wdev);
 222         if (ret)
 223                 dev_err(dev, "Cannot register watchdog device\n");
 224
 225         return ret;
 226 }
 227
 228 static const struct of_device_id rza_wdt_of_match[] = {
 229         { .compatible = "renesas,r7s9210-wdt",  .data = (void *)CKS_4BIT, },
 230         { .compatible = "renesas,rza-wdt",      .data = (void *)CKS_3BIT, },
 231         { /* sentinel */ }
 232 };
 233 MODULE_DEVICE_TABLE(of, rza_wdt_of_match);
 234
 235 static struct platform_driver rza_wdt_driver = {
 236         .probe = rza_wdt_probe,
 237         .driver = {
 238                 .name = "rza_wdt",
 239                 .of_match_table = rza_wdt_of_match,
 240         },
 241 };
 242
 243 module_platform_driver(rza_wdt_driver);
 244
 245 MODULE_DESCRIPTION("Renesas RZ/A WDT Driver");
 246 MODULE_AUTHOR("Chris Brandt <chris.brandt@renesas.com>");
 247 MODULE_LICENSE("GPL v2");